Flat roof for a private house: a general overview of construction technology. Houses with a flat roof - selection of materials and technology for implementing roofing work (70 photos) Advantages of a flat roof of multi-storey buildings
Unisex Sneakers Swimming Shoes Water Sports Aqua Seaside…
612.33 rub.
Free shipping★★ ★★ ★★ ★★ ★★ (4.80) | Orders (1151)
Houses with a flat roof - options and projects
Recently, interest in projects has been growing low-rise buildings with a flat roof. Architects and developers are attracted to these unusual buildings, where you can equip an observation deck or even set up a real hanging garden. Of course, in practice everything turns out to be more complicated than in theory.
Designing a flat roof raises many questions regarding its cost, choice of materials for insulation and waterproofing, organization of water flow, maintenance and operation of the roof. Finding answers to them is not so easy. The fact is that domestic private companies working in the field of cottage and country house construction are well familiar with the most popular design - pitched, but, as a rule, they have no experience in constructing flat roofs, which are designed completely differently.
Which roof will be cheaper?
What immediately attracts attention is the fact that the area flat roof less than a pitched one, which means less materials will be required, and the work will be cheaper. However, this statement is only true for regions with a warm climate and low snow load, especially if we are talking about an unused roof. In central Russia, to ensure the reliability and durability of a horizontal roof, it is necessary to apply rather expensive engineering solutions.
It turns out that 1 m 2 of a flat concrete or steel base, the bearing capacity of which will allow it to withstand the weight of snow cover, costs 2-2.5 times more than a wooden one beam structure pitched roof. The difference in the volumetric consumption of insulation is leveled due to the fact that a flat roof requires more expensive material high density. There is still hope to save on roofing, however, modern polymer membranes - the optimal waterproofing for horizontal roofs - are no cheaper (and sometimes much more expensive) than flexible tiles.
There is no need to install snow guards, but you cannot do without a roof hatch and a drainage system. If you try to cut costs according to the estimate, you will subsequently have to pay the price of having to repair the roof every 10-15 years.
Finally, it should be taken into account that flat roofs are appropriate only on houses of modern architecture - with a large glazing area and complex finishing with the latest facade materials. That and the other one won't be cheap at all.
Flat roof covering
As a rule, in low-rise housing construction, the flat roofing is a prefabricated or monolithic reinforced concrete slab.
Reinforced concrete slabs (PB, hollow PC, PV, etc.) are capable of covering a span of up to 9 m in length and can withstand a pressure of 8, 9 or 12.5 kPa (this value is indicated by the last digit in the product labeling). They can serve as a “base” for any roofing pies, including top layer from paving slabs or fertile soil. However, to install the structure, it will be necessary to ensure that a truck crane can enter the site (while steel beams and flooring can be easily lifted using winches). The depth of support of the ceiling on the wall depends on the material of the latter - for example, for brick this parameter should be equal to the thickness of the slab. Before proceeding with the installation of the roof, it is important to seal the joints of the elements with mortar and additionally seal them with elastic polymer tape. Monolithic w\6 ceiling is erected from heavy concrete using removable (for example, from OSB boards on jack stands) or permanent (from corrugated sheeting) formwork. It is reinforced with a two- or four-level welded frame made of rods with a diameter of 12 mm. The dimensions of a monolithic slab are not regulated (unlike a prefabricated one), which provides the architect with freedom when designing a building; other advantages are the absence of seams, the comparative simplicity of the installation of passage units (chimney, ventilation ducts) and high load-bearing capacity (subject to compliance with technological regulations).
Beam floor
In principle, when constructing a floor, you can use a combination of beams (wooden, steel) and load-bearing corrugated sheeting. However, experts do not recommend using wooden beams (with the exception of those made of LVL beams with a cross-section of 200 * 100 mm) in regions where the snow pressure exceeds 1.2 kPa (about 120 kgf/m2) - that is, in most of the territory of the Russian Federation. A roof covering made of steel I-beams and corrugated sheets with a wave height of 60 mm and a wall thickness of 0.7 mm allows you to cover a span of up to 12 m and can withstand a pressure of at least 6 kPa. But in general, it is less durable than concrete, and is relatively rarely used in individual construction. It makes more sense to use corrugated sheeting as permanent formwork, which, by the way, does not replace the need to build a reinforcement frame.
Types of flat roof
In the low-rise sector, mostly flat roofs without attics are in demand, because the attic requires additional costs and disrupts the architectural proportions of the house. This means that the roof must protect against winter cold and summer heat. A common feature of flat roofs is that the heat-insulating layer is located on top of the supporting structure (in pitched roofs it is usually located between the rafters). If you insulate the room from below, the dew point may shift into the thickness of the ceiling, which will lead to a reduction in the service life of the latter.
There are special requirements for thermal insulation for flat roofs. The material must not only have a low thermal conductivity coefficient, but also have good resistance to mechanical loads - both distributed (pressure from the overlying layers of roofing cake, equipment, snow) and local ones that arise during installation. In addition, it is important that the material has hydrophobic properties and is non-flammable. At the moment, there are several ways to install thermal insulation: using mechanical fasteners, adhesive and free laying. In addition to traditional two-layer insulation, single-layer installation is becoming an increasingly popular solution.
As for roofing options, there are dozens of them. Suffice it to say that more than 40 “recipes” are given in SP 17.13330.2011 alone. At the same time, coating and insulation manufacturing companies are offering more and more new engineering solutions. However, they are always based on one of two circuit diagrams- traditional or inversion.
Traditional flat roof design V general outline is: on top load-bearing base a vapor barrier film is laid (polypropylene, polyethylene, titum-polymer), followed by insulation, for example, mineral wool slabs with a compressive strength at ten percent deformation of at least 30 kPa, in one or two layers with a total thickness of 200 mm. Located above separation layer(for example, from a polyethylene film), along which a reinforced slope-forming screed is poured (a flat roof must be given a slope of 2-3% towards the center or edges to ensure water drainage). The dried screed serves as the basis for a roll or mastic waterproofing coating.
Other options are also possible.
For example, a slope-forming screed can be located at the very bottom of the pie; in this case, the roof waterproofing is fixed with gravel ballast, paving slabs on supports or special dowels. Some materials, say the “RUF SLOPE” system (Rockwool) or “TechnoNIKOL Slope”, allow you to do without a screed altogether: the slabs have variable thickness, and with their help it is not difficult to create smooth changes in level to ensure water drainage.
Flat roofs are divided into unexploited and exploited. The former visit only for inspection, prevention and repair; for this purpose, a roof hatch is installed, to which it leads attic staircase. The roof in use in cottages most often serves as a terrace, that is, a durable wear-resistant coating must be laid on it, and the load-bearing base is designed for increased loads. A type of exploitation is a roof with landscaping, laid with a turf layer on top of the main thermal-hydro-insulating pie; Usually there are paths and a recreation area on it. A convenient exit to the roof in use should be provided, for example from a vestibule superstructure.
Inversion roof it is designed differently: in it, insulation resistant to constant exposure to water (usually extruded polystyrene foam - EPPS) is located on top of the waterproofing. At the same time, the latter is reliably protected from mechanical damage and is located in the positive temperature zone (freezing-thawing cycles are destructive for almost any material). It is easy to turn an inversion roof into a usable one, for example, by covering the insulation with a drainage layer of sand and gravel and laying paving slabs. The disadvantages of the design include more complex drainage. However, we need to talk about gutters separately.
For roofs in use, as well as roofs installed in regions with harsh climatic conditions, the inversion scheme is ideal. Since the waterproofing layer is located under the thermal insulation layer, it is protected from mechanical stress, as well as from temperature changes and UV radiation, which significantly extends its service life roofing system. Waterproofing materials based on modified bitumen must be laid in at least two layers - this technology is more common, and in addition, it allows you to level out possible errors when fusing the material. One layer is enough for a polymer membrane, and reliability is ensured by automatic welding equipment, which greatly increases the speed of work. In addition, when installing a polymer membrane, an open flame is not used, so the technology is considered safer.
Rolled materials based on modified bitumen, as a rule, are fused with a gas burner (a), and it is difficult to prevent small flaws that can cause leakage (if there is no second layer). The quality of welding of PVC coating strips (6) is much easier to control
Flat roof drainage and waterproofing system
The flat roof is equipped with a parapet (attic) 30-90 cm high, which helps ensure organized drainage of water; on a roof in use it also serves as a safety fence. At the same time, the design of gutters should be approached very responsibly, because if you make a mistake, a huge puddle can form above your head, which can lead to leaks and damage to supporting structures.
As a rule, the choice is made in favor of an internal drain. Such a system is less exposed to the atmosphere and is therefore more durable and reliable than an external one. Let's talk in more detail about its main elements. Water intake funnels are installed on low areas of the roof. As a rule, on roofs with an area of up to 150 m2, two funnels are installed - the main one, connected to the riser, and the emergency one, with water discharged through a hole in the parapet. With an increase in the number of funnels and risers, the reliability of the system increases, but its cost also increases.
Flat roofs are in demand in modular construction. Among the advantages of this method are the affordable cost and high speed of construction of housing, as well as the possibility of gradually increasing its area
For inversion and green roofs, special funnels with drainage rings have been developed to collect moisture from the intermediate layers. Additional receivers must be equipped with electrical heating on the base self-regulating cable- then they will begin to properly perform their function during alternating thaws and frosts.
In a new type of system, the so-called siphon-vacuum system, special funnels are used to prevent air from being sucked into the water flow. Thanks to them, the speed of fluid movement in the pipe (and hence the throughput of the latter) increases, which makes it possible to reduce the diameter of the system elements. However, for low-rise buildings, the savings turn out to be insignificant; moreover, such systems require more accurate calculations than gravity systems.
The drain riser is made from sewer pipes- polypropylene, polyvinyl chloride, and it makes sense to use sound-absorbing products, for example RAUPIANO Plus (REHAU), or soundproof the riser, otherwise you will hear the murmur of water for hours. The riser is connected to the funnel using an elastic coupling. When laying pipes, the number of bends and the length of horizontal sections, which reduce the throughput of the system, should be minimized. A drainage pipe laid in the basement or insulated underground connects the riser to the rainwater drainage system or ensures the discharge of water into a linear drainage tray.
In the second case, there is a risk of clogging the outlet with ice, so the riser should be equipped with a “winter” outlet to the domestic sewer (the latter should be equipped with a water seal). The outlet pipe is cleaned through a collapsible connection or an inspection module.
When choosing the standard size of elements of a traditional gravity system, they proceed from the intensity of rain in a given area, focusing on SP 32.13330.2012.
The external drainage system is more vulnerable than the internal one, and also affects the appearance of the facades, but does not require holes in the roof and ceilings and does not eat up usable area Houses. Water is discharged through parapet funnels or pipes embedded in the parapet, under which classic funnels are installed (as on pitched roof) and down pipes attached to the walls with brackets. When calculating, it is assumed that for every square meter of roof area there should be 1-1.5 cm of the cross-section of drainpipes. Elements outdoor system can be made of PVC, steel, copper, zinc-titanium.
Flat roof landscaping
Since ancient times, turf-covered roofs have been used in countries with moderately cold and humid climates, and the green carpet performed the main moisture-protective function in them.
As part of the modern concept of a green roof, a layer of fertile soil with plants is needed to give unusual features to the appearance of the building, decorate the terrace roof and extend the life of the coating by protecting it from ultraviolet rays. In addition, it absorbs rainwater, unloading gutters, dampens the sound of rain, protects the upper floor rooms from overheating in the summer and reduces heat loss in the winter. It is believed that landscaping almost doubles the life of a roof. Its disadvantages include increased load on bearing structures buildings and increasing construction costs.
In addition, a green carpet needs care, the intensity of which depends on the selected plant species. If you do not pay due attention to the plants, they will freeze and die from drought.
To green the roof, you should lay on top of the main waterproofing layer (in an inversion scheme - on top of the insulation) an additional cake made of materials that will ensure protection of the waterproofing layer from roots, filtration and drainage of rainwater. For these purposes, special films, dense geotextiles, gravel bedding or drainage and moisture storage membranes made of high-density polyethylene, for example PLANTER GEO or Delta-Floraxx, are used.
Then a mixture of minerals and fertilizers is poured - the so-called soil substrate. You can prepare it yourself by adding fine expanded clay (5-15%), sand (about 20 96) and fertilizers to a light soil mixture of neutral peat. As for plants, the easiest way is to limit yourself to meadow forbs and drought-resistant ground covers - sedum, herbaceous carnation, thyme.
They do not need to organize an irrigation system, and the thickness of the soil layer can be only 6-12 cm (this type of roof is called extensive). If you plan to walk along the roof among ornamental shrubs, you will have to provide watering and increase the soil thickness to 20-40 cm. Such a roof is called intensive; it creates a significant additional load on the floor, so it must be provided for at the design stage of the building.
Which coating is better to choose for a flat roof?
Sheet and piece coverings are unsuitable for flat roofs: water will inevitably seep through the joints of the elements. Therefore, roll materials and mastics are used. Let us give a brief description of them.
ROLL REINFORCED POLYMER-BITUMEN ROOF.
The mechanical strength of these materials is several times higher than that of roofing cardboard (roofing felt, roofing felt). And modifying additives increase resistance to moisture, air and ultraviolet radiation. The material is glued to the base with mastic, fixed mechanically or (most often) fused. There are coatings for the lower layers of the roof (Tekhnoelast EPP, Uniflex EPP, Bireplast TPP, etc.) and for the upper ones (Tekhnoelast EKP, Uniflex EKP, Gidrostekloizol TKP, etc.). The latter are sprinkled with mineral chips, which reduce the risk of fire and additionally protect against mechanical damage and UV exposure. The cost of waterproofing of both types is low - from 65 and from 150 rubles, respectively. per 1 m 2 and the average service life of a roofing carpet is 15-30 years.
ROLL PVC MEMBRANES, for example, Sikaplan WP, Logicroof, Ecoplast are strong and durable (up to 30 years without repair) and do not support combustion. However, they require professional approach for installation (the joints of the strips must be carefully welded with hot air) and are relatively expensive - from 320 rubles. for 1 m 2. It is important to consider that this material does not tolerate contact with bitumen.
ROOF COVERING OPTIONS
Traditional with external drain
1 - overlap; 2 - slope-forming screed; 3 - vapor barrier; D, 5 - mineral wool insulation; 6 - waterproofing; 7 - drain
Inversion
with internal drain
1 - screed; 2 - PVC membrane; 3 - EPPS; 4 - funnel with drainage ring; 5 - drainage membrane; 6 - sand; 7 - paving slabs
A flat roof is a common architectural solution in civil, industrial and private construction. The construction of a flat roof has its own characteristics, but the main principle is that the waterproofing layer should be a continuous carpet with certain technical characteristics. The design of roofing structures must be carried out in accordance with current SNiP.
Roofing pie structure
If you look at the structure in cross-section, this type of roof is a multi-layer structure, which includes:
The base of a flat roof can be a reinforced concrete floor slab or a metal profile structure. Depending on the type of base, the material for the remaining components of the roofing cake and methods of its installation are selected.
The vapor barrier layer is made from rolled or bituminous materials. It prevents the penetration of moisture from the premises into the thermal insulation layer of the roof structure.
A wide range of materials are used as insulation for flat roofs, including:
- mineral wool;
- expanded clay gravel;
- polystyrene foam boards;
- cement-sand screed.
The waterproofing layer is traditionally made from roll materials on a bitumen basis. Special mastics or a PVC membrane can also be used.
A waterproofing carpet must have a certain elasticity in order to withstand mechanical deformations of the base and temperature changes.
The structure of the pie depends on functional features roofs. The following types of roofing differ:
Flat roof slope
According to SNiP, when installing a flat roof structure, it is necessary to provide for its slope of 1-4°. This design of flat roofs avoids the accumulation of water on the surface of the covering. It is not only prolonged stagnation of water in certain areas that is dangerous for waterproofing. Severe deformation and destruction of the outer covering of the roof is a consequence of repeated repetition of the process of freezing and thawing of accumulated moisture. Various materials can be used to pitch the roof. The choice depends on their technical characteristics and installation features.
Lightweight concrete with loose polymer filler (in particular, extruded polystyrene) is one of the popular materials. It is quite easy to install, and the resulting structure is highly durable. But the use of this material for leveling should be considered at the building design stage, since the significant weight of the concrete used increases the load on the floor, walls and foundation of the building.
Lightweight concrete filled with perlite or expanded clay has similar characteristics. This material is cheaper, but its weight is even greater, and the resulting roofing pie less durable.
The installation of a flat roof can be carried out using monolithic insulation, allowing for slope. In this case, sheet material (mineral wool, expanded clay sheets, etc.) is mounted on the prepared surface. Fastening can be done with strong, tenacious glue, which prevents the sheets from moving over time. Dowels with a plastic spacer can also be used - it is advisable to exclude metal contact with the base of the roof so that the roofing cake does not have cold bridges.
The most labor-intensive is the installation of a roof using bulk materials for leveling. Difficult to pour concrete layer bulk insulation(expanded clay or perlite), observing the required angle of inclination of the roof plane, since the granules can move.
An effective, but expensive option for degrading is laying foam concrete followed by applying a layer of fiber-reinforced concrete. A cake with such a heat-insulating layer is designed for long-term operation. This technology requires the involvement of experienced specialists.
In accordance with SNiP, the slope of the roof is towards the water inlet funnels (if there is an internal drain), or towards the water inlet gutters external system catchment, which should be mounted under the roofing carpet or on the outer wall of the building.
Roofing units
In order for the roofing pie to be reliably protected from external influences, special attention should be paid to the places where it adjoins building structures - parapets, walls, pipes, external parts of ventilation systems, etc. There are various nodes of a flat roof, first of all, this is the node:
- adjacencies;
- overhang;
- passage through the roof.
The units are installed on a reinforced concrete base in places where the roofing pie meets the vertical structure with a cut. Manufacturers of roofing materials often develop their own systems, which may have certain design features.
The unit must ensure the tightness of the joint and its thermal protection, therefore the installation of the units should be treated with the utmost care.
Installation of an unused flat roof
The most common design is traditional soft roof. In cross-section, it consists of a load-bearing base slab, a vapor barrier layer, thermal insulation made of sheet mineral wool and a waterproofing carpet made of rolled bitumen-containing material. The advantages of this design include low cost and simple installation.
More practical non-exploited roofs are made using modern materials. PVC membrane waterproofing is very popular. Its installation can be carried out in any season, since the membrane is resistant to low and high temperatures. In addition, if the thermal insulation layer has managed to accumulate moisture during the installation process, the membrane allows it to evaporate. At the same time, the material has high water-repellent properties. In the process of installing the panels into a single whole, special welding equipment without an open flame is used.
Covering an unused flat roof can be done using mastic. This is a liquid material that is applied on top of a rigid, even thermal insulation layer. The mastic is made on the basis of elastic, hydrophobic polyurethane resins. On outdoors, after a certain time after application in an even layer, it polymerizes, forming a continuous rubber-like membrane. The installation of such waterproofing allows you to reliably protect the roofing pie from moisture penetration.
A popular technology is the use of built-up waterproofing. This affordable option in terms of price and quality ratio - the durability of such a roof is from 25 years. A bitumen-polymer material based on a fabric that is not subject to rotting creates a super-strong waterproofing layer. Using this material it is possible to install serviceable roofs.
Construction of a serviceable roof
This flat roof design is much more expensive to install, but makes it possible to profitably use additional space. Today this type of roofing is widely in demand for equipment sports grounds, green areas, cafes, parking lots, etc. Installation of a reinforced roof is also necessary if heavy objects, including equipment, are to be installed on the roof. In accordance with SNiP, the roofing structure must withstand uneven high loads, that is, not deform in limited areas of the area. The section of a flat roof in use differs from the usual one in the presence of a rigid base or a special screed on top of the waterproofing layer. This coating prevents the waterproofing carpet from being pushed through with its subsequent destruction.
Features of inversion coating
The structure of an inversion roof is fundamentally different from other types of roofs. When arranging it, first of all, a waterproofing layer is mounted on the base. In cross-section, the roofing pie looks like this: base slab, waterproofing, insulation, drainage layer, geotextile. This design allows you to protect the waterproofing material from the destructive effects of ultraviolet radiation, temperature changes, and mechanical damage. Geotextiles, in turn, provide protection for the insulation. Paving slabs are used as the outer layer. Such a roof can withstand high loads, including being used as a parking lot.
It is required to approach the installation of the waterproofing layer as carefully as possible, since in order to correct errors it will be necessary to open the ballast layers.
The installation of a traditional roofing structure can be done independently, but for the installation of flat roofs using modern materials and technologies, it is recommended to involve specialists who have the necessary equipment.
Flat roof installation: design and components
The device of a flat roof and its design. The main components and composition of the roofing pie in section. SNiP for the structure and slope of flat roofs
Flat roof installation
Many people associate a flat roof with urban high-rise buildings. And very few people draw in their imagination Vacation home with a flat roof, which combines saving precious space and the possibility of creating luxurious places to relax on the roof.
Flat roof pie.
In the age of modern building materials and new technologies, it is possible to successfully build private houses with a flat roof, without fear of the surprises of our unpredictable climate. But the full extent of pleasure from a flat roof can only be experienced when the builders and the customer himself listen carefully to the advice of a specialist in installation technology and the selection of the necessary components of the roof structure. Only under such conditions will a flat roof serve for a long time for more than one generation of the inhabitants of the house, without requiring additional costs.
What are the advantages of flat roof designs?
Until recently, various designs and parts for flat roofing were either very expensive or not reliable and functional enough, which did not at all benefit the popularization of roofs of this type, especially for private developers.
However, life experience proves that, being under the influence of stereotypes, we are too biased towards many problems, as a result of which we do not always judge things objectively. The main thing is from many existing options choose the most adequate and correct one to avoid mistakes.
According to architects, buildings in the spirit of constructivism, which brings a minimum of details and simplicity of design, are now becoming fashionable again. As a result, the attitude of customers towards flat roofing is changing for the better. In Europe, the design of flat roofing houses is called a fashionable architectural feature of the project. A house with a roof without slopes looks more modern.
Flat roof installation diagram.
Until recently, a flat roof was a complete taboo for most consumers. According to some, it was simply tasteless, others were afraid of heavy precipitation in the form of snow, others believed that a flat roof was an undertaking that required prohibitive amounts of money. financial costs. Nevertheless, experts cite a lot of obvious advantages for buildings with this design:
- In most cases, a flat roof is equipped as a green recreation area.
- Saving material, because the area of the flat coating less area pitched with the same architectural basis.
- Laying a flat roof is much more convenient than a pitched roof - it is easier to install the covering under your feet rather than in an unsafe position at a high altitude.
- Maintaining flat roofs is not an extreme mountaineering activity, but rather a routine procedure.
- Plus, the design of flat roofs makes it possible to obtain additional space without increasing the outline of the structure.
By the way, in developed countries, the possibility of using a flat roof is most relevant in megacities. Here, the problem of ecology has increasingly come to the fore, and therefore raising elements of gardens, parks, vegetable gardens and lawns from the ground to the clouds has become a very popular thing. And the most important thing is that if you want your flat roof to be reliable protection, it must be properly installed using durable modern building materials.
Components of a flat roof
Typically, a flat roof is based on a load-bearing base (it can be a reinforced concrete slab or profiled a metal sheet), on which heat-insulating material is laid over a vapor barrier layer, which is protected from precipitation by a waterproofing layer.
Scheme of an inversion flat roof.
It is characteristic that all components of the roofing “pie” are of equal importance, and if at least one of them is unsuitable, the entire structure will be damaged. The basis of the work on installing a flat roof is an integrated approach, which consists of determining the type of coating and implementing the best design solution when considering all operational and technological properties, such as fire resistance, water resistance, ease of maintenance, labor costs during installation, aesthetic qualities, etc.
Specialists pay special attention to sealing seams, choosing fastening methods and elements, arranging technological components of the coating (junctions to parapets and pipes, drains, corners, superstructures, etc.) and performing through holes. And it goes without saying that the operation of the roof will not depend on any damaging factors if the various components of the structure are made of impact-resistant and weather-resistant materials that are resistant to corrosion processes and exposure to UV rays. Excluding even one detail from the overall system is fraught with the most undesirable consequences.
Depending on the type of waterproofing, it can be glued, mechanically secured, or loosely laid. Much attention should be paid to the quality of fasteners and the method of their installation, especially for materials that are laid to the base of the roof with mechanical fastening.
If the rules for laying roofing are neglected, the following undesirable consequences may occur:
- Breakdown of waterproofing by strong gusts of wind.
- Loss of the bearing capacity of the base due to electrochemical corrosion in the “wrong screw + corrugated sheet” system.
- A clogged or frozen funnel, causing the roof to fill with moisture and leaks.
The roofing “pie” consists of the following layers (from bottom to top):
Insulation of a flat roof
Types of flat roof insulation: one, two and three layers.
The base of a flat roof is a load-bearing slab made of monolith, reinforced concrete or corrugated metal sheet. On top it is covered with a vapor barrier material, which protects the insulation from water vapor, thus preventing it from swelling from getting wet and ensuring the preservation of all properties. After this, thermal insulation is installed on the roof, which, in turn, is covered with a waterproofing carpet to protect it from precipitation.
For a flat roof, there are one- and two-layer thermal insulation systems. Nowadays, a two-layer system is more often used in construction. It works like this: the bottom layer, 70-200 mm thick, is assigned the main function of thermal insulation, while the top layer, which is 30-50 mm, is responsible for the redistribution of mechanical loads. Despite the smaller thickness, the second layer is more durable and has a higher density. This distribution of flat roof covering layers makes it possible to significantly reduce its weight and, thereby, the load on the floors. The insulation must meet the following requirements:
- Low thermal conductivity and water absorption.
- Fire safety.
- High vapor permeability.
- Compressive and peel strength of layers.
Drainage device
Diagram of a drainage system on a flat roof.
When installing roofs, it is very important to ensure the free escape of wet vapors from the roof covering. Ventilation accessories are necessary elements of a modern roof. As a result of human activity, water vapor is continuously generated inside the building. Due to the convective process and diffusion, it rises upward and, when cooled, condenses in the space under the roof. This process is especially intense in winter. It negatively affects roof elements - both wooden and metal. If too much condensation accumulates, wet spots form on the ceiling and mold develops. In addition, moisture accumulating in the thermal insulation material reduces its properties, which leads to increased costs for heating the room. To avoid such situations, you need to take care of the proper removal of moisture from the outside of the building.
This task is best accomplished by special roofing components - a roof fan, otherwise called an aerator. The aerator consists of pipes different diameters made of plastic or metal, which are covered with umbrella-shaped caps.
The operation of the aerator is based on the pressure difference caused by the flow of air masses. Its design allows moisture vapor to be removed from under the roofing without damaging the latter.
On flat roofs, aerators are placed evenly over the entire surface in the most high points roof plane at the junction of thermal insulation boards with each other. It is advisable to install aerators at the same time as the roof itself. Otherwise, the cost of installing ventilation increases significantly.
There are a large number of components for installing a flat roof. The need for their use is determined by the design of the roof. For example, in Western countries, much attention is paid to equipping roofs with natural smoke removal devices, which enable people to safely leave the building in the event of a fire.
The reliability of the roof also depends on its slope. There are no completely flat roofs, because to drain water you need, albeit a very small, slope. For a flat roof it is measured as a percentage.
It is not advisable to install roofs with a slope of less than 2 percent. The best option is a slope of 2.5 percent. In this case, the structure is freed from water in a short time, providing more comfortable conditions for the functioning of the roofing material. Even with a good slope small defect in roofing will be insignificant.
Another important element of the roof is gutters, which “carry away” moisture and snow along a given route. On a flat roof, an internal drainage system is most often installed. Special drainage funnels or fittings located on the roof surface effectively drain water into heavy showers excluding roof flooding. Their location and quantity must be determined taking into account the design rules for these structures and construction requirements for the design of drains and sewerage systems for buildings. The required number of funnels on the roof depends on its operating conditions, architecture and amount of precipitation. The funnel comes with a special filter that protects the drain from foreign objects getting into it. To prevent the water in the drain from freezing, the mouths of the funnels are equipped with special thermal cables, which guarantees rapid drainage of water at any time of the year.
External drainage is more often used as drainage from a flat roof in private houses, because the internal one is more suitable for installing flat roofs of large industrial buildings. External drainage is usually performed using overflow windows, which are installed in the parapet along with roof storm drains. Ideally, self-regulating thermal cables should be used in this case, since the storm inlet and overflow window, by virtue of their design, winter period susceptible to icing.
When choosing a drainage system, due attention should be paid to the choice of structural material. For example, products made of PVC (polyvinyl chloride) are less susceptible to icing than metal ones.
Flat roof design
The flat roof design is a simple and very profitable option for home improvement. It is easy to maintain and opens up a lot of new possibilities.
Design and installation of a typical flat roof: a thorough overview of technological details
The apparent simplicity of a flat roof often misleads novice home builders. The elementary configuration suggests efficiency and low cost of construction. The minimum number of structural elements can dull the vigilance of independent performers who are ignorant of the intricacies of the roofing business. In reality, installing a flat roof requires scrupulous adherence to the rules unique to it, guaranteeing the flawless operation of the structure and long-term operation.
Specifics of flat roofs
Flat roofs are a separate category of roofing structures that do not require the construction of a rafter frame. Purely visually, it is a ceiling that rests directly on the walls of the building. Due to the absence of slopes, a flat roof does not upset the windage that occurs under the influence of gusty winds. However, its configuration does not contribute to the rapid removal of snow deposits from the surface.
The load from the snow is not transferred to the rafters, as in standard pitched systems, but presses directly on the walls of the building. Therefore, it is strongly recommended to equip houses with flat roofs in regions with insignificant amounts of winter precipitation and high wind loads.
In regions and districts of the country located in the middle zone and to the north, flat roofs are used mainly in industrial construction. Private owners install them over one-story extensions, garages, and household buildings. For an independent craftsman, a flat roof over a shed or shed is an excellent option to practice as a roofer.
Briefly about the design of a flat roof
It is customary to call roofs flat, the only conditional slope of which is located to the horizon at an angle from 0º to 1.5º, or otherwise up to 2.5%. However, a number of technical sources call systems with a slope of up to 5º flat, a percentage value of up to 8.7%. Even roof structures have a slight slope, creating a clearly horizontal impression. It is formed to drain wastewater to drainage points or to an overhang.
Regardless of the steepness, the layers of a flat roof are arranged in a strictly defined order:
- Vapor barrier covering the base. It is necessary to protect the insulation from the penetration of household fumes.
- Insulation laid in one or two tiers. Required to prevent leakage of heat waves through the upper ceiling, used exclusively in insulated systems.
- A screed created when the thermal insulation is insufficiently rigid or when there are no slopes for drainage.
- Waterproofing that protects the insulation and ceiling from destructive work atmospheric water. It is laid with a continuous waterproofing carpet.
- A finishing coating that gives the structure an aesthetic appearance.
The brands of waterproofing materials currently supplied to the market successfully perform the functions of finishing roofing. These include numerous rolled and mastic bitumen, bitumen-polymer, and polymer varieties. Most of them are laid in one layer.
Due to the slight slope of flat roofs, the use of piece materials in the arrangement is contraindicated, because multiple joints between elements create the risk of leaks. It is undesirable to use large sheet metal due to the harmful effects on the material of water stagnating on a flat surface during periods of heavy rain and snowmelt.
When using old, well-known roofing felt types of roll coverings, the finishing roof is arranged in 4 or more layers, the lower of which plays the role of waterproofing. A mastic or emulsion self-leveling roof is constructed in a similar way: the emulsion or mastic is applied in five or more layers, alternating pasty or creamy material with layers of fiberglass or polyester.
To lay and fix the above elements of the roofing pie of a flat roof, a rafter structure is not required. They are laid directly on the base, which can be a ceiling, a screed created on top of it, or the upper plane of the attic structure. For fastening systems with PVC coated use the adhesive, mechanical or ballast method. Self-leveling roofs are applied according to their name, the descendants of roofing material are fused or glued.
Unlike pitched counterparts, flat systems do not have sheathing that creates ventilation ducts for washing the insulation with air currents. Therefore, the selection of design solutions, materials and their sealed installation should be approached with due respect and focused attention. A ventilated flat roof is only possible when lumber is used in the construction of the ceiling and attic. The latter option is most often used in private construction.
Types of floors used
The construction of flat roofs is carried out on floors made of reinforced concrete, wood and profiled sheets. The choice of material for the ceiling depends on the purpose of the roof structure, the size of the span to be covered, possible operation and ease of maintenance.
One of the significant advantages of a flat roof is the possibility of organizing a used area on it: a place for relaxation, a solarium, a green area, a terrace, etc. Of course, the overlap for such objects should be quite powerful. In addition, in the flat family there are roofs that do not involve incidental use, and therefore do not require a thorough covering.
Depending on the operational criteria, flat roofs are equipped with:
- Reinforced concrete floors, if it is planned to organize useful space above a long-span brick or concrete box.
- Steel profiled flooring on metal beams, if an unused roof is being constructed that covers spans of any size between walls made of brick or other artificial stone.
- Wood panel made from boards 40-50mm thick, up to 180mm wide. It is used to cover medium and large spans of wooden buildings in the event of planned operation.
- Particle boards and fibreboards on wooden beams, used to cover small spans of wooden and stone buildings. They are used if an unused roof is being constructed.
Lumber is a leader in the construction of low-rise residential buildings, because... are ahead of concrete and steel competitors in terms of environmental criteria. Note that wood is inferior in fire resistance. True, fire hazards in low-rise housing construction are not recognized decisive factor. In addition, there are effective means to combat it - fire retardants.
Rolled coverings in flat systems with a wooden base then serve only as waterproofing, on top of which plank or parquet flooring is installed. If a flat roof is being erected over a brick or concrete box, it is wiser to lay a reinforced concrete floor for the object in use or corrugated sheet for the one not in use.
The overlap of a flat roof does not always serve as the basis for its installation. In some cases, an attic structure is erected above the ceiling, which can be either a canopy over the base with a roofing pie, or the base itself. The structure of the roofing pie of attic roofs is similar, but the layers can be located at different levels.
With or without an attic?
The unconditional inclusion of flat roofs in the category of non-attic structures is fundamentally incorrect, although it has strong technical justifications. They may or may not have attics, although they are not formed by installing rafter legs.
Depending on the presence of an attic, flat roofing systems are divided into:
- Without roofs, the elements of which are structurally combined with the ceiling. They are completely devoid of an attic superstructure, which significantly reduces the budget allocated for their construction.
- Attics with an attic superstructure above the ceiling. The minimum height of the superstructure is 80cm. The construction of attic structures for flat roofs is more expensive, but by separating the floor from the roof, the service life of the system increases at least three times.
In addition to the budget cost, one of the advantages of atticless systems is the ability to eliminate mechanical cleaning. The snow will melt due to the heat emanating from the room. Due to spontaneous precipitation, it is not advisable to equip flat roofs without an attic with parapets. It is enough to install railings, which further reduces costs. The disadvantage of the absence of an attic will affect when identifying the causes of leaks, because the condition of the thermal insulation and other layers of the cake cannot be controlled.
The attic is air chamber between the ceiling and the roof. This is a kind of buffer that compensates for the difference in temperatures outside and inside the premises. The presence of an attic reduces the likelihood of condensation formation, and as a result extends the life cycle of structural elements. Elements of the attic system are always available for observation: the simplicity of inspections is difficult to overestimate.
An undeniable advantage is the possibility of installing insulation after construction, which prevents it from getting wet. The disadvantage of flat roofs with attics is their high cost and the need to regularly clear snow.
Despite the mythical cheapness of atticless systems, this is a very complex structure that requires experience from the builder, careful selection of materials and adherence to technologies for their hermetic connection. It is better for an independent craftsman to give preference to roofs with an attic, if their construction is not excluded by the design decision.
Subtleties of water drainage
Flat roofs must be equipped with drainage systems that all year round are obliged to freely drain water at an operational pace. Systems come in external and internal types.
The optimal type of drainage system is determined by the climatic conditions of the construction area:
- External drains are constructed when constructing flat roofs in the southern regions, where icing of drains in external pipes is excluded. According to the external type, water is discharged to pipes located outside along the perimeter of the building or to a gutter attached along the lowest overhang. In the middle zone, only flat roofs of non-residential buildings are equipped with external systems.
- Internal drainage systems for atmospheric water when installing flat roofs are built in the middle zone and to the north. In accordance with internal circuit water on slopes or obliquely installed pipes transported to water intake points in the center of the roofs. Drainpipes transporting water to the sewer system are laid inside the building, but isolated from the premises.
Despite the impressive cost, the construction of an internal drainage is mandatory for temperate and northern latitudes, and in the south its construction is irrational.
Installation of slopes for drainage
If the slope of the flat roof was not provided for during construction old roof and the construction of a new one, it must be created. The roof must be inclined towards the water intake funnels by at least 1-2%, approximately 1º. Those who want to know how to correctly make a slope on a flat roof and what material is best to use to form slopes should adhere to the following recommendations:
- Slopes on reinforced concrete slabs are made mainly using a screed, or a screed is combined with preliminary filling of expanded clay or laying slab insulation. On an unused roof, it is enough to lay wedge-shaped mineral wool slabs, produced specifically for forming slopes.
- Slopes on corrugated floorings are formed using metal structures or wedge-shaped insulation.
- Slopes on wooden bases are specified constructively, but if they are not included in the project, it is possible to use wedge-shaped mineral wool.
Due to their serious weight, screeds are poured only for exploited roofs erected above concrete floor. On a concrete slope, the recommended thickness of the screed is 10-15mm, on rigid insulation panels 15-25mm. For backfill thermal insulation, the screed is poured with a layer of 25-40 mm and a metal mesh is used for reinforcement.
Nuances of organizing ventilation
Normal ventilation can be done in the only way - by installing battens on the floor beams; similar methods are dictated to us by the construction schemes of pitched structures. It is clear that the above method is only valid for wooden options, but for roofs on a concrete base or corrugated sheet it is unacceptable.
The ventilation system for roofing pies on concrete and corrugated sheets depends on the type and characteristics of the finishing coating. PVC roofing is capable of spontaneously transmitting excess moisture from the insulation to the outside, so there is no need to install ventilation ducts between it and the insulation.
When using bituminous and bituminous polymer materials It is mandatory to install wind vanes over the entire area of the flat roof. The spacing of these devices depends on the thickness of the insulation. Vane aerators ensure the removal of moisture from the under-roof space to the outside.
Algorithm for constructing a flat roof
Let's consider the common case of constructing an unused flat roof over an extension on suburban area. It will be equipped with an external drain. Insulation of the structure is not expected, because climatic conditions and the purpose of the room below do not require thermal insulation.
The sequence of constructing a cold flat roof on wooden beams:
- We mark the installation step of the floor beams, for which we will use a board 40-50mm thick. Installation step from 50 to 70cm: choose it based on the actual length of the walls. There should be equal spaces between the beams.
- We place the board on its edge, fasten it with nails or corners. The required slope to the lowest overhang is created spontaneously due to the difference in the height of the box walls.
- We lay a continuous flooring of OSB boards on the beams, moisture resistant plywood or other similar material. There should be a gap of 3-5mm between the plates to compensate for thermal expansion. They are fastened with galvanized self-tapping screws or rough nails.
- We install along the perimeter of the roof wind board, the edge of which rises 5-7 cm above the plane of the future roof so that a small side is formed.
- We nail it to the sides wooden slats with a triangular section or a regular plinth. These are fillets necessary to drain water from the edges of the roof.
- We treat all wooden elements with antiseptics and fire retardants. After they dry, apply primer.
- We lay an additional waterproofing carpet in a strip along the perimeter on top of the fillets. In the case of junctions and pipes passing through the roof, additional waterproofing is applied to the adjacent vertical planes similarly, i.e. on top of the fillets.
- We fuse the finishing roofing material selected for installation, heating its back side with a gas burner.
In the case of thermal insulation, a vapor barrier layer is first laid out on the base, the edges of which are placed on the vertical sides. Insulation boards are placed in a kind of pallet formed by the vapor barrier, the thickness of which is calculated in accordance with the requirements of SNiP 02/23/2003. Thermal insulation is attached to the base with self-tapping screws and telescopic devices.
Then waterproofing is laid over the sides and junctions. If one of the latest brands of rolled waterproofing material is chosen for the installation, then it will also be entrusted with the responsibility of the finishing coating.
An impressive range of new polymer-bitumen and polymer coatings laid in one layer, which helps to save the installer’s effort and construction costs. Among them there are materials that are extremely preferable for home craftsmen and do not require the use of a gas burner. They are glued onto mastics or using the back adhesive side and fixed mechanically, laid loosely and loaded with ballast.
Video for DIYers
A video collection will help you consolidate information about the difficult task of constructing flat roofs:
We hope that the information we presented will help future roofers who decide to practice with their own hands in constructing a not-so-simple design.
There are many conditions for the proper construction of a flat roof, but they must be observed for ideal operation and long service. Information about the intricacies and specifics of constructing a flat roof will help not only determined craftsmen, but also owners of country estates who resort to the services of third-party construction organizations.
Some of the materials for writing this article were taken from here:
But for me, a flat roof is the best option, it is preferable to use a roof slab made of expanded clay concrete grade 100, and also do not forget about thermal and waterproofing. Still, a flat roof is more aesthetically pleasing to me. And the fact that in winter you will need to constantly remove snow, I think that this must be done from any other roof too. But if you consider that the material is concrete and plus protection, then when performing this necessary measure there is no risk of structural damage.
Flat, but still with an insignificant slope of a couple of degrees, or rather. A flat roof to some extent makes it possible to minimize costs. Flat roofing is utilitarian. Temperature insulation and water protection are also excellent. The use of rolled materials creates the possibility of savings, ease and speed of installation, and a good degree of protection from weather conditions.
Installation of a flat roof: design, device, installation, layers, elements
The installation of a flat roof requires strict adherence to the rules for installing elements and a clear arrangement of layers laid when installing rafter-less structures
Flat roofs are in demand in modular construction. Among the advantages of this method are the affordable cost and high speed of construction of housing, as well as the possibility of gradually increasing its area
Architects and developers are attracted to these unusual buildings, where you can equip an observation deck or even set up a real hanging garden. Of course, in practice everything turns out to be more complicated than in theory.
Designing a flat roof raises many questions regarding its cost, choice of materials for insulation and waterproofing, organization of water flow, maintenance, etc. Finding answers to them is not so easy. The fact is that domestic contracting companies working in the field of cottage and rooftops are well familiar with the most popular design - pitched, but, as a rule, they have no experience in constructing flat roofs, which are designed completely differently.
Flat roof cost
What immediately attracts attention is the fact that the area of a flat roof is smaller than a pitched roof, which means that less materials will be required, and the work will be cheaper. However, this statement is only true for regions with a warm climate and low snow load, especially if we are talking about an unused roof. In central Russia, to ensure the reliability and durability of a horizontal roof, it is necessary to apply rather expensive engineering solutions.
Beam floor
In principle, when constructing a floor, you can use a combination of beams (wooden, steel) and load-bearing corrugated sheeting. However, experts do not recommend using wooden beams (with the exception of those made of LVL beams with a cross-section of 200 × 100 mm) in regions where the snow pressure exceeds 1.2 kPa (about 120 kgf/m2) - that is, in most of the territory of the Russian Federation. A roof covering made of steel I-beams and corrugated sheets with a wave height of 60 mm and a wall thickness of 0.7 mm allows you to cover a span of up to 12 m and can withstand a pressure of at least 6 kPa. But in general, it is less durable than concrete, and is relatively rarely used in individual construction. It makes more sense to use corrugated sheeting as permanent formwork, which, by the way, does not replace the need to build a reinforcement frame.
It turns out that 1 m2 of a flat concrete or steel base, the load-bearing capacity of which will allow it to withstand the weight of snow cover, costs 2–2.5 times more than a wooden beam structure of a pitched roof. The difference in the volumetric consumption of insulation is leveled due to the fact that a flat roof requires more expensive high-density material. There is still hope to save on roofing, but modern polymer membranes - the optimal waterproofing for horizontal roofs - are no cheaper (and sometimes much more expensive) than flexible tiles. There is no need to install snow guards, but you cannot do without a roof hatch and a drainage system. If you try to cut costs according to the estimate, you will subsequently have to pay the price of having to repair the roof every 10–15 years.
The durability of a flat roof largely depends on the ability of the load-bearing base to withstand operational loads without significant deformation
Finally, it should be taken into account that flat roofs are appropriate only on houses of modern architecture - with a large glazing area and complex finishing with the latest facade materials. Both will not be cheap at all.
On a solid foundation
As a rule, in low-rise housing construction, the flat roofing is a prefabricated or monolithic reinforced concrete slab. Reinforced concrete slabs (PB, hollow PC, PV, etc.) are capable of covering a span of up to 9 m in length and can withstand a pressure of 8, 9 or 12.5 kPa (this value is indicated by the last digit in the product labeling). They can serve as a “base” for any roofing pies, including those with a top layer of paving slabs or fertile soil. However, to install the structure, it will be necessary to ensure that a truck crane can enter the site (while steel beams and flooring can be easily lifted using winches). The depth of support of the ceiling on the wall depends on the material of the latter - for example, for brick this parameter should be equal to the thickness of the slab. Before proceeding with the installation of the roof, it is important to seal the joints of the elements with mortar and additionally seal them with elastic polymer tape.
The main advantage of membranes based on artificial rubber is that they retain elasticity at low temperatures, that is, they can be installed in winter
Classification of flat roofs
Flat roofs are divided into unused and used. The former visit only for inspection, prevention and repair; For this purpose, a roof hatch is installed, to which an attic ladder leads. The roof in use in cottages most often serves as a terrace, that is, a durable wear-resistant coating must be laid on it, and the load-bearing base is designed for increased loads. A type of exploitation is a roof with landscaping, laid with a turf layer on top of the main heat-waterproofing pie; Usually there are paths and a recreation area on it. A convenient exit to the roof in use should be provided, for example from a vestibule superstructure.
A monolithic reinforced concrete floor is erected from heavy concrete using removable (for example, from OSB boards on jack stands) or permanent (from corrugated sheeting) formwork. It is reinforced with a two- or four-level welded frame made of rods with a diameter of 12 mm. The dimensions of a monolithic slab are not regulated (unlike a prefabricated one), which provides the architect with freedom when designing a building; other advantages are the absence of seams, the comparative simplicity of the installation of passage units (chimney, ventilation ducts) and high load-bearing capacity (subject to compliance with technological regulations).
Roof protection from cold and heat
In the low-rise sector, mostly flat roofs without attics are in demand, because the attic requires additional costs and disrupts the architectural proportions of the house. This means that the roof must protect against winter cold and summer heat. A common feature of flat roofs is that the heat-insulating layer is located on top of the supporting structure (in pitched roofs it is usually located between the rafters). If you insulate the room from below, the dew point may shift into the thickness of the ceiling, which will lead to a reduction in the service life of the latter.
Mastics should be used primarily on roofs of complex configurations
As for roofing options, there are dozens of them. Suffice it to say that more than 40 “recipes” are given in SP 17.13330.2011 alone. At the same time, companies producing coatings and insulation materials are offering more and more new engineering solutions. However, they are always based on one of two fundamental schemes - traditional or inversion.
TechnoNIKOL roof installation diagrams
“TN-ROOF Terrace”: 1 - ceiling; 2 - vapor barrier; 3–5 - EPPS (including the slope-forming layer); 6 - fiberglass; 7 - LOGICROOF V-GR membrane; 8 - geotextile; 9 - tiles on supports
The traditional design in general terms is as follows: a vapor barrier film (polypropylene, polyethylene, butumen-polymer) is laid on top of the load-bearing base, followed by insulation, for example, mineral wool slabs, which have a compressive strength at a ten percent deformation of at least 30 kPa, one or two layer with a total thickness of 200 mm. Above is a separating layer (for example, made of polyethylene film), along which a reinforced slope-forming screed is poured (a flat roof must be given a slope of 2-3% towards the center or edges to ensure water drainage). The dried screed serves as the basis for a roll or mastic waterproofing coating.
“TN-ROOF Green”: 1 - overlap; 2 - ramp made of expanded clay; 3 - reinforced screed; 4 - bitumen primer; 5 - “Technoelast EPP”; 6 - “Technoelast Green”; 7 - geotextile; 8 - EPPS; 9 - PLANTER GEO membrane; 10 - fertile layer
Other options are also possible. For example, a slope-forming screed can be located at the very bottom of the pie; in this case, the roof waterproofing is fixed with gravel ballast, paving slabs on supports or special dowels. Some materials, say the “RUF SLOPE” system (Rockwool) or “TechnoNIKOL Slope”, allow you to do without a screed altogether: the slabs have variable thickness, and with their help it is not difficult to create smooth changes in level to ensure water drainage.
An inversion roof is designed differently: in it, insulation resistant to constant exposure to water (usually extruded polystyrene foam - EPS) is placed on top of the waterproofing. At the same time, the latter is reliably protected from mechanical damage and is located in the positive temperature zone (freezing-thawing cycles are destructive for almost any material). It is easy to turn an inversion roof into a usable one, for example, by covering the insulation with a drainage layer of sand and gravel and laying paving slabs. The disadvantages of the design include more complex drainage. However, we need to talk about gutters separately.
There are special requirements for thermal insulation for flat roofs. The material must not only have a low thermal conductivity coefficient, but also have good resistance to mechanical loads - both distributed (pressure from the overlying layers of the roofing pie, equipment, snow) and local ones that arise during installation. In addition, it is important that the material has hydrophobic properties and is non-flammable. At the moment, there are several ways to install thermal insulation: using mechanical fasteners, adhesive and free laying. In addition to traditional two-layer insulation, single-layer installation is becoming an increasingly popular solution. Rockwool offers unique dual-density slabs that consist of a rigid top layer and a lightweight bottom layer, which speeds up work and improves its quality.
Grigory Gromakov
Specialist in development of the “Flat roofing” direction of the ROCKWOOL company
Water drainage on a flat roof
The flat roof is equipped with a parapet (attic) 30–90 cm high, which helps ensure an organized roof; on a roof in use it also serves as a safety fence. At the same time, the design of gutters should be approached very responsibly, because in case of an error, a huge puddle can form above your head, which can also lead to damage to supporting structures.
As a rule, the choice is made in favor of an internal drain. Such a system is less exposed to the atmosphere and is therefore more durable and reliable than an external one. Let's talk in more detail about its main elements.
Water intake funnels are installed on low areas of the roof. As a rule, on roofs with an area of up to 150 m2, two funnels are installed - the main one, connected to the riser, and the emergency one - with water discharged through a hole in the parapet. With an increase in the number of funnels and risers, the reliability of the system increases, but its cost also increases.
For inversion and green roofs, special funnels with drainage rings have been developed to collect moisture from the intermediate layers. Water receivers must be equipped with electric heating based on a self-regulating cable - then they will properly perform their function during alternating thaws and frosts.
Traditional covering with external drainage 1 - ceiling; 2 - slope-forming screed; 3 - vapor barrier; 4, 5 - mineral wool insulation; 6 - waterproofing; 7 - drain
In a new type of system, the so-called siphon-vacuum system, special funnels are used to prevent air from being sucked into the water flow. Thanks to them, the speed of fluid movement in the pipe (and hence the throughput of the latter) increases, which makes it possible to reduce the diameter of the system elements. However, for low-rise buildings, the savings turn out to be insignificant; moreover, such systems require more accurate calculations than gravity systems.
The drainpipe is made from sewer pipes - polypropylene, polyvinyl chloride, and it makes sense to use sound-absorbing products, for example RAUPIANO Plus (REHAU), or soundproof the riser, otherwise you will hear the murmur of water for hours. The riser is connected to the funnel using an elastic coupling. When laying pipes, the number of bends and the length of horizontal sections, which reduce the throughput of the system, should be minimized.
A drainage pipe laid in the basement or insulated underground connects the riser to the rainwater drainage system or ensures the discharge of water into a linear drainage tray. In the second case, there is a risk of clogging the outlet with ice, so the riser should be equipped with a “winter” outlet to the domestic sewer (the latter should be equipped with a water seal). The outlet pipe is cleaned through a collapsible connection or an inspection module.
Drawing: Vladimir Grigoriev/Burda Media
Inversion roof covering with internal drainage 1 - screed; 2 - PVC membrane; 3 - EPPS; 4 - funnel with drainage ring; 5 - drainage membrane; 6 - sand; 7 - paving slabs
When choosing the standard size of elements of a traditional gravity system, they proceed from the intensity of rain in a given area, focusing on SP 32.13330.2012.
The external drainage system is more vulnerable than the internal one, and also affects the appearance of the facades, but it does not require holes in the roof and ceilings and does not eat up the usable area of the house. Water is discharged through parapet funnels or pipes embedded in the parapet, under which classic funnels (like on a pitched roof) and down pipes attached to the walls with brackets are installed. When calculating, it is assumed that for every square meter of roof area there should be 1–1.5 cm2 of the cross-section of drainpipes. Elements of the external system can be made of PVC, steel, copper, zinc-titanium.
For roofs in use, as well as roofs installed in regions with harsh climatic conditions, the inversion scheme is ideal. Since the waterproofing layer is located under the thermal insulation layer, it is protected from mechanical influences, as well as from temperature changes and UV radiation, which significantly extends the service life of the roofing system. Waterproofing materials based on modified bitumen must be laid in at least two layers - this technology is more common, and in addition, it allows you to level out possible errors when fusing the material. One layer is enough for a polymer membrane, and reliability is ensured by automatic welding equipment, which greatly increases the speed of work. In addition, when installing a polymer membrane, an open flame is not used, so the technology is considered safer.
Dmitry Mikhailidi
Head of the Engineering and Technical Center of the Technical Directorate of the TechnoNIKOL Corporation
Roof landscaping
Since ancient times, turf-covered roofs have been used in countries with moderately cold and humid climates, and the green carpet performed the main moisture-protective function in them.
As part of the modern concept of a green roof, a layer of fertile soil with plants is needed to give unusual features to the appearance of the building, decorate the terrace roof and extend the life of the coating by protecting it from ultraviolet rays. In addition, it absorbs rainwater, unloading gutters, dampens the sound of rain, protects the upper floor rooms from overheating in the summer and reduces heat loss in the winter. It is believed that landscaping almost doubles the life of a roof. Its disadvantages include an increase in loads on the supporting structures of the building and an increase in construction costs. In addition, a green carpet needs care, the intensity of which depends on the selected plant species. If you do not pay due attention to the plants, they will freeze and die from drought.
To green the roof, you should lay on top of the main waterproofing layer (in an inversion scheme - on top of the insulation) an additional cake made of materials that will ensure protection of the waterproofing layer from roots, filtration and drainage of rainwater. For these purposes, special films, dense geotextiles, gravel bedding or drainage and moisture storage membranes made of high-density polyethylene, for example PLANTER GEO or Delta-Floraxx, are used.
Then a mixture of minerals and fertilizers is poured - the so-called soil substrate. You can prepare it yourself by adding fine expanded clay (5–15%), sand (about 20%) and fertilizers to a light soil mixture of neutral peat. As for plants, the easiest way is to limit yourself to meadow forbs and drought-resistant ground covers - sedum, herbaceous carnation, thyme. They do not need to organize an irrigation system, and the thickness of the soil layer can be only 6–12 cm (this type of roof is called extensive). If you plan to walk along the roof among ornamental shrubs, you will have to provide watering and increase the soil thickness to 20–40 cm. Such a roof is called intensive; it creates a significant additional load on the floor, so it must be provided for at the design stage of the building.
The terrace design provides convenient communication between the living quarters of the cottage and the exploited roof, which serves as a resting place
Rolled materials based on modified bitumen, as a rule, are fused with a gas burner, but it is difficult to prevent small flaws that can cause leakage (if there is no second layer)
Rolled PVC membranes , for example, Sikaplan WP, Logicroof, Ecoplast are strong and durable (up to 30 years without repair) and do not support combustion. However, they require a professional approach to installation (the joints of the strips must be carefully welded with hot air) and are relatively expensive - from 320 rubles. for 1 m2. It is important to consider that this material does not tolerate contact with bitumen.
Rolled membranes made of ethylene-propylene rubber (EPDM) and thermoplastic polyolefins (TPO) , for example Firestone RubberGard, Logicroof P-RP, retain elasticity at low temperatures. Note that EPDM membranes are highly flammable (class G4) and are designed mainly for use in the construction of an in-use roof, where the waterproofing is covered with tiles, gravel or soil. EPDM and TPO membranes cost 1.3–1.5 times more than polyvinyl chloride membranes (mostly imported products).
Polymer-bitumen mastics They allow you to create a seamless coating, but they can only be applied to a durable, non-cracking base - a floor slab or a carefully reinforced screed, and this process is quite long and labor-intensive. The service life of a two-layer coating with a thickness of 5 mm is about 20 years, the price is from 120 rubles. for 1 m2. In practice, mastics are used mainly for roof repairs and gluing rolled materials.
Polymer and cement-polymer self-leveling waterproofing
, say Aquascud, Osmolastic, Osmoflex, is highly elastic
and UV resistance. To improve performance, materials are used in combination with special primers and lining films, and reinforced with mineral fiber (all components are supplied as a single system). The estimated service life of the coating is more than 50 years; price - from 700 rub. for 1 m2.
Flat roof: a pragmatist's view
| Advantages | Flaws |
|---|---|
| Eliminates snow avalanches and reduces the risk of falling ice. | Requires significant costs to construct a foundation with high load-bearing capacity. |
| Provides convenient access to chimneys, ventilation risers, antennas; Compared to pitched ones, it is easier to maintain and repair. | It is more susceptible to atmospheric factors than pitched, so durability is guaranteed only if expensive materials are used. |
| Can serve as a recreation area or terrace. | Requires increased attention to the arrangement and condition of the drainage system (especially with internal drainage). |
| Slightly less susceptible to wind loads than pitched. | |
| Allows you to implement the principle of phased modular construction (to make an extension to the house with pitched roof, we need to solve a difficult architectural and design problem). |
A flat roof in a private house provides many different possibilities. With such a simple design you can save on roofing materials and works, and installation is carried out in a shorter period of time. It is also easier to place various systems on its surface: antennas, hoods, solar panels and others. In addition to all this, additional space can be used by arranging a garden, recreation area or greenhouse on it.
However, despite the cheaper installation, many nuances must be taken into account so that such a roof does not become a “headache” for the home owner.
Flat roof design
A flat roof, like any other, must fully perform all its functions: protection from water and its drainage and thermal insulation. In addition, it must have sufficient strength to withstand external loads.
This is what determines the structure of the roofing pie, which consists of the following mandatory elements.
- Base. This part bears all the main loads. The ceiling must be very durable, but it all depends on whether the roof will be used or not. Most often, the base is a reinforced concrete slab laid on load-bearing walls, less often on non-residential buildings - a layer of profiled sheets.
- Vapor barrier layer. Performs a protective function, which consists in preserving materials from steam penetrating from inside the room.
- Thermal insulation. Reduces heat consumption from the house.
- Waterproofing. A flat roof does not drain away all the water completely, like gable roofs; as a result, high-quality protection is needed from the penetration of room moisture.
For normal moisture removal, a slope is used. Most often, this is a screed that forms angles of inclination along which water can flow into a prepared system of trays for its removal from the roof plane.
Saving on any parts of a flat roof is unacceptable, otherwise it will lead to leaks, freezing and other negative phenomena of a poorly installed roof pie.
Types of Flat Roofs
The presence, order and sequence of individual elements of the roofing pie determine the type of roof. The following types of flat floor structures are distinguished:
- Unexploited. These designs can be seen at multi-storey buildings. It is believed that their surface is not intended for use and is designed for short-term stay of people. In this option, on non-residential buildings you can use a profiled sheet as a base.
- Exploited. In this case, it is necessary to have a concrete base capable of withstanding heavy loads. The surfaces can be used as a garden, recreation area or even car parking. In addition to a solid base, it is important to observe the angle of inclination, which should not exceed 3 degrees.
- Inversion. The design involves changing the order of layers of the cake. The waterproofing is placed under the insulation, which allows it to be protected from damage. Quite often this type of roofing is used in the construction of private residential buildings.
- Ventilated. These types of roofing have a ventilation system (built-in aerators) that evaporate excess moisture from the thickness of the roofing cake. Can be combined with other types of roofs.
In addition, the type of roof depends on other factors, for example, whether the room is heated or not.
Installation of a flat roof on different types of buildings
Depending on whether the room will have a heating system or not, the technology for assembling the roof may differ during installation.
Roofs on unheated premises
Typically, unheated buildings are garages, sheds, gazebos, and various pavilions.
- The required slope of 3 degrees on such buildings is formed by the load-bearing roof beams. The height difference is about 30 millimeters per 1 meter of beam length.
- After laying the beams, a flooring is made that will serve as a base. These can be boards or profiled sheets. They are secured with self-tapping screws or other suitable fasteners.
- If the room is unheated, you may miss a layer such as thermal insulation. Waterproofing material is laid on the base. Roofing felt is used as a waterproof coating. It is spread in overlapping strips (about 150 mm) and additionally fixed with slats, which are placed along the slope of the roof.
This is the simplest version of a flat roof that can be mounted on a utility room. unheated room do it yourself with minimal investment of money and time.
Assembling a flat roof on heated buildings
IN residential buildings With a heating system, the roofing pie of a flat roof will be different. Here you will definitely need a thermal insulation layer, high-quality hydro- and vapor barrier. The presence of the latter is no less important, since water vapor can gradually ruin the entire roofing pie.
- The floor under the base is assembled from wooden beams, which are placed every 900-1000 mm.
- They are covered with flooring made of boards with a cross-section of 40-50 millimeters. The thickness of the lumber is selected depending on the distance between the beams. The larger it is, the thicker the boards are needed.
- Roofing felt is laid on the flooring, it is cut and straightened in advance. Waterproofing sheets are laid with an overlap of about 100-150 mm.
- The thermal insulation layer can be made using the bulk method. To do this, fill the resulting base with a layer of expanded clay up to 300 mm and level it.
- Next, pour onto the layer of thermal insulation backfill cement-sand screed(minimum thickness 30 mm).
- After the cement has hardened, the surface is covered with bitumen-based soil and covered with a layer of roofing material.
You can also install a more solid roof made of monolithic concrete.
Monolithic concrete flat roof
In this option, you make a durable concrete base with your own hands.
- An I-beam is used as support beams, which are laid level without forming a slope.
- For pouring, you will need to prepare concrete of a grade not lower than M250; it is prepared in a concrete mixer, maintaining a ratio of 4:1.5:1:1, where the ingredients are crushed stone (20-25mm), cement (m400), water and sand, respectively.
- For pouring, a base is made of boards, which are mounted on the lower flanges of I-beams and covered with roofing felt.
- Fine crushed stone is poured on top of the waterproofing, which is filled with the resulting concrete. The filling must be done at one time, otherwise the structure of the roof will not be the same.
- Next, expanded clay is poured in and a slope is made.
Leaning
Sloping is the formation of slight slopes on the surface of a flat roof, which allows water to be removed from its surface. The drainage system is assembled in two versions: external and internal. That is, the trays can be attached to the end of the roof or on its surface.
If the drainage gutters are located internally, the presence of drainage basins is planned in advance, the number of which is calculated as follows - 1 funnel per 25 square meters of roof area.
