Mauerlat is a special belt laid around the perimeter of the upper end of the external load-bearing wall of the building and intended for attaching rafter legs. Wood is considered a traditional material for the manufacture of this element of the rafter system, but if a metal frame is installed under the roof, then rolled metal - I-beams, channels or profiles - can also be installed as a Mauerlat.
DIY Mauerlat for a gable roof
It is relatively easy to install a Mauerlat for a gable roof with your own hands - there are several different technologies for this. But it should be remembered that the more securely it is fixed to the wall, the longer the service life of the entire structure of the rafter system will become.
Choice of material and its features
As a rule, a wooden beam, an I-beam, a channel or other various metal products are used for production:
- Wooden beam . When using timber for the Mauerlat, the section dimensions should be as follows: 100×100 mm, 100×150 mm, 80×180 mm, 150×150 mm or 200×200 mm. When laying it, it is placed around the perimeter of the walls. The main factor in choosing timber will be the absence of knots, since the Mauerlat works in tension, and if there is a knot, a break may occur at this place.
- From bonded boards . If the roof is very light, without insulation and has a small area, you can use two nailed together boards of the same cross-section.
- Steel pipes . Often, when organizing a Mauerlat, beams made of steel pipes are used. They are a frame that does not protrude beyond the perimeter of the wall.
Such pipes work very well in bending, and round holes do not reduce the strength of the wooden rafters themselves. The main advantage is that the wooden Mauerlat is hidden under the roof and is not affected by snow, moisture and other factors.
Video description
The video shows the technology of attaching the Mauerlat to the wall of a building using anchors:
Chemical anchors
Just recently, no one knew about this fastening technology. Although many craftsmen know how to secure any steel pin using epoxy. The technology is the same here, but instead of epoxy resin with a fixer, other ready-made compounds are used.
One of the methods is called capsule or apmul technology. This is a capsule in which the adhesive composition is sealed. It is driven into the prepared hole, where a pin is driven from above. The first one bursts, the glue spreads inside between the walls of the hole and the thread of the stud. After polymerization, which can take up to 45 minutes, a very strong mount is obtained.
The second option is a two-component composition in cans. A pistol nozzle is put on the latter, with the help of which the composition is fed into the drilled hole. The composition is a polymer mass, quite viscous. Therefore, the anchor will have to be screwed into the filled hole, rather than driven in.
Chemical plug-in ampoule Source homius.ru
Installation and assembly of the structure
To allow air ventilation in the roof space and prevent rotting of the roof elements, the top of the Mauerlat is placed on the wall with a distance of 300 millimeters from the edge of the ceiling.
There are two main ways to install and assemble this structure:
- The mauerlat bars are connected into a single box along the entire length of the external walls of the building. They are connected by an oblique cut, secured with bolts, nails or self-tapping screws. And the corners are additionally pressed with plates or metal corners. As a result, such a rigid frame, running along the entire perimeter of the house, accepts the expansion and compensates for the stretching and bending of the rafter system.
- Along the entire perimeter of the wall, a concrete belt with a protrusion for the anchor is poured. This method is only relevant for walls made of foam concrete blocks and similar materials. The beams, pulled by anchors, distribute the vertical load and lower the thrust to the base of the building.
Installation without reinforced belt
With this method, the rafters are attached directly to the floor beams. Only if the walls and beams have a sufficient level of reliability. The work is carried out in the following order:
- To erect the roof you will need timber and edged boards.
- The timber is laid out under the beams along the perimeter of the roof. The timber is chosen with a cross-section of 50×150 millimeters.
- To protect the wood from moisture, waterproofing is done with roofing felt.
- The roofing material is bent to the required length and cut.
- Beams are installed at the required distance from the edge of the wall.
- Roofing felt is laid around the beam and secured with a furniture stapler.
Creating a reinforced belt
The most difficult thing about making it yourself is erecting a mauerlat on walls made of aerated concrete. It is recommended to make a brick or concrete structure on top of foam concrete, since the Mauerlat requires a dense base.
To create a solid foundation to avoid pushing through and destroying the walls with timber, a reinforced concrete strapping belt is constructed. It consists of a concrete strip measuring 200 by 150 millimeters. The main factor for correct installation is the calculation of the number and location of stud installation sites, while the number of rafters and fasteners must be equal.
The thickness of the belt is calculated based on the load exerted by the roof, the weight of the rafter system and the roofing material.
The main material of the tape is M400 cement, pouring is done in one layer. The composition of the solution should be in proportions 1: 3: 3, cement, sand and crushed stone. Additionally, you can add various plasticizers to the solution to reduce the percentage of water in the composition.
Assembly and selection of material for formwork
The main thing at this stage is that the armored belt is solid. Formwork can be constructed from OSB boards and edged boards. Throughout the entire work process, the horizontal installation of the formwork is controlled.
Selection of fasteners
On frame walls made of logs, the mauerlat is attached with self-tapping screws or ordinary nails. For better contact, perforated tapes are used.
If the roof has an area of more than 250 square meters, then the Mauerlat is attached only to studs, in increments of 150 centimeters along the perimeter of the wall. First, the concrete screed is poured, and then the studs are installed into it. In this case, their height should be greater than the height of the beam, with a margin of 30 millimeters.
Concrete pouring work
The thickness of concrete pouring must be at least 50 millimeters. As soon as the layer is filled, make sure that no air cavities are formed; they can be detected by the emerging bubbles. Such cavities are dangerous because they reduce the strength of the structure.
The formwork can be dismantled 12 days after pouring, when the solution has completely set.
Laying waterproofing materials
Mauerlat without waterproofing will not last long; over time it will become damp and begin to rot. To prevent this process, you need to waterproof it with roofing felt. Laying is done with a tape slightly wider than the beam, the main thing is to prevent the material from tearing during the work in the places of the holes for the studs.
What it is
Mauerlat (from the German words Mauer - “wall” and Latte - “beam”, literally “beam on the wall”) is a part of the roofing structure (usually a beam) laid along the upper end of the walls on which the rafters rest, or along the entire perimeter .
Mauerlat performs 2 main functions:
- Transfer by linking part of the load from the roof to the supporting structures of the building.
- Uniform distribution of this mechanical load along the entire length of the walls on which it is mounted, or along the entire perimeter of load-bearing structures.
In addition, it, as an additional connecting element, increases the stability and rigidity of the rafter system.
Options for fastening the rafter system
As mentioned above, the main task of installing a power plate is to distribute the load. Therefore, you also need to pay special attention to the fastenings of the rafters, as they transfer the load to it. It depends on this whether the roof will shift or subsidence over time. And this can happen if one of the rafter legs creates a stronger load than the one standing next to it.
There are two methods for tying rafters to timber:
- Tough. When using this method, any possible displacement of the rafters, bends or shifts is eliminated. For a more stable installation, a hemming block is used, which will not allow the rafter leg to move. And metal corners will prevent the rafters from moving horizontally. In most cases, ordinary wooden boards are used for rafters, but their disadvantage is that they absorb moisture and swell quickly. It is very important to secure them to the Mauerlat to prevent the formation of a thrust force, which can reduce the service life and reliability of the structure. To do this, the saddle of the cutout at the end of the rafter leg rests against the Mauerlat and is firmly secured with nails driven at an angle. The cutouts on the rafters must be strictly identical and not exceed one third of the width of the rafters.
- Sliding. This fastening is used if the main frame of the building was made of logs or timber, which during the first time after laying give rise to sediment due to the drying of the wall material. In this case, the Mauerlat is no longer used; its role is played by the upper crown of the wall. To compensate for the movement of the log house without harm to the roof, sliding angles are used, which allow you to change the height of the rafter leg attachment. This type of fastening is also called hinged. Depending on the type of wall material, they all have different shrinkage rates. Glued laminated timber sags the least, and most of all fresh rounded logs, which during the drying process can lose up to 15% of their height, which will further skew the roofing system. Roof misalignment can also occur during the operation of the building, for example, during periods of high humidity; during prolonged rains, the wood swells greatly, and in winter it loses most of its moisture. Moreover, different parts of the walls and sides, depending on their location, have different shrinkage coefficients. Over the entire period, the technical and dimensional parameters of the log house are constantly changing. And interior walls are no exception, especially in winter, when a large temperature difference is recorded.
How to correctly calculate the parameters of the support beam
The Mauerlat is one of the strength elements of the rafter system, so it must be made from a powerful wooden beam or thick board. When determining the size of the mother beams, experienced builders are guided by the dimensions of the external walls - the transverse dimensions of the elements of the rafter belt should not be less than a third of their thickness . In most cases, these conditions are met by wooden beams with dimensions from 80x150 mm to 200x200 mm. The principle “the thicker the better” does not apply here, because excessively thick beams place an increased load on the walls and require additional effort during lifting and installation.
For the sake of economy, as well as for light loads, for the construction of the Mauerlat, you can use not a solid wooden beam, but fastened boards.
The length of the beam must correspond to the wall of the building. If the wooden frame cannot be made from solid beams, then they are joined. It is important that the individual parts of the straight sections are as long as possible. So, when using lumber of a standard length of 6 m on an 8-meter wall, you should take two beams 4 m long.
The dimensions of the Mauerlat belt are determined based on the length of the walls and their thickness
The connection is made with an oblique cut or the “half-tree” method with a straight or beveled lock. The first method is preferable because it provides higher rigidity under vertical loads. To fasten two parts of a beam, a bolted connection is most often used, less often - nails or powerful self-tapping screws.
In order to calculate the load that the Mauerlat will exert on the walls, use the simplest formulas to determine the weight and volume m=ρ×V and V=S×L, where m and V are the mass and volume of the Mauerlat, ρ is the density of wood, and S and L are the cross-sectional area of the beam and its length. When making calculations, all dimensions should be reduced to one system of units.
Basic installation details
The Mauerlat beam should be laid no further than 50 millimeters from the outer edge of the wall. In the case of a gable roof, the timber must be laid parallel to the ridge of the roof, along the entire axis of the wall on the load-bearing walls of the house.
But also when installing it, it is important to ensure that the timber is laid horizontally, using a building level. If a deviation occurs, measures must be immediately taken to eliminate this deficiency.
The timber under the Mauerlat needs to be prepared, treated with an antiseptic and a fire retardant. Before fastening, lay the beam in its place and mark where the holes will be located. Individual sections of timber must be connected with a straight lock, additionally secured with nails. And also additionally securing it at the corners with a straight lock or an oblique cut. The Mauerlat can be attached to the boards using corners or metal brackets. Tighten all threaded connections using locknuts or with a groover backing and washer, and trim the excess length of the stud with a grinder.
The cross-section and fastening of the Mauerlat are not defined in GOST
To determine the parameters or check whether the selected section is sufficient for your purposes, you can refer to the standards that determine the dimensions of lumber from different types of wood for the national economy. However, the tolerances for the Mauerlat are not defined in GOST; any can be used, based on construction experience.
In other words, the choice of cross-section, wood and fastening is made for practical reasons, the location of the house, as well as other raw materials, for example, boards for sheathing. If your region has relatively low wind loads and there are no tensile strength requirements, you can rely on natural rigidity and fasten the frame without a lock. This is exactly how many construction crews do their work.
Waterproofing under the Mauerlat
If you plan to have a rather heavy attic structure covered with boards with insulation, laying a reinforcing belt under 5 rows of bricks and fixing the beam with rail anchor bolts will help securely fasten it. It is recommended for large houses to use premium quality hardwood, type 200*200. This design is used in regions where there are frequent gusty winds, and is applicable in mountainous and northern regions.
Mauerlat made of metal pipes
Typically, steel pipes are used for such cases. It is quite important that the steel is of high quality. There are several requirements described below:
- The cross-section should be small - since the pipe will be attached through the rafters. If it is larger than the hole, it simply will not fit.
- Durable steel - high-quality specimens ensure the success of the roof. The better the materials, the more time you can leave the roof undisturbed.
Useful tips
Filling the armored belt is required if the roof area is more than 250 m2. In some cases, however, you can replace it with a concrete beam. Studs are immediately inserted into this beam and placed vertically. The thread of the studs is usually M12. There must be a gap of at least 2 meters between the installation points of the studs; at the same time, they are also attached near the ends, so you can count from the corresponding points.
For medium-sized roofs, pouring the beam is not necessary. Its absence is fully compensated by the use of moderately long hairpins. When arranging the Mauerlat using wire rod, you must plaster it so that the wire does not spoil the appearance. This solution is suitable for roofs of limited size.
You can see one of the ways to attach the Mauerlat in the following video.
Required Tools
Having purchased all the materials, you need to stock up on tools that will help you in construction.
The list of tools includes the following devices and accessories:
- Construction knife;
- Saw;
- Hacksaw;
- Jigsaw;
- Axe;
- Chisel and hammer;
- Chisel;
- Level;
- Tape measure and square;
- Drill;
- Screwdriver.
Mauerlat connection along the length
This type of structure requires a large length of timber. Most often, you have to splice wooden blocks together.
There are several connection options:
- oblique cut The timber at the joints is sawn obliquely with ends 0.15 of the section height. The length of the connection should not be less than the height of the Mauerlat multiplied by two. The connection point is bolted through and through. This method is perfect for connecting the Mauerlat along the length;
- "in the paw." This method is suitable for corner joints. For one beam, the lower part of the joint is cut at a right angle, and for the second, the upper part is cut out. The connection point, as in the previous case, is tightened with a bolt. Right angles do not allow the Mauerlat to move.
