For a user uninitiated in capital construction, it is unlikely that it will be known what a Mauerlat is, what role it plays in building a structure, and so on. Therefore, the question of how the Mauerlat is attached to aerated concrete is generally misunderstood.

However, the use of such technology is a relevant and very effective solution. With it, you can solve a number of significant problems that can reduce the durability and strength of the structure.

It is also necessary to mention a more economical variant of the implementation of the specified method of fastening. If it is necessary to fasten the Mauerlat to aerated concrete without an armored belt, then in this case it is not a continuous armored belt that is poured, but concrete pillows are made in the right places. Such a mount for foam blocks is also quite reliable.

2.3 Metal studs

In the presence of a small house, as well as a slight pressure of the roof, a lightweight method can be used to fasten the walls of the cinder block with the Mauerlat beam - metal studs embedded in the wall. These are steel fasteners in the form of bolts with a base in the form of a square with sides of more than 5 cm.

If, when laying a cinder block, studs are embedded in the wall, they must be installed one or two rows to the top edge. The length of the stud should be sufficient to pass through the beam.

Subsequent fixation similar to fastening a mauerlat with a cinder block using anchor bolts.

2.4 Waterproofing during installation

Having decided on the method of fastening, it is necessary to calculate the fasteners and their location. If it is necessary to fix the Mauerlat to the gas block without an armored belt, then the first option is suitable - steel wire.

When arranging a pitched roof, the installation of the truss system cannot be performed directly on the walls of the building. An additional element that receives loads from the rafters and transfers them to the walls will be the Mauerlat. Usually this is a special beam that is laid along the perimeter of the walls. Since it takes a serious load from the roof, it is very important to securely fix the Mauerlat on the wall. In the case of brick or concrete walls, everything is simple and clear. But how is the Mauerlat fastened to aerated concrete without an armored belt, because the gas block itself is rather loose and porous, therefore it cannot provide a strong fixation of the fastener? This is what we will talk about in our article.

The functional purpose of the Mauerlat

Usually, the same material is used for the manufacture of the Mauerlat as for the truss system. Most often it is made from a wooden beam. However, if the truss system is made of metal, then this structural part can be made of a channel or an I-beam.

Usually this element is made of the following materials:

• Wooden beam with a section of 100x100 mm, 150x150 mm or 200x300 mm. The beam is made of hardwood and undergoes mandatory antiseptic treatment. The product is laid around the perimeter on the walls of the structure. Joints are fixed with nails or a direct lock. In private construction, a wooden roof structure is most often used.
• Less commonly, rolled profiles are used for these purposes - a channel with a U-shaped section or an I-beam with an H-shaped section. The height of the profile is determined by calculation and can be in the range of 70-120 mm.

A bar or steel beam is attached to the walls. In this case, different methods of fastening can be used. Further, the rafter legs rest on the Mauerlat. They exert a load on this element, which, in turn, evenly distributing it, transfers it to the walls of the building. In addition, this beam keeps the truss system from moving.

Important: since aerated concrete does not tolerate long-term point loads, gradually collapsing, it is recommended to erect a monolithic reinforced belt on top of the walls before laying the Mauerlat.

However, there are ways to lay this structural element on aerated concrete walls without an armored belt. It is also worth remembering that the upper edge of the Mauerlat should be located at a height of at least 30-50 cm from the floor surface. This will ensure effective ventilation of the under-roof space, as well as facilitate inspection and repair of roof structures.

Mounting methods

Mounting a Mauerlat to aerated concrete is much more difficult than to a brick wall.

Mounting a Mauerlat to aerated concrete is much more difficult than to a brick wall. As a rule, this product is laid at a distance of 50 mm from the outer edge of the wall. The following fasteners can be used to fasten the Mauerlat:

• steel wire;
• anchor fasteners built into the masonry;
• special chemical anchors;
• steel pins.

Important: anchors are used to attach the support beam to the reinforced belt or brick walls.

After installing the timber, the rafter leg is attracted to the wall with the help of a twist made of twisted metal wire with a diameter of 3 mm. To fix the wire below the timber, a steel shorty is mounted 6 cm. Instead, the wire can be fixed to the floor slabs. When installing a complex roof, it is recommended to make sure to carry out a reinforced concrete belt, which will give the building additional rigidity and more evenly distribute the load from the roof onto the walls of the house.

To bind the individual parts of the Mauerlat into a single structure, an oblique cut is used, followed by fastening with nails, screws or bolts. Steel plates and staples are used to reinforce the corner parts of the structure.

Using wire to fasten the beam

If wire is used to fasten the Mauerlat, then this must be taken care of even at the stage of laying the walls. The wire must be laid in the tub of walls when performing the last few rows. At the same time, the following sequence of actions is followed:

1. During the laying of aerated concrete blocks, two or three rows before the end of the laying of the walls, a steel wire with a cross section of 6 mm is laid between the elements, which consists of several thinner wires twisted together.
2. At the same time, the middle part of the fastener is inserted into the masonry. Its ends should protrude from the walls. The length of these ends should be such that the wire can be freely wrapped around the timber to be laid.
3. The number of wires used should be equal to the number of rafters installed.

Fixation with pins

Mounting the Mauerlat to the wall of aerated concrete with studs is allowed when installing light roofs on small houses. The materials used to form the roofing pie should be as light as possible and not transfer significant loads to the rest of the structural parts of the building.

This technique is the best suited in the case when it is not possible to equip the armored belt. In such a situation, the timber itself will act as a reinforcing belt. This method causes rather controversial reviews of experts, but in practice it has proven itself very well, providing high reliability and stability of the roof.

To fix the beam to aerated concrete, you will need the following elements:

• studs marking SRT-12, called "dovetail";
• wooden beam with a section of 20x30 cm (the dimensions of this element depend on the thickness of the outer walls).

We perform the work in the following order:

1. We drill holes in the walls of the gas block in increments of 100-150 cm.
2. We insert the studs into the holes and fix them with cement milk or a non-shrinking mortar.
3. Next, you need to perform waterproofing. To do this, two layers of roofing material are laid on the walls. At the location of the studs in the material, holes must be pierced to ensure its snug fit to the walls. Waterproofing will protect the wooden beam from saturation with moisture and subsequent rot, which can come from the walls.
4. With the same step as the studs were installed, holes of a diameter suitable for the studs are drilled in the Mauerlat.
5. Then the beam is mounted on the studs on top of the waterproofing, washers are installed and tightened with nuts.
6. After mounting the beam, the ends, in which individual fragments of the beam are joined, are pulled together with forged steel brackets.
7. Now you can proceed with the installation of the truss system.

If the studs are mounted in the armored belt, then we work as follows:

1. Before the start of pouring the armored belt, studs are placed in it with a step of no more than 100 cm.
2. They are fastened with a knitting wire to the reinforcing cage of the belt. Plastic ties can be used instead of wire to fix the studs.
3. The accuracy of the installation of the studs horizontally and vertically is checked.
4. Concrete is poured into the formwork of the armored belt.
5. After it hardens, the prepared beam is put on with holes on the protruding ends of the studs and is attracted to the surface with nuts.

chemical anchor

This product is also called liquid dowel, injection mass or glued anchor. In fact, it is an adhesive with high bonding characteristics, which is made on the basis of synthetic polymer resin. Thanks to the chemical anchor, it is possible to firmly fasten the metal rod and the base.

Important: unlike other fasteners, the liquid dowel does not create expansion stress in the material, which is especially dangerous for fragile aerated concrete at the edges of the walls.

Unlike mechanical anchors, the fixation of which is based on the use of friction forces and expansion of the dowel made of polymers, the chemical anchor is fixed due to the fact that the adhesive penetrates into the pores of aerated concrete to a considerable depth and firmly fixes the rod in the wall.

Installation of a chemical anchor is carried out in the following sequence:

1. First, a hole is drilled along the anchor. However, its size should be slightly larger than for a conventional anchor bolt.
2. Using a special brush or compressed air, dust, debris and metal crumbs are removed from the channel.
3. A special chemical adhesive is poured into the hole prepared in the wall.
4. After that, a steel rod is inserted there - a threaded stud M 12-14. Also for these purposes, you can take a piece of reinforcement of a suitable diameter.
5. The adhesive composition gains the required strength in 20 minutes, provided that the ambient temperature is approximately 20°C.
6. After the chemical composition hardens, the rod is securely fixed in the wall. Moreover, the fastening strength is much higher than that of the mechanical method.

Advantages of using a liquid dowel:

• The service life of such fasteners is more than 50 years.
• This method of fixation can be used on the edge of the walls, without fear that it may crack.
• Fasteners have a fairly high chemical resistance.
• Fastening is allowed to be carried out on wet material, that is, installation can be carried out even in rainy weather.
• The work on the installation of the power plate and the arrangement of the roof can be carried out without the use of a reinforced belt, since the chemical anchor is much more firmly fixed in a fragile material than a mechanical dowel.
• This method is ideal for working with aerated concrete.
• The depth of the hole may be less than when installing a mechanical anchor, which must be deepened by 2-3 rows of masonry.

The only drawback of this method of fixation is that welding cannot be performed with a rod attached to a liquid dowel, since the polymer material is destroyed by heating, and the fixation strength is reduced.

Mechanical anchor (anchor bolt)

This is a fairly common way to fix the timber to the walls. The anchor bolt consists of the following parts:

• external spacer;
• internal threaded rod.

Fixation occurs due to the fact that at the moment of screwing the nut onto the rod, the spacer structure is deformed in such a way that it securely fixes the product in the hole drilled in the wall.

Work on the installation of a mechanical anchor is performed in the following order:

1. A prepared beam is laid along the perimeter of the walls.
2. Further, holes are drilled along the entire length of this product for installing anchor bolts. The spacing of the holes is 1 m. It is important to try that the installation sites of the anchors must fall on the corners of the building and the junction of the two ends of the timber.
3. After that, with the help of a drill, holes are drilled in the walls through the holes prepared in the Mauerlat to a depth equal to the length of the anchor. In this case, it is not allowed to make the depth of the anchor less than 2 or even 3 rows of masonry.
4. An anchor bolt is installed in the hole. For these purposes, it is better to take products with a length of at least 50 cm with a thread M 12 or 14.
5. After that, the washer is put on and the nut is screwed tightly. As a result, the steel or plastic dowel is unclenched so that it is firmly pressed into the material and fixes the bolt in the wall.

For the correct installation and installation of the roof truss system, the competent distribution of heavy loads on the building, builders resort to the use of an important element - Mauerlat. Mauerlat is a wooden or metal mount that is fixed at the top of the walls. However, it must be securely fastened.

If builders use metal rafters, then there is a need for an I-beam Mauerlat. It is attached to an aerated concrete wall without an armored belt and performs two functions:

• distributes the loads that are transferred to the walls of the building;
• roof rafters are attached to the metal Mauerlat.

Selection of building materials

In the manufacture of wooden Mauerlat, bars are used. At the same time, experts advise making fasteners from deciduous trees treated with special antiseptic agents. Beams should be laid around the perimeter of the wall. To connect them together, experts install a lock, which must be fixed with nails. This will help to make a solid, solid wood structure. It is important that its size be less than the width of the aerated concrete walls. The beam must be fixed on the inner surface in such a way that a gap of five centimeters remains between the outer cut and the mount. Sometimes builders use brick for a protective belt on the outside of the wall. Before starting installation work, it is necessary to provide waterproofing between the walls and the beams.

Varieties of fastening

There are ways by which you can securely fix the Mauerlat on aerated concrete. It is necessary that the mount is installed as securely as possible - this will help to avoid displacement of the roof. In the construction industry, it is customary to fix an element using the following means:

Waterproofing during installation

Between the Mauerlat and the wall of the building, waterproofing is needed. For this purpose, polyethylene, building materials in rolls or modern waterproofing agents can be used. Such work is extremely important during the construction of a building, otherwise a liquid may condense in the area of ​​\u200b\u200bcontact between materials, which can destroy the Mauerlat. Protection against moisture penetration is the final stage of installation.

The nuances of installation work

Experts believe that it is preferable to install a solid wooden structure around the perimeter of the wall surface. In this case, you need to fasten the wooden bars into a single Mauerlat using a lock. Its dimensions will depend on the characteristics of the bar. After you decide on the type of fastening of the structure to aerated concrete, calculate the location and number of elements, you can begin installation. First of all, workers need to prepare the workplace by insulating the space between the Mauerlat and the concrete masonry. It is important to remember that the areas of contact between wooden beams and the concrete surface are rotting wood. A waterproofing building material laid under the Mauerlat structure will help to avoid the destructive effects of moisture. For good waterproofing, two dense layers of material are used. You can use roofing felt or more expensive products.

In addition, it should be borne in mind that when using studs or anchors, holes must be made in advance in the surface of aerated concrete. But this task is more difficult than it might seem at first glance. The difficulty lies in the fact that using the building level it is impossible to install the fasteners exactly in a vertical position, especially in a liquid concrete mixture. Therefore, to begin with, it is worth determining where the bolts will be located, and how much they will deviate from the concrete. For this purpose, experts use a flat wooden board. It marks the exact location of the bolts. To do this, the board is applied to the extreme bolts and mark where the others should be. After that, the builders transfer the points directly to the bar, drill holes according to the marked points. Then you should place the holes on the fixed bolts and tighten the wooden block with nuts. With metal wire, work is much easier. To do this, 2 holes are drilled in the bar, the distance between which should be about thirty centimeters.

Workers thread a metal wire into the prepared holes, twisting the ends.

One of the most important nuances of the technology of building a house from aerated concrete is the fastening of the Mauerlat. The characteristics of the blocks do not allow to withstand high point loads; without taking structural measures, the walls will simply collapse. Properly executed fastening implies the laying of an armored belt, this stage is not recommended to be skipped. If it is impossible to organize it, the Mauerlat is in direct contact with the wall and fixed with wire, anchors, studs or dowels. The method is determined in advance; in the absence of experience, this type of construction work is best left to specialists.

Possible fastening methods

Depending on the type of strapping scheme, one of two options for attaching the Mauerlat to aerated concrete is selected: pouring a monolithic reinforced concrete belt around the entire perimeter of the building or placing fixing elements directly into the masonry or blocks. The first method, in addition to ensuring maximum reliability, contributes to the redistribution of loads, levels the walls and protects them from deformations, including shrinkage. The presence of an armored belt is mandatory when building in areas with seismic activity, building houses from aerated concrete over one floor, using heavy roofing materials, and complex roof shapes.

The standard instruction for its bookmark includes the following steps:

• Preparatory: calculation of fasteners and selection of the interval between them. The main guide is the layout of the rafters: with an equal number of attachment points to the Mauerlat should not coincide with the places where the studs are twisted.
• Laying U-shaped blocks on top of the last row around the entire perimeter of the aerated concrete wall. They act as formwork, the recommended width is from 25 cm.
• Assembly of a reinforcing frame from rods with a thickness of 10 mm. At this stage, it is planned to lay studs for fixing the Mauerlat with an interval of no more than 1 m, strictly vertically, with wire binding to the main rows. Particular attention is paid to the corners, in these areas the metal rods are bent to a length not less than the width of the belt. Similar actions are repeated along the entire perimeter of the bearing walls, including gables and partitions.
• Organization of an insulating layer of compacted polystyrene foam. It is placed closer to the outer edge of the aerated concrete wall.
• Filling the internal cavity with concrete with a strength grade of at least M200, compaction, removal of excess and careful leveling of the top layer. Cover with polyethylene and standard moisture care during the first days.

You can proceed to the next stage of tying the Mauerlat to the walls of aerated concrete in a week. All formwork structures are removed (they are used when pouring a monolithic reinforced concrete pad around the entire perimeter and width, this design is typical for brickwork, but is sometimes also used for gas silicate houses). Further, on top of the upper side in contact with the future Mauerlat, 2 layers of waterproofing are laid or coated, this step cannot be skipped. Attachment points are marked on a well-dried wooden beam treated with antiseptics and fire retardants. The easiest way to do this is by attaching it to the armored belt over the studs and hitting it with a sledgehammer, the holes are drilled according to the diameter of the rods (at least 14 mm). After that, it remains only to attach the Mauerlat to the aerated concrete wall and tighten it with nuts or washers.

The final stages of the work are difficult to perform on your own, you will need the strength of at least 2 people. In addition to the main walls, the armored belt is mounted on any areas on which the roof elements are supported (for example, ridge racks or beds). In the absence of experience, it is worth watching video instructions on the topic "how to properly fix the Mauerlat." If it is necessary to eliminate errors that have arisen during the masonry process, it is better to contact specialists, at least for advice. Installation of rafters is possible only after all work on fixing the Mauerlat and checking the quality of the connections is completed.

How is the Mauerlat attached to the wall in the absence of an armored belt?

Do-it-yourself laying of a monolithic tape is not always possible; in some cases, they resort to other methods of tying a beam. The easiest way is to lay 3-4 rows to the top of the steel wire between the blocks. Its length is selected taking into account the section of the Mauerlat: when folded in half, it should be enough for girth and twisting. The step depends on the distance between the truss structures. This option is often used when attaching a beam to the wall of a one-story house made of aerated concrete.

For light and small-sized buildings, a Mauerlat attachment for threaded studs made of galvanized or stainless steel is also suitable. They are mounted in masonry 1-2 rows before the upper edge, the minimum allowable penetration of such products into an aerated concrete wall is 2 times the height of the block. The standard length of the studs is within 1 m, the diameter is from 8 to 24 mm. If necessary, the protruding sections are then cut off.

Fastening the Mauerlat beam with wooden dowels is possible both when laying the armored belt and without it. They are long corks treated with antiseptics and well dried. They are mounted in an aerated concrete wall closer to the upper edge and connected to the Mauerlat by means of brackets. An alternative option is to lay them between the blocks, the number of pieces is not less than the number of rafters.

High reliability of fastening is provided with the help of anchors: mechanical or chemical. In the first case, the method consists in screwing expanding dowels with a cross section of 12-14 mm into aerated concrete. The second is in the use of chemical anchors (capsular or in the form of a tube with compounds based on polymer resins). The minimum depth of the hole to be laid is 2 rows of masonry.

The main advantage of anchoring is the ability to fix the mauerlat without complex organizational measures in the process of laying gas blocks, it is quite easy to carry it out on your own. However, the best results are observed with the most immobile hardware, that is, either laid simultaneously with the armo-belt, or fixed with the help of chemical compounds (in the latter case, welding is prohibited near the joints). The disadvantages of the method include high cost: of all technologies, fastening without an armored belt will cost the most, and the more reliable it is, the higher the final costs will be.

Violations of the Mauerlat fastening technology during do-it-yourself work include:

• The absence of a waterproofing layer between the timber and the upper part of the wall. Preference is given to modern bitumen-polymer mastics, roofing material is a budget option, polyethylene film is not suitable for these purposes due to its low strength. The minimum number of waterproofing layers is 2.
• Planting a mauerlat that has not been treated with antiseptics (the contacting side remains unprotected) or the use of wet wood.
• Installation of anchors or studs at an angle, the connection is unreliable.
• Incorrectly selected reinforcement for the frame, no overlaps (the recommended minimum if you need to continue the rods is 20 cm), close fitting of the metal to the walls of aerated concrete (plastic coasters are well suited to provide the required 5 cm).

When using raw wood, the Mauerlat is fixed with a nut, the reliability of the fasteners is periodically checked, and if necessary, they are tightened. This operation is carried out at least once a year for 4-5 years, until the end of shrinkage processes. A completely dried and well-established timber practically does not need to be tightened; it is examined for prevention purposes.

As a rule, a solid reinforced concrete belt is poured under such load-bearing structural elements. However, some amateur builders, apparently for reasons of saving time and materials, are trying to find ways to fix the Mauerlat on aerated concrete without an armored belt. Let's see how this is possible, and whether it is worth resorting to such a solution at all.

A few words about the importance of Mauerlat

What is a Mauerlat and why is it needed? To a person inexperienced in matters of construction, this tricky word often does not say anything at all. Meanwhile, we are talking about one of the most important load-bearing parts of the building structure.

What is the foundation - probably everyone knows. So, in terms of its functionality, the Mauerlat can be compared with a foundation tape. True, she is responsible for the loads transmitted from the entire building as a whole, and the Mauerlat is only for those that are formed during the operation of the entire roof structure - the truss system, roofing, insulation "pie", the inner lining of the slopes (if any) and etc.

And the loads here can be considerable, and what is most dangerous is to have a bursting direction perpendicular to the surfaces of the walls, that is, to work for their destruction. It's all about the angles of the roof slopes - this is what gives such a decomposition of the force application vectors, both from the severity of the roof structure itself, and under external loads - snow and wind.

Such bursting point loads transmitted from the rafter legs are especially dangerous for walls lined with piece material - brick or masonry blocks (which includes aerated concrete). This means that it is necessary to distribute the drop-down load as evenly as possible along the entire length of the wall. And, again, by analogy with the foundation tape, a powerful wooden beam can cope with this, which rests tightly throughout its entire length against the end of the wall.

The second remarkable quality of the Mauerlat is the significant simplification of installation work when installing the truss system. Agree that attaching each rafter leg to the main wall is much more difficult than, as they say, "tree to tree." With the presence of a Mauerlat, very wide possibilities for using various connection schemes come off, from “deaf” to movable, using a variety of fasteners.

As a Mauerlat, a wooden beam with a cross section of 100 × 100 mm and above is usually used (as a rule, depending on the massiveness of the roof structure, another 100 × 150, 150 × 150, 150 × 200 mm are chosen). Very often they rely on an unspoken, in principle, but effective rule - the thickness of the Mauerlat should be at least two thicknesses of the rafter legs.

Width - depending on the thickness of the wall on which it is installed. At the same time, they try to arrange the beam so that it does not fall flush with the surface of the wall either outside or inside. So it will be easier to protect the wood from the negative effects of the external environment, to insulate this rather difficult node in terms of ensuring normal thermal insulation. This rule is not mandatory, but if you read the advice of the masters, then all of them almost unanimously advise leaving at least 50 mm from the edge on each side.

It is possible to make a Mauerlat from a log, but such a solution does not seem to be optimal - the operations of attaching to the wall, and then inserting the rafter legs will become much more difficult and, accordingly, will require increased skills in carpentry.

It is clear that in view of the high responsibility of this element of the roof structure, for such purposes, they try to choose dried wood of the first grade, which does not have curvature, pronounced knotting, cracks, signs of biological decomposition, and other defects.

For Mauerlat, selected hardwood is generally recommended. But finding such material is not easy, therefore, high-quality pine is most often used, but only by exposing it to a very picky choice: saving on quality in this case is completely unacceptable.

By the way, the Mauerlat may not be wooden. For example, if it is planned to create a truss system from prefabricated or welded metal trusses, then a steel beam will also be used as a power plate - usually a channel or an I-beam. However, in the practice of private construction, such solutions are rarely resorted to - wood remains a "classic".

Mauerlat may not be used on walls made of timber or logs (its role will be played by the last row - the top trim), and on frame houses - for the same reason. Sometimes they refuse the Mauerlat when the walls are built from a material that is durable, resistant to point and bursting loads (for example, concrete), and at the same time the roof structure involves attaching the rafters to the outer extension of the floor beams. For walls made of piece materials, it will not be possible to do without a Mauerlat in any case.

It is clear that in order for the Mauerlat to fully perform its functions, the reliability of its fastening to the wall should not cause any concern. With concrete, stone, brick walls - it's easier, since there are many ways to securely fix the timber at the end of the wall. For example, when laying ceramic or silicate bricks, bookmarks are made from wooden blocks. This makes it possible then to use ordinary steel brackets for fastening the Mauerlat. But to complete such bookmarks with aerated concrete is an absolutely hopeless task, you don’t even have to try, since no reliability will be provided. We have to look for other ways, which will be discussed later in the article.

On aerated concrete walls, Mauerlat is recommended to be performed according to a “closed circuit”, that is, in the form of a frame that completely encircles the entire perimeter of the building - this is how the maximum reliability of the structure is achieved. However, this is not always possible - for example, in the case when gables are laid out from the same foam blocks. This means that the more reliable the fastening of the beam to the end of the wall should be.

How is a gable truss system calculated?

In the course of the presentation, we have already once referred the reader to the size of the rafter leg - the section of the Mauerlat depends on this to a certain extent. But, taking into account the angles of steepness and all the drop-out loads - read in a special publication of our portal.

How can I attach a mauerlat beam to a gas silicate wall without an armored belt?

First of all, a builder who faces such a problem must clearly answer the question for himself - “Is it really not possible for me to pour a reinforced concrete belt so as not to have problems in principle?” Why? - Yes, because any of the options proposed below is not without certain shortcomings. And besides - the very possibility of installing a Mauerlat without an armored belt is rather doubtful, and is accepted with many reservations.

No matter how much you look, it is unlikely that you will be able to find intelligible criteria when experts say unequivocally - yes, you can do without a concrete armored belt on this gas silicate wall. There are only many "ifs" in which, it seems, one can hope for the success of such a montage.

Aerated concrete prices

aerated concrete

• If the house or outbuilding is small (unfortunately, there are no evaluation criteria).
• If the roof has a not too complex and heavy structure (let's say that we are talking about simple ones from, for example, corrugated board or metal tiles - all other roofing materials, together with their crate, will be heavier).
• If the climatic conditions of the construction region do not imply a large snow load and wind pressure (and where is the guarantee that a weather anomaly will not happen?).
• If the design of the truss system will minimize bursting loads. This can be provided:

- The use of hanging stops, rigidly tied with horizontal puffs.

- The use of layered rafters, with obligatory support at the point of the ridge connection, if at the point of connection of the rafter legs to each other, a hinge connection is provided on the ridge, and the attachment point to the Mauerlat involves the use of movable, sliding joints.

In a word, the list of conditions in order to try to do without an armored belt (and even then without complete confidence in success) is quite large. And it is necessary, probably, to think ten times before choosing this particular path.

However, the Internet offers several ways to mount a Mauerlat beam directly on a gas silicate wall without pouring an armored belt. Let's try to understand them.

Mauerlat fastening with wire

One of the simplest methods, which is often used in the construction of brick walls. In this case, approximately 4–5 rows before the end of the masonry, bundles of steel wire with a diameter of approximately 3 mm (3–4 cores in a bundle) are laid between rows so that they look out from both the outer and inner sides of the wall. The length of the release of these "pigtails" is made such that it provides coverage for the Mauerlat beam mounted at the end of the masonry and allows for reliable twisting and tightening of the wire loop without any problems. The location step of such leash bookmarks is usually chosen equal to the installation step of the rafters, so that the attachment points of the Mauerlat fall between adjacent rafter pairs.

When the wall is ready, it is laid on its end. Then a bar is installed on top, leveled, and then a wire loop is created and tightened. Tightening is usually carried out with the help of a crowbar (mount), achieving the tightest pressing of the beam against the wall.

It would seem - here it is, the simplest solution. However, take a closer look: all the examples shown are only on a brick wall. They write that this method also works well with gas silicate blocks, only the laying of wire "pigtails" is carried out approximately two rows before the end of the masonry.

They write something, but it was not possible to find a single reliable evidence of the reliability of such a method with gas silicate walls on the Internet.

According to personal feelings - will the wire under heavy loads, and even more so - with possible vibration, for example, in strong wind, work like a “hacksaw blade”, gradually biting into the gas silicate block (which can be sawn with a hand saw)? After all, this is a violation of the integrity of the masonry, and a weakening of the fixation of the Mauerlat on the wall, with all the ensuing consequences.

In a word, not everything is so obvious...

Fastening the beam with anchors or dowels

It would seem - the simplest and most reliable way, proven by practice and time. Everything is so, but only if we are not talking about gas silicate. The increased fragility of this material may well give a surprise when a crack or even a chip forms when the anchor is tightened or the dowel is screwed in.

Of course, on sale in our time you can find a considerable range of fasteners designed specifically for aerated concrete walls. But, you see, it is one thing to fix furniture, interior items, or even a frame for wall insulation - and a completely different powerful one, which becomes the basis for the entire roof structure.

Considering that the holding properties of gas silicate are small, you will have to purchase anchors of maximum length - about 300 ÷ 500 mm, so that, taking into account the thickness of the Mauerlat beam, you can more or less reliably “hook” on the wall. But the cost of such long powerful anchors is considerable, so this must also be borne in mind.

The work on mounting the Mauerlat on the anchors is carried out approximately in the following sequence:

Illustration
	First of all, it is necessary to provide reliable waterproofing between the gas silicate and the stacked timber. Otherwise, at the place of contact of wood with other building material, a center of dampness will inevitably appear and, as a result, biological decomposition.
	For a waterproofing barrier, a strip of high-quality roofing material is quite suitable - it is laid so that it completely covers the entire end of the wall. If it enters a few on the sides, it’s not scary, since this one is easy to cut off later. The strip can be laid dry, that is, without the use of bituminous mastic.
	After that, a Mauerlat is laid on the end of the wall. In this example, a high-quality board 50 × 150 mm is used for it, which, by the way, looks a bit thin in terms of thickness. But the principle of fastening does not change from this.
	The beam is laid exactly in its place, as provided by the project, leveled.
	The necessary markup is carried out. In principle, in this case, it boils down to marking out the areas for installing the rafter legs - then the Mauerlat fastening anchors can be placed between them - and there will be no mutual interference.
	The place of attachment of the rafter leg is outlined. Anchors can be positioned arbitrarily, repeating the step of the rafters.
	Here it is, the anchor bolt. Let's make a reservation right away - in this example, an armored belt is still poured on top of the gas silicate wall, so the master uses relatively small anchors, 12 mm in diameter and 150 mm long. In mature concrete, such fastening will provide the required reliability. But if there is no armored belt, you will have to install the longest fasteners - up to half a meter.
	Further, a pen-shaped drill for wood (in this case, 12 mm in diameter) is installed in the drill, and through holes are drilled in the Mauerlat beam, up to the end of the wall. It is recommended to immediately sweep away the sawdust so that it does not fall back into the canal.
	After that, a puncher with a drill for 12 is used. Directly through a hole in the wood, a channel for the anchor is drilled into the wall material.
	After the hole is ready, an anchor is inserted into it. Further, the anchor must be hammered with a hammer for its entire length, until the washer stops under the nut into the wood.
	And the last step is to tighten all the anchors using the appropriate key, thereby firmly pressing the Mauerlat beam to the end of the wall.

Will such a connection be reliable? With concrete, yes. With gas silicate directly - the question is complex, even with a large anchor length. In any case, no studies or results of the study of experience on this issue on the Internet could be found - neither positive nor negative.

Let's focus on one more thing. Often, the length of the timber in order to lay out the Mauerlat along the wall in one piece is not enough, and you have to resort to splicing. Experienced carpenters can make very interesting and reliable interlocks, but for a non-professional, it will be enough to make a half-tree connecting knot. A prerequisite: at this place it will then be necessary to provide for fastening - an anchor or a hairpin in order to tighten the junction.

Prices for corrugated board

corrugated board

A similar approach is also used in the corners where the beams of adjacent walls are joined - a locking connection, followed by tightening with the selected fasteners.

In addition, in order to tie all sides of the Mauerlat into the most rigid frame, reinforcement of the connection with steel brackets is practiced at the corners. One of the diagrams above shows this well.

Another tip - if you have to join two sections of timber on the wall, then you should strive to ensure that they are approximately the same length. For example, on a wall with a length 8,5 meters it is better to use bars not 6 + 2,5 , and, for example, 4,2 + 4,3 m.

Technological innovations - chemical anchors

A dozen years ago, few people heard about these innovative methods of fastening parts in various materials. Today, chemical anchors are widely available for sale, however, it is not yet possible to call them publicly available at a price.

By the way, many of the home craftsmen carried out similar fastening technologies without special chemical anchors - we are talking about those cases when a mixture of epoxy and a hardener was poured into the hole made, and then the part was inserted - a reliable connection was obtained in a day.

The advertising that accompanies such chemical anchors ascribes to them the highest strength properties. True, one can already meet consumer complaints, although, perhaps, they are related to the fact that there are a lot of low-quality fakes of such chemistry on the market. And if we talk about reputable manufacturers of such materials, then we should focus on the brands Sormat, Hilti, Nobex, Fischer, Tox, Tecseal, Tecfix, Technox, KEW and some others.

By themselves, chemical anchors can differ in the principle of their application.

• So, one variety has a capsule (ampoule) layout.

An ampoule is inserted into the hole drilled under the anchor, which contains a one- or two-component composition, which begins to quickly harden after mixing and contact with air.

After laying the ampoule, the anchor (pin) itself is inserted into the hole, and hammered to the required depth. When clogging, the anchor destroys the ampoule, sucking fills the entire space of the channel. Including between the walls and threads of the stud. At normal air temperature, after 25 ÷ 45 minutes, the composition completely polymerizes, hardens, provides reliable retention and immobility of the anchor even under considerable load.

• Another type of chemical anchors involves the use of cartridges (tubes) with a polymer composition (usually two-component) and a special dispenser gun. The gun is similar in design to the one we usually use with silicone sealants or "liquid nails". And some types of chemical anchors are directly designed for such simple guns.

In addition, depending on the material of the wall, additional devices can also be used. For example, let's see how a chemical anchor is installed, which is designed specifically for porous concrete.

Illustration	Brief description of the operation to be performed
	The illustration shows the possible components of a set of chemical anchors "Fisher" - these are the cartridges themselves with compositions of different hardening speeds, dosing guns. The channel for any chemical anchor always needs to be thoroughly cleaned of dust - for this there is a special pump for purging and pumping out, brushes of different diameters. A drill with a special nozzle allows you to make conical holes (just what you need for porous concrete). And, finally, various adapters, guide adapters, mesh bushings for hollow walls, and stud anchors themselves of various lengths.
	In this case, we are interested in the topic of the article namely the gas silicate wall - porous concrete.
	The drilling of the channel under the anchor begins. For this, a special drill with a round stop-limiter and a spherical nozzle is used.
	First, a straight hole is drilled - all the way to the limiter.
	The stopper rested against the wall, and thanks to the spherical shape of the nozzle, the hole begins to be conical - as shown in the illustration.
	When the channel is ready, the drill is placed straight and carefully so as not to break the accidentally narrowed top of the cone, it is removed from the hole.
	After that, they take a hand pump - it is necessary to thoroughly clean the channel from dust. Purge begins with the pump probe fully immersed in the hole.
	Then the pump probe is gradually removed from the channel without stopping the purge. If necessary, use a round brush of the appropriate diameter. This purging operation should be repeated at least four times - the presence of dust drastically reduces the reliability of the chemical anchor. Ideally, it is necessary to strive for the channel to be completely clean.
	After cleaning, a plastic sleeve is inserted into the hole. It will “ennoble” the edge of the hole and, most importantly, ensure the position of the inserted anchor (stud) perpendicular to the wall surface.
	Chemistry is getting ready to work. A cartridge is inserted into the gun, a mixer nozzle is screwed on. A small release of the composition is made on any surface - you need to make sure that all components are completely mixed - this will show an even color of the outgoing mixture.
	After that, the spout is inserted into the sleeve that limits the hole, and the filling of the cavity with the composite composition begins.
	Typically, the cavity is filled to about ¾ of its volume.
	Next, an anchor-stud of the required length is taken and carefully screwed (in the literal sense of the word) into the plastic mass that fills the conical cavity - for this, at this stage, the effort of the fingers is sufficient. It is important to ensure that the stud takes a position perpendicular to the wall - the guide sleeve will help with this, but it still does not interfere with checking. The pin is screwed all the way into the wall.
	It remains to wait only 45 minutes - and at normal temperature (about +20 °C) the anchor will be ready for load testing.

What else is said about the advantages of chemical anchors:

• The fastening is considered high-strength, durable - the service life is estimated at 50 years.
• The used polymer composite is completely inert to atmospheric, biological, chemical influences.
• When installing such an anchor, there are no bursting loads inside porous concrete, that is, the risk of a crack or chip is practically eliminated.
• At the same time, the penetration of the composite into the pores of aerated concrete adjacent to the drilled channel ensures the maximum degree of adhesion of the chemical dowel to the wall material.

Well, now - about the shortcomings. There are not many of them, but judge for yourself:

• The cost of chemical dowels is high, and mounting the Mauerlat will cost a very impressive amount. Moreover, our task requires very deep channels with their complete filling with composite - so a fair amount of cartridges will be required.
• Chemical anchors are not resistant to high temperatures. It is clear that on the Mauerlat, temperatures above 100 degrees, in principle, have nowhere to come from, but nevertheless ...
• No reliable data on the timing and results of the operation of chemical anchors for attaching the Mauerlat to aerated concrete without an armored belt have been identified. That is, there are suggestions that it should seem to work out well - but there are no results of the tests carried out yet. Maybe you want to be the first?

Video: Hilti Chemical Anchor Demonstration

Mauerlat fastening on embedded studs

If, even before attaching the Mauerlat, studs stick out from the end of the wall at the right distance from each other, the installation process is simplified to the limit.

• Marks for the location of the studs are transferred to the beam - for this it is enough to lay the Mauerlat on top and tap a little - the studs will leave marks that will become the centers of drilling holes.
• Further, a waterproofing strip is “pricked” on these studs.
• Then a beam with drilled holes is strung.
• Wide washers are put on the studs, nuts are baited - and a completely understandable procedure for pressing the Mauerlat to the end part of the wall takes place.

Everything is very simple, but except for one thing - how to fix studs into an aerated concrete wall. This is where the difficulties begin.

There are such tips - a deep, about 500 mm, hole is drilled in aerated concrete masonry, a hole with a diameter of about 3-4 mm larger than the diameter of the stud. The channel is then filled with masonry adhesive or cement laitance. After that, a hairpin is inserted into it until it stops - and in this form it is left until the solution has completely set.

It would seem easy, but some craftsmen who have tried this method are clearly not enthusiastic about it - solutions can shrink, it is difficult to avoid void areas, and the quality of such a knot is still not the highest. Some fasteners can become loose due to dynamic load or vibration, and this is fraught with a general weakening of the structure, the appearance of cracks on gas silicate blocks - with all the ensuing sad consequences.

Another option for early installation of studs. In this case, they are welded perpendicular to the metal plates, which will be placed in the masonry joint before installing the last row of gas silicate blocks. The shape of the plates does not play a big role - for example, they can be as shown in the illustration.

The main thing is that the plates create a support for the stud and at the same time work against the pulling load. With this approach, holes are drilled in the blocks of the upper row in advance, before they are installed in the masonry, then studs are inserted there, if necessary, the edges of the block are “aligned” so that it does not skew due to the thickness of the plate. After that, masonry is carried out - and when the wall is ready, there is immediately a number of embedded studs for mounting the Mauerlat.

And yet, the most reliable installation of embedded studs is ensured only when pouring a reinforced belt.

Is it reasonable to refuse to fill the armored belt?

And now, on the contrary, a direct question to the reader - how serious are your reasons to refuse this simple, but very reliable, proven, guaranteeing the strength of the roof structure being created, the operation of pouring the armored belt? Let's take another look at how simple and clear it all is before making a final decision.

The process of pouring a reinforced belt is nothing complicated!

Illustration	Brief description of the operation to be performed
	If you look at all kinds of instructions and manuals on the construction of houses from aerated concrete blocks, the issue of attaching a Mauerlat beam to the end of the walls without a reinforced concrete belt is not even considered. And only somewhere in the text can there be a modest mention: as an exception, for example, on small outbuildings, with roofs of a small area, if the climatic conditions of the region do not imply a pronounced snow and wind load, etc. In a word, practically at your own peril and risk. Is it really so difficult to fill in the armored belt in order to get away from this dependence - “if” at once?
	By the way, there is nothing particularly difficult in this, that is, something that even a novice builder would not be able to do. Manufacturers of aerated concrete building materials have provided in their assortment a special type of blocks designed specifically for the last row of masonry. They have a characteristic shape, for which they received the name U-blocks (for their resemblance to this letter of the Latin alphabet). In fact, this is a non-removable formwork made of aerated concrete in the factory for pouring a reinforced belt.
	Look at the illustration - it shows various sizes of aerated concrete U-blocks. The smallest block (200 mm thick) has a symmetrical shape, all the others have one wall thicker than the other. This thickened wall should look towards the street - it is made wider for reasons of maximum preservation of thermal insulation qualities.
	The dimensions of the “channel” for the reinforced belt itself are not so large, that is, a lot of concrete is not required, and it will not be difficult to make it for a medium-sized country house on your own right at the place of work. Moreover, you still have to fill it manually, since the concrete pump in this case will not be an assistant - the “tape” is too narrow and small. The amount of concrete for this operation will be discussed below. It would seem, why even think about ways to do without an armored belt - isn't it better to start pouring it right away? However, many are stopped by the fact that U-blocks, which require less material during production, are also significantly more expensive, since they are usually sold by the piece. But it turns out that such blocks can be made independently, using standard wall blocks, or you can do without them altogether by applying other technical solutions.
	So, U-blocks can be cut from standard wall blocks.
	To begin with, of course, markup is carried out - the width of the cut fragment ...
	... and its depth.
	Lines are drawn along which cuts will be made. In this case, the master decided to cut a “channel” 120 mm wide and 160 mm deep. This will be enough for a reinforced belt.
	If walls were built from gas silicate blocks, then the master must have a tool for cutting them. Usually this is a powerful hand saw with a large tooth. They begin to make cuts along the marked lines - to the depth of the “channel” being created.
	To achieve evenness of the cut in depth, the block is sawn in turn, achieving the desired immersion of the saw, first with one ...
	... and then on the other side. By the way, we don’t have a picture, but judging by the assurances of the masters, such even and identical cuts in depth can also be made with a circular saw. True, the release of the saw may be insufficient (well, you need at least 100 mm of cutting depth) - finally, you can work with a hand saw. Why not an option?
	A block with slots made is placed "on the butt".
	Next up is the perforator. A drill is inserted into its cartridge - the diameter is not so important (usually 8 ÷ 12 mm is enough), but it is better to take a longer length, about 400 mm, so that the drilled hole reaches approximately the middle of the block. A series of holes are drilled along the line defining the bottom of the “channel” being created, with a distance between their centers of the order of 15 mm.
	Then the block is turned over, and a similar operation is carried out on the opposite side.
	After that, a light blow with a hammer is usually enough - and the fragment cut from three sides falls out of the block. By the way, these fragments, if they have not split, should not be thrown away - they can still come in handy during construction.
	And to fill the reinforced belt, there remains such a home-made U-block.
	If necessary, the remaining irregularities can be trimmed with a chisel ...
	... sweep away crumbs and dust ...
	...and send the finished block to the place of their storage before laying.
	After a sufficient number of homemade U-blocks have been prepared, they move on to laying the last row of the wall. Work usually starts from the corner.
	Glue for aerated concrete is prepared from a dry mixture. Blocks are laid out sequentially. Everything is as in ordinary masonry - first, glue is applied with a layer of the desired thickness ...
	…this layer is then leveled and spread with a notched trowel…
	... and then another gas silicate U-block is installed. Work continues in a similar way until the entire row is laid out - until a “channel” is formed for pouring the armored belt.
	Particular attention is paid to the corners and at the junction of the walls - here you will have to think about how to join the U-blocks so that the "channel" for the armored belt is not interrupted. One of the options is shown in the illustration, but other solutions are quite acceptable.
	To some, this approach may seem overly time-consuming, and, moreover, accompanied by a large amount of waste. Well, this is true to a certain extent, and it is quite possible to apply other methods of creating formwork for the armored belt. Here is one of them. To create the walls of this kind of fixed formwork, in this case, gas silicate blocks of smaller thickness are used - they are often called additional ones. For example, you can use blocks with a thickness of 100 mm - to create an external wall.
	A number of these blocks are laid on the adhesive along the outer contour of the wall (the illustration shows only an installation example).
	Any armored belt, due to the specific thermal properties of concrete, always turns into a powerful "cold bridge". To reduce this disadvantage, it is advisable to immediately provide for a layer of insulation - lay along the outer wall of the fixed formwork (if the width of the wall block allows) extruded polystyrene foam with a thickness of about 50 mm.
	On the opposite side, the wall of our "formwork" is formed by a thin block, 50 or 75 mm thick. This row is also installed on gas silicate adhesive.
	The result is something like this picture - a channel for further pouring of the reinforced belt (shown in the illustration with the reinforcing cage already laid). By the way, you can slightly reduce the depth of the “channel” if it turns out to be too large. At the bottom, also on glue, you can lay fragments cut out from additional blocks, so that the depth is in the region of 150 ÷ ​​180 mm - this is quite enough.
	There are more options. For example, on the one hand - the same gas silicate block 100 mm and a layer of insulation, and on the other - just a wooden (or OSB) formwork, pressed to the surface or set exactly along the end of the wall.
	But the option and generally without the use of gas silicate blocks. Wooden formwork is installed on both sides. But from the outside, along the formwork boards, a strip of expanded polystyrene 100 mm thick and a width corresponding to the height of the “channel” created for the armored belt is laid.
	Here is this option, so to speak, live - with the insulation laid along the outer perimeter of the formwork. Although the insulation is not mandatory in this case, it should not be neglected - this has already been mentioned above. But on the inner walls it is not needed - if it is also planned to pour a reinforced belt there, then only wooden formwork on both sides will be enough.
	After the formwork (in any of its versions) is exposed, they proceed to knitting the reinforcing frame. As a rule, for the armo-belt under the Mauerlat, too much reinforcement is not required - four rods of a periodic profile (class A-III) with a diameter of 10 mm are enough.
	The spatial position of the reinforcement bars can be provided in various ways. The "classics", of course, are clamps made of smooth or corrugated reinforcement, with a section of 6 or 8 mm. - about the same as on a strip foundation.
	But often this scheme is also simplified - it still looks “too heavy” for an armored belt along the top of the wall. If you look at the examples presented, then many masters use very non-standard solutions. This one, for example, cut squares from a ready-made welded reinforcing mesh for a screed - and uses them as a kind of clamp templates.
	Binding is done in the usual way - with the help of steel binding wire.
	And such a picture is obtained after linking - a neat spatial structure of four rods of longitudinal reinforcement.
	And here is another original solution. Apparently, the owner has the opportunity to inexpensively (or even for nothing) get waste from the production of metal products. One can only envy such creativity!
	Be that as it may, no one cancels the rules for knitting reinforcement, especially in areas of reinforcement (longitudinal connection of rods, turns, junction areas). Therefore, appropriate bends, overlaps, clamps, etc. are made. - all according to the rules of the strip foundation. By the way, pay attention to an extremely important nuance. The presence of a reinforced belt leaves practically no difficulties for the subsequent fastening of the Mauerlat - matured concrete will perfectly hold even conventional expansion anchors. And yet, before pouring concrete, one more operation can be done - install the studs in advance, linking them to the reinforcement cage. After the belt hardens, the master will immediately have ready-made reliable fasteners for the beam.
	There are also several options for installing studs. So, for example, a guide hole is drilled under them in the bottom of the channel, and the stud itself is linked to the lintel of the frame reinforcing structure (as shown in the figure).
	The hairpin can also be located with an offset from the center line of the armored belt - it all depends on its width and the planned place for laying the Mauerlat. The figure shows how the embedded stud is tied to the longitudinal reinforcement rods.
	Here it is shown how, for the sake of economy, threaded stud lengths are simply welded to transverse reinforcement stirrups. True, for this it is already necessary to have a very good command of the skills of electric welding.
	If you screw a nut at the bottom of the stud and put on a wide washer, the reliability of the resulting fastening will increase significantly. After the full maturation of the poured concrete belt, it will be almost impossible to pull out such a hairpin.
	The step of installing the studs is usually taken the same as the step of the future installation of the rafter legs. At the same time, it is desirable that these Mauerlat attachment points fall between the rafters - so that they do not interfere with further installation operations.
	After installing and linking the studs, it is recommended to close the upper threaded part, together with the baited nut, with a stretch film - so that the thread does not clog when pouring concrete.
	It is necessary to ensure that the reinforcement rods are located at a certain distance from the walls of the improvised "formwork" - so that a protective layer of concrete is created. For these purposes, you can use special liners - they will provide the necessary clearances from both the bottom and the sides.
	Concrete is being prepared. As a rule, for such an armo-belt, the M200 concrete grade is sufficient (but not lower). In a medium-sized house, a large amount of concrete is not required for these purposes - it is quite possible to do it yourself in a concrete mixer.
	Then the finished solution is fed up (by buckets), and gradually the “channel” of the armored belt is filled with it.
	It is very important to ensure that when pouring there are no unfilled voids. To do this, the poured concrete is carefully “bayoneted”, that is, it is pierced along the entire length of the filled section with a piece of reinforcement or a pointed wooden lath - this will allow air bubbles to escape.
	After “bayoneting”, the solution is compacted as much as possible with a trowel or spatula, while leveling the surface of the created belt.
	So they sequentially move on, along the entire length of the created belt.
	The belt is filled and aligned. This illustration shows a variant without studs - the owner assumes the use of conventional expansion anchors for mounting the Mauerlat.
	But the option - with linked mortgage studs. After pouring the belt and its final maturation, for the masters who will deal with the truss system, there are ready-made fasteners. In any case, the armo-belt must be given time for high-quality maturation - it is advisable to start further robots no earlier than a month after pouring.

As promised above - a few auxiliary materials:

Reinforcement of the strip foundation - how to do it right?

It has already been mentioned in the table that the principles of spatial reinforcement of the autumn belt are similar to the foundation tape - especially in matters of reinforcement at intersections, junctions and at corners. Details are given in a special publication of our portal. And in another article are given. Plus, in both articles there are convenient calculators for calculating materials.

And, finally, a calculator that will help you quickly and accurately determine the required amount of M200 concrete for pouring the armored belt, and the number of components for its manufacture.