The trend to build houses from aerated concrete blocks is gaining popularity today. This material is becoming more and more in demand both in the construction of residential and commercial buildings. Demand for gas blocks is increasing for many reasons. One of them is the large size of building elements. In addition, the blocks have a clear geometry. Thanks to the use of an optimized adhesive mixture, it is possible to build a house with the most even walls in a short time.
The walls at the same time have a small mass, which reduces the load on the foundation. The thermal insulation properties of aerated concrete also turn out to be quite good. This reduces the cost of insulation. Mounting a Mauerlat without an armored belt has many subtleties that should be considered before installation.
Why do you need a Mauerlat
Mauerlat is the supporting part of the rafter system. In terms of functionality, it is comparable to the tape of the base of the house. She is responsible for the loads that are transmitted from the entire building, and only the rafter system and the roofing cake affect the Mauerlat.
The loads on the Mauerlat can be significant. They differ in bursting orientation, which is perpendicular to the walls. This means that if the rafter system is not designed correctly, the walls can collapse. Point loads, which are transferred to walls from rafters, are of increased danger for structures made of piece materials (which include aerated concrete).
Mauerlat takes the load from the rafter legs onto itself, evenly distributing the weight of the roof along the perimeter of the walls. The second distinguishing feature of the Mauerlat is to facilitate the installation of rafters. These Mauerlat capabilities are only a small part of its functionality.
As a material, a bar with a section of 100x100 mm is chosen. Often, builders follow the unspoken rule - the Mauerlat should be as thick as two rafters. The width of the beam is chosen taking into account the thickness of each wall.
Mauerlat is laid in such a way that it is not flush with the wall, both from the outside and from the inside. This eliminates the harmful effects of external factors on wood. This rule is not necessary to follow, however, many craftsmen leave about 5 cm from each edge.
When choosing logs for Mauerlat, you may encounter difficulties mounting it on the wall. For such work, it is worth inviting an experienced carpenter. Since the Mauerlat is a critical element of the building, you should choose a first-class tree for it.
It is better to pay attention to hardwood. However, such material is not easy to find. Therefore, many use ordinary high quality pine. Mauerlat is made not only from wood. For example, if you plan to create a rafter system from metal trusses, you should choose a steel beam for the Mauerlat. In practice, they usually still choose the traditional option - a tree.
If during the construction of brick walls it is possible to create wooden bookmarks, then in the case of aerated concrete this option is not suitable. On aerated concrete walls, a Mauerlat should be installed in a "closed circuit". It turns out a kind of frame that completely encircles the entire perimeter of the building.
Mauerlat mounting options
Before building a house from gas silicate blocks, it is worth deciding whether it is really impossible to reinforce the walls with an armored belt before installing the Mauerlat. The very option of installing a Mauerlat without reinforcement is accepted by builders with a number of reservations.
There are many conditions that will need to be met with this option for installing a Mauerlat without an armored belt:
- If the building is small.
- The roof has a simple structure and low weight.
- If the weather conditions do not imply a significant wind and snow load.
- In the case of a minimum opening force from the truss system.
The rafters on the Mauerlat must be securely fastened with puffs. In the case of layered rafters, a hinged or sliding fastening is performed. Such conditions are necessary when creating a Mauerlat without an armored belt.
Mauerlat fastening to wire
One of the popular options, due to its simplicity, is the installation of a Mauerlat, which is attached with wire. It is often used when creating brickwork. When choosing this option, 4/5 before the end of the masonry, steel wire should be laid between the rows. It should have a diameter of 3-4 mm. For each bundle, 4 cores are selected.
As a result of laying the wire, the bundles look out from the outer and inner sides of the wall. They are released to such a length that coverage of the Mauerlat installed on the timber is ensured. This will allow you to make a reliable tightening of the wire.
When the wall is ready, waterproofing material should be laid on it. After that, a Mauerlat is mounted from above, it is aligned, a wire knot is created and tightened. The tightening is carried out with a crowbar in order to press the Mauerlat more tightly against the wall.
Usually this method is used for brick walls. However, it is also applicable to houses made of gas silicate. Only in this case, the bookmark is mounted two blocks before the final row. However, many builders question this option for installing a Mauerlat, citing its unreliability. Perhaps, with strong wind loads and vibration, the wire will cut gas silicate blocks. After all, they are easy to process with a simple hacksaw.
Fastening the timber to the anchor and dowel
One of the easy ways to fix a beam to a wall without an armored belt is to install it on dowels or anchors. However, it is of little use for gas silicate. Considering that the material has increased brittleness, one should be prepared for the appearance of a crack or chip when tightening the fastener. This indicates the need for the correct selection of connecting parts.
Today, consumers are provided with a large selection of fasteners that are designed for aerated concrete. However, the difference in fastening furniture and Mauerlat to the walls of the armored belt is obvious. Since the beam is the supporting element of the truss system, it is important to approach its installation thoroughly.
The holding properties of gas silicate blocks are insignificant, therefore, you should choose anchors of great length - from 30 to 50 cm. This will allow, taking into account the thickness of the Mauerlat, to securely fix it on the wall. However, these anchors are relatively expensive. This should also be taken into account.
Install the Mauerlat on the wall without an armored belt in the following sequence:
This connection is ideal for concrete walls. In the case of gas silicate, even with long anchors, this method of attaching the Mauerlat without an armored belt remains in question.
Often the beam does not have sufficient length to lay it on the entire wall without armored belt in one element. In this case, resort to splicing several segments. Experienced carpenters can create reliable lock-type joints. However, for a professional, it is enough to make a half-tree connecting node. Be sure to install fasteners. Usually choose anchors or studs.
Similar is the fastening at the corners, in which the beams of adjacent walls are joined without an armored belt. For them, a locking connection with a tightening of a certain type of fastener is chosen. In addition, it will be possible to connect all the elements of the Mauerlat into a rigid base for the truss system using brackets.
Chemical anchors
A decade ago, few people knew about this method of installing a load-bearing beam on a wall without an armored belt. Today, everyone can buy chemical anchors. However, their cost is still high. Often, when building a house from gas silicate, epoxy with a hardener is used instead of chemical anchors. After that, fasteners are placed in the hole. After a day, the fastening is obtained as strong as possible.
Everyone knows about epoxy glue - it can also be considered a chemical anchor. However, the time during which the composition solidifies is quite long. There are several types of chemical anchors. One of them is the ampoule layout. An ampoule containing an adhesive composition is inserted into the hole. It may contain one or two components, and hardens fairly quickly on contact with air. After mounting the ampoule, a pin is placed directly in the hole and driven to the desired depth.
In the process of clogging, the ampoule is destroyed, and the resulting composition fills the channel. It also falls between the threads of the fastener, which ensures high reliability of the connection. At a positive temperature, after half an hour the composition completely hardens. In this case, the anchor will hold even under high load.
Another type of chemical anchors are polymer tubes sold with a gun. This device is similar to those commonly used when working with liquid nails.
Advantages of chemical anchors when installing Mauerlat:
- The mount will last for many decades - up to 50 years.
- The polymer is not affected by chemicals, atmospheric phenomena and biological factors.
- When installing such anchors, there is no bursting load inside the wall elements.
- Since the composite fills the pores of the material, the Mauerlat can be installed as firmly and reliably as possible.
Such fasteners also have several disadvantages:
- Chemical dowels are quite expensive, so installing a Mauerlat will be very costly.
- Chemical anchors are not very resistant to high temperatures. However, this minus can be called into question - the beam is unlikely to be heated to 100 degrees.
- There is no reliable information about the service life of chemical fasteners.
There is another way to attach the Mauerlat to the walls of a house without an armored belt - by means of embedded studs. They are placed in holes drilled in aerated concrete, filled with masonry mortar.
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.
Foam concrete blocks are an excellent choice for construction work. They combine structural functions and thermal insulation capabilities. But the presence of pores in the material gives the blocks a difference from dense bricks or durable concrete. Because of this, many have a question - how to fix the roof to the walls of the foam block. Let's try to understand the existing ways of performing this building unit.
Roof types
For the construction of roofs on foam blocks, all known options are used. Perhaps they are divided into two types - flat and pitched.
There are no problems with the first option. Floor slabs are laid on the walls, a roofing cake is arranged. The load effect is evenly distributed over all walls.
The blocks on which the roof rests will be in the same conditions if the masonry of the walls were erected further, and the upper floors would press on them.
There are more options for pitched roofs:
- lean-to;
- gable;
- attic;
- hip or four-slope;
- pullovalm.
There are more complex unclassified forms. But this is not so important, because they imply a truss structure that supports the ceiling.
The load impacts from the rafter legs, if they are fastened directly to the walls, will be point-like, for this reason, problems are created in arranging the roof fasteners to the foam block material. But first you need to deal with the features of the truss systems.
It is already clear that the main detail is the rafters connected by the crate and holding the roof. They are divided into two groups:
- inclined - supported by both ends on the wall, racks or Mauerlats;
- hanging - based only on the lower ends, and the upper ones hang freely. In combination with other elements, they can form a farm.
Installation
Let's deal with the sequence of work.
If there is an armored belt
With its presence, the design is reliable.
The monolithic belt is represented by a band of reinforced concrete material located along the upper perimeter of the walls. It can be arranged in blocks and other piece materials.
The main purpose is to tie the masonry and distribute the load evenly on all existing walls. Arranged on cellular concrete, it creates additional surface protection from punching.
Monolithic reinforcement can be done in the formwork structure, but most often block rows are laid on both sides of the wall to create a tray. Reinforcement is installed inside, which is then poured with concrete mixture.
Filling the belt somewhat complicates the overall design of the object, but gives it reliability and makes it more durable. The cost of the work increases, but not significantly, because much steel material and concrete mortar are not required.
If a large object is being built, or a heavy roof is expected, then the device of a reinforced belt is considered mandatory.
Mauerlat on the foam block can not be arranged, the rafters to the armored belt will be fixed without it. But it would be better if this element is present, since the fastener is inserted into the wood more easily.
How to fix the Mauerlat to the foam block? The element is mounted in two ways:
- At the time of pouring the concrete mixture, anchors are laid. For them, holes are drilled in the Mauerlat to be pulled to the concrete with nuts. The method is reliable, but it involves the exact marking of the centers of the holes.
- The Mauerlat is drilled under the studs after it is laid on concrete. The drill must go through wood and concrete. The studs are additionally fixed with an adhesive, or you will have to use expansion type anchors.
It should be noted that a waterproofing layer is necessarily arranged between the wall and the Mauerlat.
Now in the rafter legs it is necessary to choose the angle with which they rest against the Mauerlat, as an addition, corners can be set along the edges. Some Mauerlat masters choose a groove to create a more secure fastening and eliminate the likelihood that they will move along the wall when the corner is destroyed.
Those who wish can tie the Mauerlat and the rafter leg with wire, which is also allowed.
A support bar is reinforced with steel plates on the rafters, with which it rests against the Mauerlat bar. Additionally, a metal square is strengthened along the entire surface, for which transverse grooves are selected in the rafters. You can fix such an emphasis not with a metal plate, but with two more bars, which will create an additional emphasis.
On the end section of each rafter leg, you can arrange a recess in the form of the letter "V", with which it rests against the Mauerlat. But in this case, the rafter will not go beyond the wall.
It should be remembered that foam concrete easily absorbs water. For this reason, it is recommended to make decent roof overhangs, which means the release of rafter legs.
As an addition, you can use clamps made of wire, metal tape and other material. They cover the rafter, attracted to the bottom. The clamp is fixed with dowels to the inner surface of the wall. Such a measure is good when it is necessary to create an additional margin of safety for the connection of the roof and wall.
Without armored belt
How to fix the roof to the foam block in this case?
It should be noted here that this method is easier - roofing parts are laid on the surface of the walls. This option is good for outbuildings built on their own.
When performing a roofing installation, special attention should be paid to the Mauerlat. Without it, fastening rafters to foam block walls is not recommended. The element will evenly divide the load forces on the walls, its width should be equal to the size of the wall.
The Mauerlat is fixed to the block masonry with dowels or studs. It is best to plant them on a mortar mass or glue them. The diameter of the fasteners must be at least three centimeters so that loosening does not occur.
When the racks or the upper ends of the inclined rafter legs rest on a partition made of foam block material, then it is necessary to lay a run on top that distributes the load over the entire available area.
If the hanging rafters do not have puffs, then they will “spread” in different directions, and the only obstacle to this will be only the wall. If it is from a foam block, then the mounting studs will begin to loosen from the load. Therefore, puffs are considered mandatory, and it is better not to raise the type.
The same reason does not allow installing a mansard type of roof, the lateral rafter legs of which transfer the load horizontally. But such restrictions can be circumvented by arranging additional fastenings of the rafters, brought out beyond the dimensions of the walls to the floor beams, which act as puffs.
Conclusion
Probably, it became clear how to make a shed roof on a foam block or another, more complex roof structure. Remember that over the entire surface of the block masonry, a wooden beam should be placed - Mauerlat, which will take on all the loads from the ceiling and distribute them in equal shares to the walls. With the help of such an element, you can mount the roof of any economic facility and even a residential building with your own hands, if you feel confident.
Mauerlat is a rectangular wooden beam laid along the entire length of the upper cut of the external building envelope of the house. It is designed to fasten the truss system and evenly distribute the load from the roof to the walls and foundation of the building. Reliable fastening of the Mauerlat to aerated concrete is the key to successful operation and durability of the structure.
How to fix the Mauerlat correctly.
The functional purpose of the Mauerlat
Heavy rain, gusts of wind, a layer of snow - all this creates additional loads on the frame of the building.
The presence of a Mauerlat in the roof structure makes it possible to simplify installation work on the arrangement of the coating and protect the load-bearing elements of the structure from additional loads.
Beams, laid around the entire perimeter of the building in conjunction with the rafters, provide a stable and durable structure that serves as the basis for any roofing.
Mauerlat keeps the truss system from moving.
Mauerlat is made of coniferous wood, except when the roof lathing is made of metal structures. Then steel profiles (corner, channel, etc.) are used for tying the outer walls.
In addition to its main purpose - fixing the roof and distributing the load on the building frame - the strapping can serve as a monolithic belt. During the construction of a one-story house, it is allowed to install a beam along the inner edge of the wall directly on aerated concrete blocks, without an armored belt. In this situation, the mauerlat also serves as the main connecting element for external building envelopes.
Selection of material and calculation of parameters
When choosing a material, you need to pay attention to the structure of the tree, the absence of distortions and the integrity of the surface. Products must be free of knots, cracks and traces of biological impact. The moisture content of the purchased wood should not exceed 8%.
Mauerlat is made of a wooden rectangular profile with a size of:
- 80 x 180 mm;
- 100 x 150 mm;
- 100 x 100 mm;
- 150 x 150 mm;
- 200 x 200 mm.
The following factors influence the choice of the beam section:
- number of storeys and external dimensions of the building;
- design features (the number of slopes, the presence of an attic, etc.);
- roofing material;
- climatic conditions of the region.
The thickness of the Mauerlat must correspond to the recommended loads - excess weight of the product will affect the bearing capacity of the foundation.
Dimensions of wooden beams.
The calculation of the mass of the timber used is as follows:
- Determine the cross-sectional area - multiply the width by the height.
- Multiply the resulting value by the perimeter - we get 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 outer 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, therefore, for a distance of 8 m, you need to purchase 2 segments of 6 m each.
When choosing a profile height, it must be taken into account that the rafters are connected to the Mauerlat by cutting, using 50% of its actual size.
Varieties of fastening
Installation of the support beam in the roof structure is carried out using anchor bolts, steel dowels, wire clamps. In the corners of the building, the structure is fixed with corners, metal plates or forged brackets.
Docking of profiles is performed with an oblique or straight cut (lock). The second method is more productive - it provides good stability under vertical and lateral loads. The bars are fastened with bolted connections or self-tapping screws through a perforated metal profile. The device of connecting seams is not allowed in the places where the rafter legs are supported.
Mauerlat is placed in the center of the wall and 100-150 mm above the attic floor. Several layers of waterproofing material (roofing material, isol, etc.) are laid under the timber. Each section of the base must be connected to two adjacent sections with plates or forged brackets.
Mauerlat on aerated concrete without armored belt
Mounting the Mauerlat to the gas block without an armored belt can be done with all available devices:
- anchors (chemical and steel);
- wire clamps;
- metal studs;
- forged staples.
Mounting scheme without armored belt.
Installation of timber using anchors, mechanical or chemical, is possible only when building walls from solid blocks.
To fasten the Mauerlat with brackets, wooden plugs must be inserted into the masonry just above the ceiling. The staples are driven into the bars on the walls with one end, and driven into the middle of the supporting profile with the other.
Fastening with steel wire
The roof base can be fastened with wire clamps to the edges of the wall with or without an armored belt. In the first case, the blanks cling to the longitudinal reinforcement bars, in the second, they are inserted into the masonry. For the manufacture of connecting elements, annealed steel wire with a diameter of 4-6 mm is used.
The use of wire for fastening.
Details are installed around the entire perimeter of the building with an interval of 50-70 cm. The sections protruding above the beam should be at least 30-50 cm. After laying the mauerlat, the ends of the loops are tied together and with rotational movements with the help of a mount or crowbar they are tightly pressed against the profile.
Fastening with anchor bolts
Anchor bolts provide a strong connection between the structure and the base. They prevent the horizontal displacement of the profile, which contributes to the uniform transfer of the forces of the spread of the rafters to the enclosing structures.
To fasten the Mauerlat in the indicated way, holes are drilled in the masonry or armo-belt with a diameter slightly larger than the dimensions of the expansion element. Threaded couplings are inserted into them.
Samples are made in the body of the beam, coaxial with the holes in the belt. A profile is applied from above and the anchor bolts are passed through it. Tighten the connection with a wrench. Thus, the Mauerlat is attached to the base of the supporting structures.
An alternative to mechanical fastening is the adhesive mounting system. The anchor consists of a composite chemistry, a threaded metal rod, a washer and a nut.
Installation of fasteners begins with drilling conical or cylindrical holes in the body of the armored belt. Then, using a special tool for containers with injection mixtures, the solution is squeezed out into prepared samples.
Fastening with a chemical anchor.
Perform the installation of the Mauerlat. Through the timber, steel studs are inserted through and through.
After the adhesive composition has hardened (30-40 minutes), the assembly is ready for operation: washers are put on the rods, nuts are screwed on and the Mauerlat is compacted around the entire perimeter of the building.
In order to increase the strength of the connection, metal or polymer threaded couplings can be used with steel studs.
Arrangement of a reinforcing belt
A monolithic reinforced belt serves not only to fasten the mauerlat and distribute the load of the roof, but also to tighten the structure of the outer walls into a single fixed system.
For aerated concrete walls, the reinforcement belt can be made in two ways:
- The classic version with the manufacture and installation of formwork panels.
- Using U-shaped building blocks.
For the device of the armored belt, you will need the following set of materials:
- edged board;
- bars 40 x 40 mm;
- nails 70-100 mm long;
- self-tapping screws 3.5 x 70 mm;
- U-shaped blocks;
- rod reinforcement AIII, diameter 10-12 mm;
- smooth fittings V-1, Vr-1, Ø 3-6 mm;
- knitting wire - 0.5-2.2 mm;
- concrete class B15-B20.
Tools:
Fastening of beams to the armored belt.
- hacksaw;
- hammer;
- screwdriver;
- hook for knitting reinforcement;
- bending machine;
- vibrator for concrete compaction;
- construction roulette.
Formwork is installed along the entire perimeter of the load-bearing walls, the panels of which are attached to the outer and inner surfaces of the enclosing structures and connected together using bars, steel pins and annealed wire.
A reinforcing cage is placed in the formwork, a concrete mixture is poured inside and compacted with vibrators. In this sequence, the device of a monolithic belt is performed.
Formwork manufacturing
Formwork panels are made of boards 25 mm thick on a wooden frame of 40 x 40 mm bars.
The height of the products is taken equal and can be 250-350 mm, taking into account the overlap on the walls of the building. The length of the sections depends on the installation conditions of the structures (2-2.5 m).
Execution sequence:
- Cutting boards to size.
- Marking and sawing timber for the frame and lintels.
- Shield manufacturing.
- Preparation of clamps, studs.
- Pre-assembly of boxes on a flat area.
- Lifting sections and installation on the upper cut of the masonry.
- Fastening shields with jumpers.
- Docking of individual segments around the entire perimeter of the building.
If the project provides for the construction of a monolithic belt of standard aerated concrete products, then the last row of masonry is performed using U-shaped blocks.
The reinforcing cage for a monolithic belt is made of hot-rolled steel rods of class A-III with a diameter of 8-12 mm. Docking of the segments is carried out using a knitting wire Ø 0.5-2.2 mm. Clamps for assembling the frame are made of wire B-I and Bp-I.
The assembly of structures is carried out on special tables or on a flat area using stops.
Metal frame production:
- With the help of a bending machine, clamps for metal longitudinal rods are prepared from smooth reinforcement. The ends of the parts are pulled together with a knitting wire.
- From segments 0.8-1.2 m long, rotary connecting elements are made for joining the rods at the corners of the building.
- Then they take 4 rods and thread them into vertically mounted clamps. They are distributed at the corners of the frame and pulled together with wire.
- The assembly of the structure starts from the center of the segment, gradually moving towards the ends of the section.
Reinforcement of the armored belt under the Mauerlat.
Finished elements are lifted onto the walls and placed in the formwork. The reinforcing cage must be attached to the base in such a way that a distance of 25-50 mm remains between the wooden shield and the steel rod. Offset from the central axis of the outer wall is allowed no more than 10 mm.
After reinforcement, the formwork panels are strengthened, the vertical and horizontal level of the structure is checked, and they are prepared to receive the concrete mix.
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 with reinforcing bars using a knitting wire.
Fastening with metal pins.
If it is planned to lay a power plate without a monolithic belt, then a metal plate 1.8-3.0 mm thick and 100 x 100 mm in size is welded to the bottom of the part. At a depth of 40-60 mm, fixtures are embedded in the masonry. At the end of the installation, the upper part of the rod should rise above the surface of the beam by 3-5 cm.
The installation of studs in 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 fasteners are installed.
A Mauerlat is lowered onto the prepared structure and pressed in to make marks for the holes with studs. The beam is drilled, and when all the samples are ready, they string the profile onto the rods, throw washers and nuts on. Check the level of the bed and tighten the connections.
The number of studs under the Mauerlat must correspond to the number of rafter legs in the roof structure.
The importance of waterproofing during installation
Wood and aerated concrete blocks absorb moisture well, therefore, when preparing wooden products, it is necessary to treat them with hydrophobic compounds, followed by drying in natural conditions.
Before laying the Mauerlat, it is necessary to lay 2 layers of roofing material or isol along the monolithic belt and only after that install the elements. The durability of the installed structures, including the truss system and roofing, depends on the correct implementation of waterproofing work.
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.
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