How to choose fasteners for aerated concrete, types of fasteners

Attaching the Mauerlat to the walls is considered a purely technical issue, uninteresting and boring for most private developers. Not many of them know the purpose of the Mauerlat and the requirements for its design. Therefore, the owners of the future home rely entirely on the opinion of hired builders. And the majority of “experienced builders,” even if they just arrived from their villages and villages yesterday, insist on erecting an armored belt in order to attach the Mauerlat to it.

To understand the goal of the builders, as well as find out how fastening the Mauerlat affects the quality of the house and the developer’s wallet, you should start with a description of the basic concepts: Mauerlat, reinforced belt, characteristics of gas blocks and other porous wall block materials, calculation of loads on block walls.

Fastening building structures to aerated concrete

On such fragile walls it is necessary to fix not only wires and pipes, but also heavy structures: floors, roofing elements, etc.
In such cases, fixing self-tapping screws into aerated concrete is not a solution; a serious decision is needed. As a rule, it is carried out during the process of laying walls, when a monolithic reinforced concrete armored belt is made at the installation level of such structures. During pouring, studs and other embedded parts are installed into it, onto which the fastening is subsequently carried out.

If for some reason you did not make an armored belt, or did not provide mortgages in it, fastening is carried out only with chemical anchors.

Design features of the armored belt

Mounting the Mauerlat on studs without an armored belt

Armopoyas is a kind of reinforced concrete foundation for the roofing system. This structure is heavy and experiences strong wind, snow and tensile loads. Based on this, the roof needs a strong, powerful and stable support that can withstand the influence of external factors for decades.

The armored belt has the following device:

• Formwork. It can be made removable or non-removable. The first option involves arranging a cold attic, while the second option uses insulation (foam plastic, basalt wool) as formwork.
• Steel frame. Provides contour integrity and flexibility. Consists of fittings, square frames and corner parts. The parts are fastened using binding wire.
• Concrete. Gives the structure strength and shape constancy. It is made from crushed stone, sand and cement in a ratio of 3:3:1.
• Embedded parts. Serve for fastening the Mauerlat. Pins or studs are used.

The width of the armored belt corresponds to the parameters of the wall or is taken 5 cm narrower. The minimum height is 15 cm.

When choosing fastenings for aerated concrete walls, take into account such features

When choosing hardware, take into account the strength of the working surface, the dimensions of the parts and their resistance to corrosion.

The higher the density of the material, the stronger the aerated concrete. This indicator sets the load limits on the fastener. Technical characteristics in digital terms are indicated on the packaging of building blocks after the letter D.

The strength of the connection is affected by the size of the dowels. Thus, when fixing massive structures, products of large diameters and lengths are used.

The resistance of fasteners to corrosion ensures the possibility of their use when installing external structures and arranging unheated premises.

Scope of application

Chemical anchors in aerated concrete are used less frequently. It is used in cases where it is necessary to provide reliable fastening for massive objects. Mechanical anchors are not capable of supporting, for example, the weight of massive equipment.

Epoxy compounds are used mainly on solid bases. They are used for fastening:

• wall structures;
• beams;
• fences along roads;
• creating noise-insulating screens;
• when installing reinforcement outlets;
• when installing attachments.

This composition can be used:

• in a humid environment;
• under the water;
• both outside the building and for interior work.

Its composition:

• does not create stress in the structure of the porous wall;
• does not contain styrene;
• creates fastenings with smooth reinforcement.

The hardening of the mass depends on the air temperature. The time can last from 7-180 minutes. or 7-48 hours.

Polyester anchors are used to create:

• enclosing structures;
• when installing façade elements;
• for installation of translucent elements;
• during installation of utilities.

Typically, threaded rods are installed along with polyester compounds. The polyester anchor does not contain styrene. Therefore, it can be used on interior and exterior fasteners. The polyester anchor takes from 2 to 30 minutes to set and hardens from 25 to 180 minutes.

The anchor bolt for aerated concrete can be smooth or threaded if a vinylester anchor is used. It is used to create fasteners in wet substrates. It does not create unnecessary stress in the structure of aerated concrete. This adhesive solution is safe because it does not contain harmful substances. It is used for making internal and external fasteners. Does not create stress after installing fasteners in the structure of the aerated concrete block. Hardening is observed after 15 minutes or a day.

Epoxy acrylate anchor composition has become more widely used due to its properties. The period of setting and hardening of the composition is 2-24 and 15-180 minutes, respectively. Epoxy acrylate retains its properties when the temperature drops to -5°C, and also resists fire in case of fire for up to 2 hours. Epoxy acrylate anchor composition is suitable for anchoring floor slabs in aerated concrete houses.

Types of wall blocks

Aerated concrete material is divided into wall blocks - thick, massive structures for the construction of external walls (from 25 to 50 cm) and aerated blocks - structures up to 15 cm thick for the construction of partitions. The shape of aerated concrete wall blocks is of the following types:

• groove-ridge - characterized by the presence of several ridges on one side of the block and grooves on the other side, such a system improves the installation of blocks and the reliability of laying the material; when laying such a structure, no glue is needed, which eliminates the formation of cold;
• straight - traditional blocks, used for the construction of external and internal walls, may have handles for gripping;
• arc-shaped - used in the construction of round structures;
• U-shaped - used primarily for the construction of arches, doorways, lintels, columns and other decorative structures.

Why you shouldn’t attach excessively heavy structures to gas block and foam block

About the gas block

Autoclaved aerated concrete has thermal conductivity characteristics close to foam plastic because, like insulation, it contains air bubbles in its structure. At the same time, foam plastic has almost zero load-bearing capacity.

Why should a gas block be so much more durable? It should be noted that it copes well with a load evenly distributed over an area, for example, in wall masonry. But it does not tolerate local loads from ordinary dowels and anchors, that is, it simply does not hold

And no matter what the manufacturers of such blocks say, you need to load the material locally with great care - use special fasteners, spread them over a large area, do not hang very heavy structures without a metal frame

Excessive load on aerated concrete can lead to similar consequences

The weakest point of an aerated block in terms of load-bearing capacity is variable pressure. Periodically attaching and removing any heavy structure from an anchor will contribute to the crumbling of the material around the fastener and failure of the attachment point.

About the foam block

Foam concrete is used less frequently in modern construction, and on average it is heavier and stronger than aerated concrete. Of course, strength depends on the class of the material - the higher the class, the more durable it is, but at the same time it loses somewhat in its heat-insulating properties.

Perhaps we can say that the foam block is somewhere between concrete and aerated concrete in terms of strength. However, when choosing an anchor for foam concrete, it is better to be guided by the same principles that apply when using aerated concrete.

Strong arguments against the armored belt

Most craftsmen involved in the construction of buildings made of aerated concrete are confident that installing an armored belt can solve all problems with installing the mauerlat and roof. In fact, this is not entirely true, for one simple reason - the future house is being built from extremely weak aerated concrete. Therefore, it is impossible to transfer the techniques and technologies of the armored belt, which successfully work on brick, block and concrete buildings, to aerated concrete walls.

There are only two fundamental objections to the armored belt:

• First of all, with any manufacturing scheme, the reinforced belt can be secured only to the top row of aerated concrete, so the roof has to be made with the same restrictions, as in the case when this belt is not present. The concrete frame redistributes the thrust load well, but all the forces from the reinforced belt fall only on the top row of aerated concrete, hence the appearance of cracks along the upper edge of the walls;
• Attaching the Mauerlat to an armored belt means creating huge problems with a cold bridge in that part of the roof where aerated concrete is least ventilated. Even laying a layer of EPS insulation helps little; you have to look for ways to install vents to remove condensation from the reinforced belt.

The third argument against concreting is related to costs. The installation of reinforcing tape will cost an amount approximately equal to a third of the estimate for the construction of the foundation. For a house 4x8 m this is approximately 60-100 thousand rubles. It is clear that it is much easier to fasten the Mauerlat and roof frame to a Mauerlat rigidly connected to a concrete reinforced belt. Sometimes master roofers even refuse to install a roof on aerated concrete without an armored belt, but technologically this is quite possible.

Characteristic

Aerated concrete is rightfully recognized as one of the most practical and affordable materials. It makes durable and strong houses, as well as reliable outbuildings. However, you need to take into account that this material has a cellular structure, when faced with which you need to take into account many nuances. The main characteristic feature of this material is its fragility and pliability. Porous blocks can be trimmed or cut off the excess part without any extra effort. And we must also not forget that special fasteners are used for such a structure. Traditional fasteners, as a rule, do not adhere well to such foundations, which is why the whole point of their use is lost.

For aerated concrete, special dowels should be used. The design of such parts is a sleeve in the form of a spiral, on the surface of which there are ribs. When screwing in a self-tapping screw, the last elements become wider, so they fit firmly into the loose aerated concrete surface. This simple but effective device can easily withstand impressive loads. With the use of special dowels, home owners have the opportunity to hang heavy decorative objects of any size on the walls.

Modern manufacturers produce these types of dowels in two variations. They differ in design features.

• According to the shape of the fixation ribs. Such fasteners can be equipped with a classic helical spiral or have cone-shaped ribs. The edges of the latter may resemble spiral-like blades.
• By installation method. The dowels are either screwed into the base or driven into it. Screw-in types are considered to be the most reliable. It is recommended to use driven-in fasteners if the aerated concrete floor is planned to be equipped with a collet.

How to lay a gas block: a step-by-step guide

The first row of blocks requires increased laying accuracy, since the accuracy and ease of laying subsequent rows and the wall as a whole depends on it.

The installation of waterproofing units between the foundation (basement, plinth) and aerated concrete masonry must be carried out in accordance with the decisions made in the project or in accordance with the album of technical solutions.

A mooring cord is stretched between the lighthouse (outer) blocks.

The blocks are laid on opposite sides of the wall, further laying is carried out from the outer blocks to the center using a cord.

The height of the beacon blocks is selected based on the block located at the highest point.

If it is necessary to obtain a cut block, the cut is made with a hacksaw for aerated concrete using a square. In multi-story construction, the use of a band saw is recommended. After cutting, be sure to clean the surface with a sanding board.

The first row of blocks is laid on a leveling layer of cement-sand mortar.

The height of the first row of blocks is adjusted using a mooring cord stretched between the outer blocks of the wall. The position of the blocks is controlled by a level and adjusted using a rubber mallet.

Existing unevenness in the masonry is eliminated using a sanding board or plane. Small dirt and dust are removed with a brush.

Subsequent rows are laid on a special adhesive solution.

Fastening building structures to aerated concrete

In general, the process of installing fasteners is similar for all options. First of all, a hole is made, and then the cartridge is inserted. The only difference can be with a chemical anchor, since it uses glue.

Chemical anchors are secured as follows:

1. Preparatory work. You need to drill a hole using a drill.
2. Next, the hole needs to be cleaned of dust. To do this, use a brush or a medical bulb.
3. A cartridge with a chemical composition is installed. To do this, you need to insert a capsule with glue into the recess. The last one is squeezed out.
4. An anchor is screwed into the hole.
5. You need to wait until the glue dries. There are times when you need to wait 2 days for complete drying. It all depends on the composition, but temperature, humidity and other environmental features are also considered important factors.
6. Once the compound has hardened, you can install the washer and nut.

The installation process using a mechanical anchor, dowel nail or self-tapping screw is the same, but without the use of glue.

This is what the fastening looks like inside aerated concrete.

Video on the topic:

Each fastening method has its own advantages and disadvantages. When choosing, you should take into account the material, density, and characteristics of the room.

Previous entry How to attach a window sill to a plastic window Next entry Features of attaching gates to brick pillars

Fastening with metal studs

A metal stud is a steel rod with a metric thread, having a diameter of 10-16 mm.

Installation of embedded parts can be carried out in two ways:

• in the process of assembling the frame by welding;
• connection to reinforcing bars using tie wire.

Fastening with metal pins.

If you plan to lay the Mauerlat without a monolithic belt, then a metal plate with a thickness of 1.8-3.0 mm and a size of 100 x 100 mm is welded to the bottom of the part. The devices are embedded into the masonry to a depth of 40-60 mm. Upon completion of installation, the upper part of the rod should rise 3-5 cm above the surface of the beam.

Installation of studs into a finished monolithic base or solid masonry of solid gas blocks occurs as follows: every 1.2-1.5 m, holes are drilled with a depth of at least 20-30 cm and fastening parts are installed.

The Mauerlat is lowered onto the prepared structure and pressed in order to make marks for the holes with pins. They drill the beam, and when all the samples are ready, they string the profile onto the rods, throw on washers and nuts. Check the level of the bearing and tighten the connections.

The number of studs under the Mauerlat must correspond to the number of rafter legs in the roof structure.

Dowel

The part is a spiral-shaped bushing with ribs on the surface. At the moment the screw is screwed in, they expand, due to which they firmly fit into the soft surface of the base. Such fasteners can be made of galvanized steel or plastic.

The first option is the most common and is considered the most expensive. It is used when installing profiles, installing attachments and furniture, and fixing various pipelines. Such fasteners have become widespread in fire-hazardous spaces.

Metal dowels for aerated concrete are produced in 2 modifications, which differ in design features and installation methods. The parts can either be screwed into the base or driven into it. The latter option is used if the aerated concrete floor is planned to be equipped with a collet.

Based on the shape of the fixation ribs, fasteners with a classic helical spiral and dowels in the form of a cone, equipped with spiral blades, are distinguished. The design of metal elements also provides for the presence of a locking flange or cuff, thanks to which the part will not rotate.

Corrosion resistance is the main advantage of plastic products. The materials used for them are polypropylene and polyethylene. The positive characteristics of the parts include their efficiency, environmental friendliness, and immunity to aggressive environments. Such dowels are not intended for outdoor work, since with the onset of cold weather the plastic may burst.

A separate group consists of fasteners for aerated concrete made of nylon. They are more wear-resistant, so they can be used for cladding facades. Together with them, galvanized screw elements with 2 types of heads are used - countersunk or hexagonal. The disadvantage of this type of fastening is the high price.

Depending on the scope of application, there are several types of dowels:

1. Universal. It can be mounted in any concrete surface. In a solid base, fixation occurs in a standard way. In a cellular coating, the product is rolled into a persistent knot. However, the load-bearing capacity of universal dowels is lower than that of spacer elements.
2. A dowel-nail that has a wide range of applications. At the moment of fixation, a nail is inserted into the fastener, rather than a screw being screwed in. In order to avoid turning the part, use a sleeve.
3. The “pancake-like” structure of the frame dowels allows you to reduce the load on the porous surface of the block.

Load-bearing wall masonry

The next row of walls is laid after the cement mortar of the first row has set. The laying of the second and subsequent rows is done with dressing in half a block. In some places, block overlap is allowed less than half a block, but not less than 10 cm.

The position of the blocks, as when laying the first row, is controlled by a stretched mooring cord and level.

The mortar is applied to the surface of the blocks using a trowel or carriage made to fit the width of the masonry or a trowel used in tiling work. The solution must be applied evenly over the surface of the masonry.

Using a trowel, the solution is also applied to the vertical surface of the blocks.

The project may indicate that the adhesive solution is not applied to the vertical surfaces of the blocks of the tongue-and-groove system; such a decision is justified if subsequent double-sided plastering of the walls is provided, and the load on the block is significantly lower than the load-bearing capacity.

The ends are cleaned using a sanding board or plane. The length of the outermost block must be at least 10cm.

The mortar protruding from the seams is removed using a trowel. Rubbing the solution is not allowed.

The alignment of the masonry is repeated after laying each row of blocks.

After laying each row, the deviation from the horizon will be checked using a level.

If it exceeds the established tolerance, the deviation is eliminated when laying subsequent rows. After 2-3 rows in height, the evenness of the masonry is checked with a level.

Tool and surface features

Installation tools:

• electric hand drill;
• drill bit with pobedite tip;
• hammer;
• a wrench or screwdriver for screwing in a screw;
• adhesive mixture for chemical anchor;
• special gun for glue mixture.

The main condition when installing objects and accessories is the correct choice of hardware.

Aerated concrete, having a porous structure, is a relatively fragile material, so the question arises - what kind of hardware is needed to ensure that the fastening is reliable and meets all the operating requirements of the structure.

There is a wide range of products that make it possible to fasten structures reliably and quickly.

From the video below you will learn about fasteners for aerated concrete.

Why does foam concrete need special fasteners?

Foam blocks are made from water, sand, cement and a special foaming agent. The blocks are cellular, the material is fragile enough for installation of various fasteners.

The main distinctive features of foam blocks: low weight, low density, high level of hygroscopicity, porous structure. For the most part, properties act as advantages during the construction and operation of buildings, but not at the moment of attaching some objects to the walls.

The structure of foam concrete is porous, the adhesion to materials is not very good, so the blocks cannot always cope with the loads, and therefore special dowels are provided for them.

Properly selected fasteners for foam blocks will not only secure equipment or furniture with high quality, but will also strengthen the working structure and significantly increase the percentage of permissible loads.

Fasteners for foam blocks require a certain design of fixing parts - they usually consist of the following elements: a screw, a ring, a half-ring, a side, an empty sleeve with a spacer. Many anchors are made with teeth, which become a reliable obstacle to the part turning.

There are also chemical anchors for foam blocks, which are created specifically for use and provide maximum quality of fastening. In this case, the main task of the dowel is to create internal support in the block during the expansion process inside the aerated concrete and preserve the fragile material from destruction.

Dowels can be of different diameters and lengths, made of metal or plastic, and are supplied in packs of 50-1000 pieces. According to the scope of application, they are intended for external/internal work, according to the installation method - driven, screwed and others (chemical anchors are distinguished separately).

Alternative ways to install kitchen furniture and equipment

There are other ways to hang kitchen cabinets or appliances. Most often, structures similar to plumbing frames for installations are used. These are support systems that represent a supporting frame with an emphasis on the floor and technological holes for installing fasteners. These frames do not have to be attached to the walls, but it is difficult (if not impossible) to ensure their stability using other methods. The advantage of this type of hinge is reliability, the ability to adjust the height of the frame to a given height, and high load-bearing capacity. In addition, you can use frames (or supporting slats) of different sizes to suit the existing set. The frame can be attached to the walls at randomly selected points where it is more convenient to install anchors. In a similar way, you can hang not only kitchen cabinets on aerated concrete, but also equipment or heating devices.

Chemical anchor

This type of fastening, such as a chemical anchor, is a fairly new and already in demand method. The builders appreciated it. Chemical anchoring has its advantages and disadvantages. The advantages of a chemical anchor include:

• high load capacity factor on fasteners;
• compliance with GOST, the chemical composition is safe and environmentally friendly;
• versatility, it is used for any building material;
• high resistance to weather fluctuations and low temperatures;
• low price when compared with steel anchors.

The disadvantages include:

• strict adherence to technology;
• purchase of special equipment, namely brushes, pumps, guns and drills;
• additional time for the chemical solution to harden.

Chemical fasteners for foam concrete include a threaded steel pin, maybe a special rod, a chemical mixture, and additional bushings.

Chemical anchor fastening sequence

1. Use a drill to make a cylindrical hole. Then it needs to be shaped into a cone with an expansion in depth.
2. The finished hole is thoroughly cleaned. You can use a pump for this.
3. A centering sleeve is inserted into the base.
4. A chemical solution is poured into the hole through the sleeve; a construction gun is used for this.
5. The threaded rod (stud) is screwed in.
6. Leave time until the chemical solution hardens completely.

The chemical anchor kit includes an easy-to-use package with a dispenser. Installation is easy, while achieving high structural strength.

Fastening chemical anchors

And so, for fastening light structures and decorative elements, ordinary self-tapping screws are quite suitable. They can be designed for working on wood or on cellular concrete. Nails for aerated concrete should have a wedge shape or a curved tip inside the concrete cavity.

For heavy structures, such as plumbing fixtures, kitchen cabinets, boilers, it is worth using foam concrete fasteners with wedging dowels. Reliable fixation is achieved precisely thanks to the internal stop. All hardware must be resistant to corrosion. This especially applies to mountings on an external wall.

Selection of material and calculation of parameters

When choosing a material, you need to pay attention to the structure of the wood, the absence of curvature and the integrity of the surface. Products must be free from knots, cracks and traces of biological influence. The moisture content of purchased wood should not exceed 8%.

The Mauerlat is made from a wooden rectangular profile with dimensions:

• 80 x 180 mm;
• 100 x 150 mm;
• 100 x 100 mm;
• 150 x 150 mm;
• 200 x 200 mm.

The choice of beam section is influenced by the following factors:

• number of floors and external dimensions of the building;
• design features (number of slopes, presence of an attic, etc.);
• roofing material;
• climatic conditions of the region.

Dimensions of wooden beams.

The weight of the timber used is calculated as follows:

• Determine the cross-sectional area - multiply the width by the height.
• We multiply the resulting value by the perimeter to obtain the volume of the material.
• We multiply the result by the specific density of wood - in this way we calculate the weight, or the amount of load that the Mauerlat will exert on the external walls.

The length of the profile should be such that the number of connections on one side of the building is minimal. The standard size of the produced material is 3-6 m, so for a distance of 8 m you need to purchase 2 segments of 6 m each.

When choosing the height of the profile, it is necessary to take into account that the connection of the rafters to the Mauerlat is made by cutting, and 50% of its actual size is used.

Tips and tricks

When installing dowels into a gas block, you cannot use a screwdriver, since this device runs on electricity, which makes it more difficult to control. Such a device can strip the thread by twisting the screw

When making a hole for dowels in a gas block, it is important to note that they should not be larger than their diameter. Otherwise, the fasteners simply will not hold securely in the base

The depth of the holes should be slightly greater than the length of the dowel. The tip of the screw must leave the dowel for the fastening to be as reliable as possible.

Many people, having become acquainted with dowels, begin to use them at any opportunity. However, experts do not advise using too powerful fastenings if you plan to hang hooks, pictures and other small items. For such purposes, simple plastic fasteners, the size of which is about 8 mm, are more suitable.

About fastening for aerated concrete - a nylon dowel and a metal dowel (crocodile), see the following video.

Types of fasteners and performance of work

The type of product is selected depending on the expected load:

• for fastening hanging mirrors or lamps, nylon dowels with a cross-section of up to 12 mm are suitable;
• when installing pipelines and bulky objects, choose metal parts;
• frame types of fastenings are used to fix window and door frames;
• universal facade dowels are used when installing external profiles for facing slabs;
• Only light objects are attached to wood screws - photo frames or decorative elements.

Installation is carried out in several stages.

In order for the products to fit tightly into the base, it is necessary to drill the holes correctly. To do this, it is best to use a hammerless drill or a hammer drill with the impact turned off. The drill should have a cross-section 1 mm smaller than the fastener itself. The only exception is steel hardware. For them, the hole will be reduced by 2 mm.

After cleaning the recess from concrete dust, install a dowel. The plastic fastener is screwed in using a screwdriver. Metal parts are driven into the mounting hole with a hammer. During the work, it is necessary to ensure that the product does not warp.

At the final stage, screw in a self-tapping screw or a standard mounting bolt. In this case, it is not advisable to use an electric tool, since when connecting to an aerated concrete block, the screw element may be damaged.

What is a Mauerlat and why is it needed?

Mauerlat is a supporting element of the rafter system that takes the load from the rafters and transmits it through the walls to the foundation. In wooden houses, it is called a mother log or timber, since the role of the supporting structure is often performed by the upper crown of the building. You can also sometimes hear from builders the distorted “murlat” - this is a slang name usually used by residents of the southern regions.

Installation of the rafter system begins with laying the Mauerlat - it serves as the basis for the rafters. Rigid fastening of the Mauerlat to the walls turns the point load from the rafter legs into a distributed one. As a result, the considerable weight of the roof presses not on individual sections, but on the entire upper surface of the wall. The photo below clearly shows the Mauerlat: what it is and how it works.

Why do you need a Mauerlat?

Having read the definition of what a Mauerlat is in roof construction, you can immediately name the main problem that this element of the rafter system solves. This is the collection of point loads from the rafter legs and its uniform distribution along the entire length of the walls of the house. But load distribution is not the only function of the Mauerlat.

So, the Mauerlat connects the rafters into one structure . This is especially important for a hanging rafter system where there is no ridge. Without a Mauerlat, the roof frame will simply fall apart into several triangles, which will work separately. With all the ensuing consequences in the form of low strength and stability of the structure.

The third function of the Mauerlat is to secure the roof of the house and withstand wind loads . Air currents that push against the wall of the house rise and create a force aimed at lifting or overturning the roof, depending on its shape and the angle of inclination of the slopes. Mauerlat prevents the roof from falling off by connecting it into a single system with the walls of the house.

In a layered rafter system, the Mauerlat is needed to compensate for the thrust load from the rafters . If in a hanging rafter system this function is performed by the tie and crossbar, then in a layered one only the Mauerlat prevents the rafters from folding under their own weight and the total mass of the roofing pie and snow load.

How does the load act on the rafters and mauerlat?

Another Mauerlat is an even support for rafters , which can be set strictly horizontally along its entire length, even if the upper surface of the wall is not level. Of course, it will still be necessary to correct very severe defects in the masonry, but a slight unevenness of the surface is acceptable.

If we simplify and try to reduce all the functions of the Mauerlat to one, then we can say that this is the foundation of the roof. Therefore, just as a house cannot be built without at least some kind of foundation, so at the base of any roof there must be a mauerlat.

What is the Mauerlat made of?

In most cases, the Mauerlat is made from solid pine timber or 2-3 boards nailed together. You can also use a rounded log, cut on one side so that it fits tightly to the surface of the wall.

If the house has a metal rafter system, then the mauerlat is made from an I-beam, channel or profile pipe. But in this case, it is necessary to calculate the loads from metal trusses in order to select the correct section.

Mauerlat length and cross-section

Mauerlat is laid along the entire length of the wall. For houses with hipped and hipped roofs, it is connected into a frame that encircles the entire building. The Mauerlat united into one contour is what makes such roofs strong and stable. For houses with gable and pitched roofs, two mauerlat beams are laid on opposite walls and, as a rule, are not connected. But flat roofs in regions with medium and high snow loads, as well as large-area roofs, can be reinforced with two additional beams on the gable walls to get the same frame.

What timber and boards are used to make the Mauerlat

The cross-section of the Mauerlat is calculated when designing the rafter system. When constructing private houses, it is most often made from 150×150 mm or 150×200 mm timber. Small roofs can be supported by 100x150 mm timber. The maximum cross-section of a wooden mauerlat for private houses is 200x200 mm. Such timber is used in the construction of roofs of spacious cottages, as well as for medium-sized roofs with gentle slopes. A beam of larger cross-section will itself place a heavy load on the walls of the building. In addition, there is a rule: the width of the larger side of the mauerlat beam should not be less than 1/3 and more than 2/3 of the wall thickness. Not to mention the fact that even a 200x200 mm beam is difficult to lift and lay on the wall, and lifting a mauerlat with a larger cross-section becomes a non-trivial task.

If the Mauerlat is prefabricated, then it is made from boards with a thickness of at least 50 mm. Usually these are 150x50 mm boards, since they make a square Mauerlat. The prefabricated mauerlat is fastened so that the boards lie on the wall in a stack, and do not stand on it with their ends.

Material requirements

The Mauerlat must withstand an impressive load, which for small houses reaches 4-7 tons, and for large cottages often exceeds 10 tons. Of course, such weight does not lie on the slopes all the time, but only in the snowy winter, but this does not make the task much easier. Considering the magnitude of the load, strict requirements are imposed on the materials for the Mauerlat:

1. Lumber must be thoroughly dried . According to GOST 20850-2014, wood moisture content should not exceed 12%. It's even better if the humidity is less than 8%. Under-dried timber can become deformed and crack under load. Helical warping is especially dangerous when the beam seems to twist around its axis. This jeopardizes the load-bearing capacity of the entire rafter system.
2. You can only use timber or boards without wood defects. Wane, cracks, knots, areas affected by rot, disease or fungal mycelium are unacceptable. The length of fused (healthy) knots should not exceed 2/3 of the section of the beam, otherwise at this point the Mauerlat will work less well in compression/tension, which can lead to the appearance of cracks.
3. The wood must be treated with an antiseptic and fire retardant. The optimal treatment is to immerse timber or boards in a bath of solution, since this way the impregnation will evenly penetrate deep into the structure of the wood along its entire length. If wood impregnated by submersion is not available, the Mauerlat beam is processed manually, applying an antiseptic and fire retardant with a roller or spraying the solution with a spray gun. It is important to ensure that the wood is completely covered with a protective composition, without any unpainted areas.
4. It is desirable that the Mauerlat be solid. If there is no timber of the required length, it can be spliced ​​under two conditions. Firstly, the joint should be approximately in the middle of the wall; you cannot splice the mauerlat near the corners of the house. Secondly, the parts of the mauerlat are connected only by cutting into half a tree; end-to-end installation is unacceptable.
5. When using rolled metal, it must be free of cavities, welding defects and rust . After installing the metal trusses, it is necessary to clean the welds and coat the metal with two layers of primer, and then paint.

When constructing temporary structures, the requirements for lumber are not so stringent. Let's assume wane and higher wood humidity; timber is usually not treated with antiseptics. But this is only if the structure is truly temporary - in 2-3 years, even with such a Mauerlat with the rafter system, nothing bad will happen.

Fasteners for cellular concrete

Using ordinary wood screws, only very light objects such as photo frames can be attached to aerated concrete. In all other cases, special fasteners will be required.

Fastening requirements

When choosing which fasteners to use for aerated concrete, you need to consider the following points:

The density of wall blocks, indicated in product labeling by numbers after the letter D. The higher it is, the fewer pores in the material, and the stronger it is. The load limit when pulling out fasteners depends on this indicator, and the manufacturer’s instructions on the packaging contain this information.

The numbers show how many kilograms are in a cubic meter of material

The fastener parameters are its length and diameter. The larger they are, the greater the load it can withstand. The load-bearing capacity must also be indicated on the packaging or certificate.

Chemical anchors have the highest load-bearing capacity

Corrosion resistance. This parameter is especially important when fastening into aerated concrete is carried out from external walls or in unheated rooms. Steel hardware must be coated with a protective layer.

Punch for aerated concrete

Mounting options

Let's take a closer look at which aerated concrete fasteners are used most often.

Let's start with the traditional types:

All these elements may have other varieties that differ from the images shown in the table. For example, turbo dowels with self-tapping threads are made from nylon.

Turbo dowel FTP K

And made of galvanized steel - four-leaf toothed expansion dowels. Their segments move apart when the screw is screwed in, reliably biting into cellular materials.

Steel expansion dowel

As already mentioned, one or another hardware and fastening method are chosen depending on the expected load.

If you need to fasten aerated concrete shelves, you need to carefully drill at a right angle, insert a dowel into the hole and screw a screw into it.

Shelves with covered mounting on aerated concrete wall

• And to hang a light picture or install an electrical switch, a simple self-tapping screw screwed at an angle of 45 degrees to the wall is enough.
• If you need to securely fasten heavy equipment or install a metal entrance door, it is best to use chemical anchors.

When installed, they are capsules made of synthetic resins and organic polymers that seal holes in a wall made of aerated concrete, firmly holding a metal rod or threaded rod in it.

The advantages of such fastening include exceptional reliability and durability, the adhesive base is not susceptible to thermal expansion and resistance to aggressive environments.

No special qualifications are required for fastening with chemical anchors; everything can be done with your own hands.

For this:

• A hole of the required depth is drilled in the wall, its bottom is slightly expanded by oscillating movements of the drill;
• Construction dust is blown out of the hole, and a sleeve is inserted into its neck;
• The cavity is filled with adhesive solution using a mounting gun;
• An anchor rod is immediately installed into it;
• After the solution has hardened, fastening can be done.

The price of such fasteners is higher than that of other types, but the reliability does not raise the slightest doubt.

How to hang a TV on a wall made of aerated concrete?

Mounting even a light TV on the wall must be reliable. The equipment is not cheap, so that if it falls, it can be immediately replaced. In addition, damage to the TV can cause a fire. Therefore, it is better not to take risks, but to secure such items correctly.

Mounting a TV on a wall made of aerated concrete

You need to proceed as follows:

1. Make a hole in the wall using a hammerless hand drill or a hammer.
2. Drive a wooden bushing with a diameter of 2–3 cm into it.
3. Install metal fasteners into it.

To increase adhesion, the dowel can be placed on a special glue or any sealant. The fastening will be reliable and durable. It can also be used when you need to hang a cabinet on a wall made of aerated concrete. The main thing is to choose fasteners that are proportional to the weight and dimensions of the furniture. And, of course, you should think twice before hanging something heavy not on a load-bearing wall, but on a partition made of aerated concrete.

Classification of self-tapping screws for aerated concrete and foam concrete blocks

Dowels for self-tapping screws

Without dowels, self-tapping screws for aerated concrete are not often used due to the porous structure of the blocks. They are used for fastening lightweight structures. Thus, they can easily secure a reinforced mesh to an aerated concrete surface before applying plaster. For such fastening, self-tapping screws with a wide pitch and a length of at least 10 cm are selected.

In this case, it will not be possible to use a hammer drill, since the aerated concrete will crumble greatly. A drill with a thin drill bit is used. There is a way to screw self-tapping screws into a porous surface using machine oil. A few drops of oil are added to the prepared hole, so the hardware can be easily screwed in. The hardware will fit tightly, and it will be difficult to unscrew it in the future.

Self-tapping screws with a herringbone profile can be hammered into foam concrete blocks. The consumables along with the dowels are driven in “forever”; it is almost impossible to dismantle them. The work must be done quickly so that the prepared hole does not begin to crumble.

How to use?

The principle of installation of dowels is the same as for other types of fasteners. You need to act in the following order:

• first you need to prepare holes for the dowel, which should be smaller than the diameter of the fastening; for example, for 8 mm fasteners you will need to use a 7 mm drill;
• if you take a tool such as a hammer drill, then you need to turn off the impact mode; of course, it is advisable to use a drill, since it is more effective;
• the plastic fastener must be carefully screwed in using a screwdriver; if metal parts are used, then they should be driven into the mounting hole with a hammer;
• When performing work, you must ensure that the products do not touch or are positioned crookedly;
• when the cuff is installed all the way, you can proceed to screwing a self-tapping screw or a universal-type bolt;
• It is necessary to screw in the self-tapping screw using a screwdriver, adhering to the required depth.

Selection of building materials

In the manufacture of wooden mauerlat, beams are used. At the same time, experts advise making fastenings from deciduous trees treated with special antiseptic agents. The beams should be laid around the perimeter of the wall. To connect them together, specialists install a lock, which must be secured with nails. This will help make a strong, solid wood structure. It is important that its size be smaller than the width of the aerated concrete walls. The timber must be secured to the inner surface in such a way that there is a gap of five centimeters between the outer cut and the fastening. Sometimes builders use brick for a protective belt on the outside of the wall. Before starting installation work, waterproofing should be provided between the walls and beams.

Selection and features of fastening anchors for foam and aerated concrete

Which anchors are best to choose?

Anchors should be selected based on the weight that will fall on each individual fastener:

1. Anchors that can support up to 10 kg per fastener. Such products work mainly due to expansion and are a thickened plastic element that in working condition acquires a conical shape or expands inside the material. With their help you can hang small shelves, pictures, hangers, etc.

Anchors for fastening lightweight structures into aerated concrete

1. Anchors for a mass of 20-25 kg. These are fasteners of a special shape that allow the load inside the material to be distributed over the maximum possible area inside the base. They usually have a helical shape, significant length and diameter. They can be used to hang, for example, heating system radiators, kitchen cabinets, and façade cladding systems.

Anchors for fastening medium and heavy structures into aerated concrete

1. Chemical anchors for 30kg and more. They are special solutions supplied in tubes. Under them, a long hole of large diameter is drilled in the aerated concrete base, cleaned, filled with the compound and a metal pin is inserted. After hardening, the solution essentially turns into a solid capsule, comparable in strength to concrete. At the same time, it takes on the local load from the suspended structures and, due to its large surface area, more evenly transfers this load to the aerated concrete. This solution allows you to attach boilers and other heavy interior and exterior elements to walls made of foam block and gas block.

Chemical anchors for fastening heavy structures to aerated concrete

When choosing an anchor for aerated concrete, give preference to dimensional products with a large surface area. The longer and thicker the anchor, the better.

Practical recommendations for fastening into aerated concrete

Before fastening it into aerated concrete with your own hands, remember that:

• Installation of fasteners must be carried out with a minimum distance from each other of 10 cm. Otherwise, the overlap of stress areas in the gas block can lead to its collapse and the fall of the structure being fixed. The greater the spacing of the anchors relative to each other, the better and more reliable the fastening.
• The anchor should not be attached close to the edge of the block; the minimum offset here is also 10 cm.
• As already noted, the class of aerated concrete largely determines its ability to withstand the fastening of massive structures. For example, a B2.5 class block will withstand approximately 2 times less weight compared to B5.0, although the latter is used extremely rarely in low-rise construction.
• Despite everything described above, it cannot be said that this or that fastening to aerated concrete can be considered 100% reliable. The material is fragile, and it will be better if heavy objects are secured through a specially mounted metal frame, rigidly fixed to the concrete floor and/or ceiling. At the same time, to save space, the frame can be “drowned” into easily chipped aerated concrete.
• It is necessary to drill holes in the gas block for anchors in the drilling mode without impact. The drill should be selected 1-2 mm smaller than the diameter of the dowel, so that after driving, the fastener “sits” tightly in the hole.

Video on the use of Fisher chemical anchors in walls made of various materials.

So, we figured out how and with what help you can attach to aerated concrete and foam concrete blocks. You can find out how to attach to other building materials in our next articles.

Fixing the Mauerlat using wire

Before attaching the Mauerlat to aerated concrete using steel wire, it must first be fixed in the thickness of the wall. This should be done while laying the last rows of gas blocks - the wire is placed under them.

The installation technique in this way looks like this:

1. A couple of rows before the end of the masonry, a twisted wire of several thinner wires with a cross-section of 6 mm is placed between the blocks.
2. In this case, the central piece of wire will be placed in the thickness of the masonry, and the ends will hang down on both sides of the masonry. The length of the ends is made such that they are enough to wrap freely around the beam.
3. There should be so many pieces of wire that it is enough to tie all the rafter legs.

Feasibility of application

Chemical injection compositions and ampoules are expensive, their purchase is advisable when working with hollow and porous types of concrete; in dense structures they are justified when installed near the edge or in the case of increased expected loads: tensile, vibration, weight. Anchors of this type can withstand the weight of steel elements, consoles, columns, facade systems, equipment, fences, and, if necessary, they are used for additional fastening of reinforcing bars. When choosing this option, the quality of the base material has virtually no effect on the reliability of the fixation; the products of Hilti, Fischer and their analogues are designed for use in concrete with cracks.

They are also advised to buy:

• In the absence of an accurate calculation of the hole size.
• At high seismic and vibration loads on the object.
• If necessary, violation of the recommended intervals: placement along the edge of the structure or next to an adjacent anchor. Unlike standard dowels for concrete, they do not have a thrust force.
• For use in conditions of high humidity (the chemical composition reliably protects metal fasteners for concrete from corrosion).
• For installation in fire protection systems, the fire resistance of specialized types reaches 2 hours.