Correct fastening of rafters to the mauerlat. Supporting nodes for layered rafters on the purlin and mauerlat. Main elements of the rafter frame

The Mauerlat is considered an important element of the roof structure, since the roof actually rests on the support beam. It helps to distribute it evenly and rationally on the roof. The rafters are also attached to it.

Attaching the rafters to the mauerlat is a significant step in the construction of the roof. The strength and safety of the roof depends largely on the quality of installation of the rafter system, in particular on the right choice fastening elements and proper connection of the supporting structure units.

Attachment points for rafters to the Mauerlat

There are two ways to attach rafters to the Mauerlat:

Obviously, the technology for attaching the rafter leg to the support beam will determine its “behavior” in various weather conditions. For example, when there are temperature changes or snowfalls, the supporting structure cannot be static. Indeed, under conditions of high humidity, wood expands, and high temperature causes compression. If you use rigid fixation, there is a risk of displacement; even ruptures cannot be ruled out. Due to improper installation, a thrust force may appear, which poses a danger to the walls. Therefore, proper fastening of the rafters to the mauerlat is a certain guarantee of safety.

The following support units are distinguished:

Rafter leg mounting options

To perform the lower assembly of supporting the rafter leg on the support beam, one of the following methods is generally chosen:

Both of these options have the same right to life and are used taking into account the shape of the roof and the features of the rafter system.

Fastening methods with and without sawing

Let us immediately note that fastening the rafters to the mauerlat without cutting is used exclusively in the case of a sliding connection. To hold the lower edge of the rafter legs freely lying on the mauerlat, corners are usually used. Obviously, such a fixation may not withstand significant loads, so it is recommended to use it primarily when covering relatively small spans.

The device of the lower interface unit, which uses fasteners with a notch that locks the tooth, is considered much more reliable. It is cut into the rafter board. As a rule, it occupies no more than a quarter of the beam. You can do it in different ways:

Fasteners for rafters and rules for working with them

The modern construction market offers a wide range of fastening elements. In addition to the classic options - staples, twisted nails or rolled wire, which is folded in several rows, here you can find special kits designed for working with rafters.

Fastening work is carried out in a certain order. We present to your attention some of the most simple methods sawing and subsequent adjustment of rafters.

The rafter legs are fixed with one of the fastening options. It should be noted that each of them has its own subtleties. The choice is based on parameters such as the angle of inclination of the slopes and the optimal support unit.

After installing the lower rafter assembly, they proceed to its connection with the ridge beam.

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Basic methods of supporting rafters

There are several technologies for supporting rafters on the Mauerlat. The structure can be rigidly fixed. It does not allow any displacement of the rafter leg. To do this, you should use a hemming beam, which prevents the rafters from slipping at the point of support, and metal corners, which eliminate any lateral shift of the structure.

The sliding connection of the rafter leg is used in wooden houses. Moreover, the main element for its support is the upper crown, and not the Mauerlat. To prevent damage to the roof, the rafter support unit is made as free as possible. To do this, you should use a sliding support, which, when the log house shrinks, is displaced along a guide attached to the leg.

The sliding support unit can be made using a different technology. A notch is made in the rafters, which should be adjacent to the upper crown of the log house. To fix the beams, it is permissible to use any fastening elements: staples, nails or steel plates.

Fasteners for installation work

To qualitatively connect the rafter assemblies with the Mauerlat, you will need the following materials and tools:

dry timber;
boards;
axe;
hacksaw;
hammer;
roulette;
plumb line;
level;
screwdriver;
drill;
Bulgarian.

Particular attention should be paid to the presence of all fasteners. The beam consoles are fixed using galvanized steel beam brackets, which do not reduce the load-bearing capacity of the structure. There is no need to embed the brackets into the beams.

You also need to buy perforated mounting tape, which will strengthen the Mauerlat nodes. With its help, a strong connection of all structural elements is made. The tape also does not cut into the beams. To securely fix it, nails and screws are used.

In addition to brackets and perforated tape, to securely support the rafters to the mauerlat, you should purchase:

universal timber connectors;
fasteners for rafters;
embedded supports;
wire rod;
steel corners;
rack mounting;
self-tapping screws;
nails;
staples;
plates;
galvanized nails;
studs with washers and nuts;
anchor bolts.

Creating a ridge and installing the bottom of the rafters

Installation work begins from the ridge part of the roof structure. You can install rafters in one of three ways:

end-to-end;
for a run;
overlap

Joining a structure end-to-end involves cutting the upper part of the rafter leg. This is done at an angle that is equal to the slope of the roof slope. On a skate, a pair of legs is connected. To obtain the same support unit for the Mauerlat elements, you should use a ready-made template.

A special feature of fixing the rafters to the purlin is the presence of a ridge beam. This option for arranging the Mauerlat is characterized by increased reliability. But often such a rafter support system involves the installation of additional supporting structures, which will lead to a decrease in the functionality of the attic. Naturally, this method is not suitable for small roofs.

The technology for installing overlapping rafters is in many ways similar to installing them on a ridge girder. The main difference is that the upper part of the legs overlaps. This leads to a strong connection of the structure, since the studs hold two elements at once.

The connection of the lower ends of the rafters is carried out depending on the material of the walls. In the presence of wooden house construction, the upper frame of the wall can act as a supporting element. If foam blocks (or aerated concrete) were used during the construction of the house, then the rafters are supported on the mauerlat.

The construction of a reinforced concrete belt is the optimal solution when using masonry building materials. This technology does not provide for the creation of any methods of fixing the rafter system. Vertical anchor bolts serve as fastening elements for the timber. The main thing is that when pouring concrete mortar, the studs are located in a strictly vertical position.

Connection of rafters with beams and mauerlat

After fixing the top and bottom of the rafters, they should be secured to the beams. It is clear that you can connect the rafters to the beam simply with nails. But this is not the best solution. Such a mount will not be as reliable as possible. To prevent sliding of all elements, the truss structure is fixed to the beams by using “tenon” and “tooth” connections.

If there is a steep roof slope (more than 35º), cutting technology using one tooth is used. A tooth with a spike is made at the bottom of the rafter. The nests created in the beam must have a depth of 30% of the beam thickness. The installation of rafter connections is carried out at a distance of 0.3-0.4 m from the extreme part of the beam. This prevents the beams from chipping as a result of heavy loads from foot pressure.

When arranging a roof with a slope of up to 35º, the rafters are installed by expanding the interface area of the main structural elements. Usually the rafter leg is covered with a beam. For this purpose, holes are cut in the rafter leg for two teeth:

tenon with stop;
one more emphasis.

The cutting depth when fixing the rafters to the beam is within 30% of the thickness of the beam.

Better connections can be obtained by using bolts or clamps. This technology involves the use of wire loops, with the help of which the unit is fixed to anchor bolts located in the wall of the building.

Supporting the Mauerlat is the most common option for fixing the lower part of the rafters. A cutout is made in the rafter leg of such a size that it can be placed on the Mauerlat without any problems. Otherwise, during operation of the roof, the beam may shift.

In some cases, the Mauerlat must be “equipped” with a reverse notch. It depends on the type of wood from which the timber is made. If hardwood was used for its production, then a slot is made, which, in combination with the notch of the rafters, will create a locking element. When making timber from coniferous wood, a cutout is not required, as it will weaken the structure.

The most acceptable option for a Mauerlat is a rigid connection of the rafter system.

This technology can be performed in one of two ways:

using hemming bars and corners made of metal;
by installing saddles on the rafters.

The first option is to use a support beam to place the rafters on the mauerlat. The rafter leg is rigidly supported. Reliable fixation of the structure is carried out with metal corners. This prevents lateral movement of the structure.

The second option is more popular. For fastening, nails are used, which are directed towards each other and driven in at an angle. Two hammered nails cross. Then another nail is driven in. The third nail should be in a vertical position. The made fastening unit will be characterized by maximum rigidity if additional fastening is carried out using wire rod.

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Knots for supporting rafters on the mauerlat. How to attach beams to the mauerlat

Hinge joint with one degree of freedom implies the ability to rotate a wooden or metal beam in a circle. This property is possible when attaching the beam to the mauerlat using one screwed-in nail or self-tapping screw.
Hinge joint with two degrees of freedom allows the beam to rotate in a circle or move slightly in the horizontal direction. To give such freedom to the movement of the beams, you need to fasten the rafters to the mauerlat by installing a slide or securing the rafters with the usual fastening angles, creating a sliding support - a slider.
Hinge joint with three degrees of freedom ensures the movement of rafters in both vertical and horizontal directions; fastening the beam does not interfere with its circular rotation, as in the two previously listed degrees of freedom. To make such a fastening, it is necessary to make an exclusive hinge that will be screwed into the Mauerlat.

Node with zero degree of freedom- This is the most common method of fastening rafters in brick buildings. Both ends of the beam are firmly secured with construction angles and self-tapping screws on both sides. This method of fastening does not allow the beam to move.

This video shows one of the options for sliding rafter fastening to the Mauerlat.

Attaching the rafter leg to the mauerlat

Correct marking and calculation of the roof frame in the drawing, and then the quality implementation of the plan in the roof structure is of great importance. Every year, the roof of a building is regularly exposed to the risk of violating the integrity and even deformation of the adjacent walls, due to large amounts of precipitation, changing temperature conditions. In addition to external risk factors, the base of the roof and walls must withstand the considerable weight of the frame and coverings.

The multi-level roof frame consists of main load-bearing links: rafter legs and mauerlat. Their correct installation guarantees the durability of the roof, the exact location of all ceilings, and therefore the optimal functioning of protective sound insulation, waterproofing, and vapor barriers.

Of all the variety of varieties, we will consider gable roofs, because they are the ones who need a supporting base - a Mauerlat.

To create it, you need to use the material that is planned to be applied to all load-bearing and supporting elements of the frame. If the frame is completely wooden, then the bars for the Mauerlat should also be wooden.

Needs to be taken care of about the correct shape of the beams for the roof base. It is not advisable to use uneven beams with protruding knots. If you are unable to find even beams, make sure that the length of the small branches is not more than one third of the width of the beam. Ideally, all beams are processed and delivered to the roof assembly stage calibrated and milled on at least both sides, and preferably on all four sides.

For the roof frame, and therefore for the mauerlat, iron or reinforced concrete is often used. This frame is highly durable. If, according to your individual calculations, the walls will support the weight metal frame, you can select this option. For the metal frame, Mauerlat blocks of the same material are used.

The dimensions of the beams vary from ten centimeters, usually beams of at least fifteen centimeters are used. The width of the beam directly depends on the length and width of the rafters. For example, if the cross-section of a gable roof beam is 40x150 mm, then Mauerlat beams with a cross-section of 100x100 mm are used. With a timber section of 100x250 mm, a Mauerlat of 150x150 mm is made.

The Mauerlat is attached to the inside of the outer wall using anchors, steel wire or studs. In the process of laying the Mauerlat bars, you need to connect them at all joints with metal staples.

Mounting methods

How to attach rafters to the mauerlat? According to the method of attaching the rafters to the Mauerlat roof frames are divided into:

Layered rafter system.
Hanging rafter system.

Layered rafters are classified as non-thrust frame structures, which determines their minimum pressure on load-bearing walls. The support points for layered rafters are the external walls of the building and the vertical posts located in the middle of the roof frame on a pre-installed tie.

The rafters attached to the mauerlat are most often hinged. When using sliders and movable hinges in fastenings, the roof frame can lower by several centimeters. This is necessary for an architectural structure in the first years after construction. When temperature and weather conditions change, the new building shrinks slightly. If the roof does not change its position following the supporting walls, the elements of the building may undergo cracking or deformation, which will not happen due to the layered fastening of the rafters on movable hinges.

Hanging rafters

Hanging rafters are used for buildings that do not have load-bearing walls inside. The support points for hanging rafters are only the external load-bearing walls. The fasteners of such structures are represented by a unit with a zero degree of freedom. Other methods are not available, since fastening the rafters to the mauerlat on the walls is the only support for the entire roof structure.

Hanging rafters- These are spacer structures. Rafters secured in a hanging manner are only capable of exerting horizontal bursting pressure on the walls, but this pressure is very high.

To reduce pressure on beams and walls use crossbars- These are special puffs. They are installed perpendicular to the rafters, closer to the bottom of the structure and are securely attached to each beam, collecting parallel rafters into a single whole. Without crossbars, it is impractical to build a roof with hanging rafters.

Technologies for attaching a rafter leg to a mauerlat

The connection of the rafters to the mauerlat is made both with the help of cutting, tapping, and sawing, which usually occupy no more than 1/4 of the beam, and without them. Depending on the angle of the roof slopes and the use of the optimal support unit, the method of laying and fixing the beam on the mauerlat is selected.

The photo shows one of the methods of attaching rafters to the Mauerlat.

The elements are fastened using various devices:

self-tapping screws;
bolts with nuts;
corners;
varieties of corner KR;
plates;
wire ties;
perforated mounting tape TM;
WB brackets;
LK fasteners;

Installing rafters on the mauerlat- this is the fastening of the horizontal load-bearing surface of the roof with the vertical one. Proper calculation and installation of all elements of the frame system is important.

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The reliability of the roof structure directly depends on how correctly its entire supporting system is installed. And its main elements are rafters. The entire system consists of rafter legs that support and expand additional elements, such as struts, crossbars, side girders, support posts and braces. The rafter legs are connected on a ridge beam from above, and their lower edges very often rest on a mauerlat mounted on the side load-bearing walls of the building.

Since the Mauerlat bears the heaviest load, it is made of powerful timber. Its cross-section is determined by the massiveness of the entire rafter system, but generally the size ranges from 150 × 150 to 200 × 200 mm. This load-bearing element is designed to evenly distribute the load from the entire roof and roof structure onto the load-bearing walls of the building. The rafters are fastened to the mauerlat different ways. They are selected locally depending on the type of rafter system (which can be layered or suspended), its complexity and massiveness, and the magnitude of the total loads to which the entire roof structure will be subjected.

Types of connecting nodes “rafters - Mauerlat”

First of all, there are sliding and rigid fastenings of rafters to the Mauerlat.

1. Sliding mounts consist of two separate elements, one of which has the ability to move relative to the other.

These mounts can be of different designs - closed and removable.

A closed mount consists of an angle, which is attached on one side to the Mauerlat, and on the other side has a special slot-like eye. A metal loop with holes for fastening to the rafters is installed in it. Thanks to the free, unfastened vertical side of the corner, the fastening allows the rafters to move slightly if necessary, without exerting a deforming effect on the walls of the building.

The open fastening is designed according to the same principle, and differs only in that the metal loop is not inserted into the eye, but simply the upper part of the vertical shelf of the angle bends down after installation, thereby fixing the connection.

Video: example of installing a movable mount on a rafter leg and mauerlat

2. There are many more types of rigid fastenings. They are selected depending on the massiveness of the wooden structural elements and the method of installing the rafters on the mauerlat.

This includes metal corners different sizes, LK fasteners, which will securely fix the rafter installed using a saw, without damaging it with fastening screws or nails.

LK fasteners are produced in several sizes, so they can be selected to suit any thickness of the bar or board. The thickness of the metal from which these fasteners are made is 2 mm, no matter what size they are. Depending on the size, fasteners have different designations.

Designation	Size in mm
LK-1L	40×170
LK-2P	40×170
LK-3L	40×210
LK-4P	40×210
LK-5L	40×250
LK-6P	40×250

It should be noted that these fasteners are suitable not only for connecting rafters to the mauerlat - they are also used for fixing the “floor beam - mauerlat” assemblies.

The main advantage of this fastener is the maximum rigidity and reliability of the connection of wooden elements.

Fastening rafters with a cut to the Mauerlat using corners is carried out on both sides, which ensures the required rigidity.

There are corners designed for fastening rafters without cuts. They have higher shelves and are screwed on with a large number of screws. They are made from metal 2 thick; 2.5 or 3 mm.

Designation	Size (length height width, metal thickness) in mm	Designation	Size (length height width, metal thickness) in mm
Reinforced corner	105 × 105 × 90 × 2	Reinforced corner KP5	140 × 140 × 65 × 2.5
Reinforced corner	130 × 130 × 100 × 2	Reinforced corner KP6	105 × 172 × 90 × 3.0
Reinforced corner	105 × 105 × 90 × 2	Reinforced corner KP7	145 × 145 × 90 × 2.5
Reinforced corner	50 × 50 × 35 × 2	Reinforced corner KP8	145 × 70 × 90 × 2.5
Reinforced corner	70 × 70 × 55 × 2	Reinforced corner KPL1	90 × 90 × 65 × 2
Reinforced corner	90 × 90 × 40 × 2	Reinforced corner KPL11	90 × 90 × 65 × 2
Reinforced corner KP1	90 × 90 × 65 × 2.5	Reinforced corner KPL2	105 × 105 × 90 × 2
Reinforced corner KP11	90 × 90 × 65 × 2.5	Reinforced corner KPL21	105 × 105 × 90 × 2
Reinforced corner KP2	105 × 105 × 90 × 2.5	Reinforced corner KPL3	90 × 50 × 55 × 2
Reinforced corner KP21	105 × 105 × 90 × 2.5	Reinforced corner KPL4	70 × 70 × 55 × 2
Reinforced corner KP3	90 × 50 × 55 × 2.5	Reinforced corner KPL5	50 × 50 × 35 × 2
Reinforced corner KP4	70 × 70 × 55 × 2.5	Reinforced corner KPL6	60 × 60 × 45 × 2

A few additional words need to be said about some of the corners shown in the table, since their description requires clarification:

— KR11 and KR21 are improved corners, often labeled as KR1 and KR2. These elements have an oval-shaped anchor hole, which reduces the risk of bolt breakage in the event of shrinkage of the structure.

— KR5 and KR6 are corners used for fastening elements that bear a large load-bearing load. Corner KR6 is also equipped with an oval hole, and it is recommended to use it when creating a rafter system on a new house, which will still shrink. These models are in demand when installing structures that have a lot of weight.

— The KM corner is made of perforated steel and is used for fastening rafters with a large cross-section. It is especially suitable for wooden buildings. This corner secures the structural elements very reliably, and when using it, there is no need to insert the rafters into the mauerlat - it is enough to cut out the correct angle first.

— The KMRP corner is used to fasten the parts of the rafter system at right angles, including the rafters with the Mauerlat. It also differs from conventional angles in its elongated hole, which allows displacement during shrinkage without damaging the mounting bolt. It can be used in structures where it is impossible to insert one element into another.

KMRP corners are produced from steel 2 mm thick. Three varieties are available:

Angle designation	Dimensions in mm
	a	b	c
KMRP1	60	60	60
KMRP2	80	80	80
KMRP3	100	100	100

Another option for securing the rafters to the mauerlat is to install them between two boards sawn under certain angle, and additionally in the lower part fixed with metal corners or LK fasteners.

This fastening of the rafters provides good rigidity and reliability. This method is well suited in cases where the rafter needs to be secured at the desired angle, lifting it above the horizontal plane of the Mauerlat, but securing it to the vertical outer side.

A method of attaching rafters to a mauerlat made from timber of not too large a cross-section. This is done by strengthening the beam with wooden pads of the required thickness.

Sections of boards are attached to the mauerlat using nails or self-tapping screws in the places where the rafter legs will be installed.

In this case, cuts of the required configuration and depth are made in the rafters. The rafter legs are securely fixed to the wall using steel wire, which is secured to a driven steel spike.

In addition to the above-described fastening methods, the rafters are nailed to the Mauerlat using brackets. It should be noted that this method is quite common and has been used for a very long time. If these elements are properly secured, the rafter system will last for many years.

The staples can be of different sizes and are driven in at different joints.

Another fastening element that is used as an auxiliary element is TM perforated tape. It is used to strengthen the fastening unit if additional fixation is necessary.

In some cases, this element may be irreplaceable, so it also cannot be excluded when installing rafter legs on the mauerlat.

Features of rafter systems

The rafter system is selected depending on the location of the load-bearing walls of the building. Each of the systems has its own additional supporting or tightening elements.

A system with layered rafters is distinguished by the fact that it has one or more support points, in addition to load-bearing walls. In this regard, a significant part of the load is removed from the side walls.

In the form of additional supporting elements, side posts and “headstocks” are used, supporting the ridge and secured to the floor beams. And the beams themselves, in turn, simultaneously serve as tension for the structure, and also lighten the load from the rafter system on the load-bearing walls.

Layered rafters are attached to the Mauerlat most often with sliding joints, which can move when the walls shrink or deform, leaving the roof structure intact. This is especially important to take into account in new buildings, since any newly built building necessarily shrinks under the influence of temperature fluctuations and ground movements.

Hanging rafters

The rafters are called hanging due to the fact that they have no other supports besides the two side load-bearing walls. It turns out that they seem to hang over the internal space of the building. In this case, the entire load from the roof frame structure falls on the Mauerlat.

To attach hanging rafters to the Mauerlat, rigid fastenings are used with no degree of freedom of movement, since the frame structure has only two points of support.

The hanging rafter system is braced and therefore puts a lot of pressure on the walls.

To remove part of the load from the walls of the building, additional elements are used, such as struts, headstocks and bolts, which pull the system to the ridge beam and evenly distribute the load on all walls. The crossbars are installed parallel to the floor beams and tighten the rafters together. Without these additional parts, the design may become unreliable.

Calculation of rafter installation

In order for the rafter system to be reliable and durable, in addition to the optimal connection method, you need to choose the correct spacing of the rafter legs. This parameter is selected depending on the size of the rafters (their cross-section and length between support points), as well as on the roof structure.

In this table you can obtain information about the necessary parameters for installing a reliable rafter system.

Installation pitch of rafter legs in mm	Length of rafter legs in mm
	3000	3500	4000	4500	5000	5500	6000
600	40×150	40×175	50×150	50×150	50×175	50×200	50×200
900	50×150	50×175	50×200	75×175	75×175	75×200	75×200
1100	75×125	75×150	75×175	75×175	75×200	75×200	100×200
1400	75×150	75×175	75×200	75×200	75×200	100×200	100×200
1750	100×150	75×200	75×200	100×200	100×200	100×250	100×250
2150	100×150	100×175	100×200	100×200	100×250	100×250	—

Several rules for attaching rafters to the Mauerlat

In order for the fastenings to be reliable, it is necessary to follow a number of rules that are provided for this process:

If metal connecting parts are used for fastening, then they must be fastened to the wooden connecting elements with maximum care - with high-quality self-tapping screws of the required length.
If the rafters are to be laid in grooves in the mauerlat, then the dimensions must be precisely adjusted. This will ensure a tight, reliable installation of the rafters into the prepared cut, which should have a depth of ⅓ of the Mauerlat. However, it should be remembered that such a rule will only be valid if the Mauerlat is made of a powerful block with a cross-sectional size of at least 150 × 150 mm.

In order not to weaken the Mauerlat, most often cuts are made in the rafter leg itself at the desired angle, and additionally the knot is then fixed with corners. In this case, the cut should not exceed ¼ of the thickness of the rafters. This fastening is rigid and can be used in a hanging rafter system.

When using bolts to fasten rafters with slopes, tie rods and other wooden elements, be sure to install a washer or metal plate, to avoid the nut from sinking into the wood and, accordingly, weakening the structure.
Fastening rafters to the mauerlat only with nails or self-tapping screws is considered unreliable, so it is necessary to use corners or other metal fasteners of various configurations.

When installing rafters on wooden walls, be it a hanging or layered system, it is recommended to fasten them to the Mauerlat using a sliding fastener, especially if roofing material has quite a lot of weight.

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The main components for connecting rafters to the Mauerlat

To begin with, it is worth highlighting the main mounting elements for installing the roofing system.

These include:

corners - used when necessary to firmly install the rafter legs on the mauerlat. Capable of making the fastening more durable. The advantage is that there is no need to make cuts in the wooden parts - the corners are secured with ruff nails or self-tapping screws;
brackets are made of galvanized steel. Installation is carried out without cutting down the wood; the brackets are secured with anchors, nails or screws;
perforated mounting tape - used for additional fixation of the connection unit, giving the roofing system tenacity. Installation requires screws or nails;
LK fasteners, “sleds” - used to protect the roof from deformation during soil subsidence and shrinkage of the building;
bolts with nuts, nails, wire ties, self-tapping screws, and some other elements.

All connecting parts must be of high quality and reliable - you should not skimp on this.

It is necessary to exclude the use of all kinds of gaskets, which over time can become deformed and fall out.

The rafter structure consists of a mauerlat, valleys, rafter legs, ridge partitions, purlins, and sheathing.

To understand how all the components are connected to each other, you need to determine what the coupling nodes of the Mauerlat and rafters are.

To begin with, the Mauerlat is attached to the axis of the wall. There are few fastening methods.

The first method is suitable for roof installation large area. To do this, an armored belt is poured around the entire perimeter of the wall, into which metal pins are immediately inserted.

In this case, the Mauerlat will be attached to the wall with studs that pass through the beam and are mounted.

When using the second method, the Mauerlat is attached to the wall using wire. To do this, you need to lay it between layers of bricks (3-4 rows before the end of the masonry).

In this case, you can fix the rafter with wire directly to the wall. However, this kind of connection can compromise the integrity of the wall.

If the knot is attached to a beam, then a “tooth with a tenon” is prepared in the rafters, and a stop for the tenon must be cut out in the beam with this socket.

The notch is made at a distance of 0.2 - 0.5 m, starting from the part of the beam that hangs down. A single “tooth” is made with a spike that will prevent it from moving to the sides.

In the case of a flat roof, if the degree of inclination is less than 30°, then the rafter legs are mounted with increased support on the beam.

There are three types of ridge connection: end-to-end, overlapping, and attached to a ridge beam.

In the first case, one part of the rafters must be cut at the same degree as the slope of the roof, and then it must be rested against the corresponding rafter on the reverse side (they must be cut equally).

It is advisable to cut corners using a stencil. For fixation, 2–4 nails are usually used. The joint is secured by placing a plate of wood or metal on it.

Installation on a ridge beam is similar to the previous mount. The difference is that a ridge beam is fixed between the rafters cut at an angle. This type of knot is complex, for this reason it is practically not used in construction.

Overlapping is the most popular way, although similar to the first one. The main difference is that the connection is made not end-to-end, but overlapping. The rafters are connected by side cuts. Attract them with nails, bolts or studs.

Schemes and methods of attaching rafters to the Mauerlat

Fastening the rafters is one of the most important moments in roof construction. The condition of the roof under different circumstances (snowfalls, showers, temperature fluctuations) will depend on the method of fastening the support beams.

Rigid fastening scheme

For single-pitched and gable roofs, a rigid installation scheme of the rafter system to the base is used.

The system of this fastening eliminates the possibility of affecting the connections of the nodes. During the operation of the roof, possible shifts and deformations of the roofing system are minimized.

High strength is based on the use of metal corners. Additionally, it is recommended to fix the beam to the base on both sides with special corners - this will help prevent lateral displacements.

The installation of the rafter system is carried out at the desired angle, and it is necessary to set a certain slope for the structure, fixing it with side nails. When using a rigid design, anchors and wire are often used.

Sliding mounting option

Everyone knows that wood expands when there is high humidity, and contracts during hot and dry weather.

For this reason, in the construction of wooden houses, not a rigid, but a sliding scheme is often used.

When using this fixation scheme, in certain cases, the nodes of the truss structure may move in the desired direction. The gable roof design is suitable for using this fastener.

There are several types of fastening for this scheme. So, you need to make a recess on the rafter leg, then fasten the Mauerlat and the beam, then secure everything with nails.

Moreover, this must be done in such a way that the nail passes right through the beam and sits firmly in the base.

Another type of fixation can be done using metal staples and special plates. An element called “sled” is very often used.

Despite the fact that the scheme is called sliding, all structural elements are securely fastened together, but if necessary, they are evenly shifted.

The use of this fastening scheme is due to the fact that over time the soil shifts and the foundation sags - this leads to damage to the roof frame.

The sliding scheme helps to avoid unnecessary changes and destruction of the roof structure.

How to attach rafters to the mauerlat? It depends on the location of the load-bearing walls. Methods of attaching rafters to the mauerlat are divided into layered and hanging. Layered, in turn, are divided into spacer and non-spacer.

Layered method of fastening rafters

The use of a non-thrust device for rafter legs makes the pressure on the load-bearing walls less. On a pre-fixed tightening there are vertical posts, which will be the support points. This method is suitable for single-pitch and gable roofs that have a main load-bearing wall.

The support unit of the rafters to the mauerlat is often made hinged (sliding). If you use movable hinges in the connections, the roof structure can be lowered by several centimeters.

This property is very useful in the first years after construction, since over time the new building settles.

If, together with the supporting walls, the roof does not change its position, then the walls of the building may be subject to deformation or destruction. This will not happen if the rafters are attached in a layered manner.

When using rafter fasteners of the spacer system, rigid fasteners must be used without the use of hinges.

In this design, all connections are made thanks to the support bar. It turns out that the top of the attached rafter rests on the top of the corresponding rafter on the other side.

How to properly fasten the rafters in this case? Fastening to the required Mauerlat must be carried out to the wall.

For this purpose, a rigid frame is suitable, fixed to the wall with anchors or brackets, in the corners of which special corners must be installed.

This design is suitable if you need to install a roof for small houses. For large buildings, the Mauerlats are installed in special concrete gutters and fastened with anchors. The main load in such a system falls on the gutter and is used in the construction of cinder block buildings.

Hanging mounting scheme

Hanging rafters are intended for use in the construction of buildings without load-bearing walls inside. The support points in this case are only the external load-bearing walls.

The fastening of this design is carried out using a rigid type unit. Other options are not suitable, since the connection of rafters with a mauerlat on the walls is the only support for the entire pitched or gable roof.

Rafters installed in a hanging manner place a strong horizontal load on the walls.

To reduce pressure, puffs (crossbars) are used. They are installed at the base of the structure perpendicular to the rafters. Attached to all the beams, the crossbars hold the rafters together.

You cannot build a roof with hanging rafters without using tie-downs.

A few important nuances

you need to use only high-quality materials. There is no point in saving on this, since the durability of the roof and the safety of the residents of the house directly depend on the reliability of the structure. Negligence during roof installation is fraught with all sorts of displacements or, even worse, collapse of the entire structure;
all work should be carried out extremely carefully; the use of different gaskets is unacceptable;
It is not recommended to use the installation of rafters without a Mauerlat, as there may be a risk of distortion and damage to the integrity of the walls of the house;
the most suitable method is the sliding fixation method, which will avoid deformation of the rafter system in the event of soil subsidence.

The arrangement of the roof of the house should be approached very seriously - you should not rush when attaching the rafters to the mauerlat.

Before starting construction work, the truss structure must have a clear design; all places of connecting nodes must be immediately identified.

A sufficient supply of all mounting elements of proper quality is required. With this approach, you can be confident in the reliability and durability of the roof.

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Main elements of the rafter frame

The rafter frame of the roof of a house is a system of interconnected supporting elements made of wood or metal that give the structure its shape, slope, and also evenly distribute its weight between the load-bearing walls. Its main component is the rafter legs, which are beams installed at an angle, which are connected in pairs along the slope, forming a ridge at the top point of their connection. There are two main types of rafters:

Layered. Layered rafters are called supporting elements that have two points of support in the roof structure - on the ridge girder and the mauerlat. A rafter system of this type is used in structures that have one or more load-bearing walls inside on which rafters can be “leaned.” This fastening of the rafters allows you to relieve them through the use of additional vertical supports.
Hanging. Hanging elements are those that have only one support point, located where the rafters are attached to the wall or mauerlat. A hanging type rafter system experiences load not only in bending, but also in expansion, so it is reinforced by horizontal compensating elements (crossbars, tie rods, tie rods).

Note! In most of the most popular rafter systems, the rafters are attached to the Mauerlat. Mauerlat is a massive beam or beam with a cross-section of 150x150 mm or 200x200 mm, laid along the load-bearing walls of the structure, on which the rafter legs will subsequently rest. It softens the pressure on the walls of the house and also distributes the weight evenly roofing pie. You can attach the Mauerlat to the upper chord of the walls using anchor bolts or embedded metal studs.

Main connecting nodes

The rafter frame is called a system because all its elements are closely interconnected and fixed, as a result of which the roof structure acquires a stable shape, rigidity and high load-bearing capacity. Each connecting node between its parts is a vulnerable point that can easily deform under load, so all fastenings must be carried out strictly according to technology. Experienced craftsmen identify the types of connections in the roof structure:

Attaching the rafters to the ridge beam. This connecting unit is typical only for layered rafter systems, in which the upper part of the rafter leg rests on a ridge girder mounted on vertical posts. The rafters can be attached to it using metal plates, nails or sliding slide fasteners.
Fastening the rafters to the mauerlat. The most important fastening point of the rafter frame is considered to be the junction of the mauerlat beam with the rafter legs. You can fix the rafters on it using nails, metal corners or wooden blocks.
Connecting the rafters to each other. To lengthen the rafter legs, if the length of the slope exceeds the standard length of lumber, they are assembled from several elements connected to each other using nails, glue or metal plates.
Connection of rafter legs with auxiliary supporting elements. In truss frame construction, rafters can be connected to tie rods, transoms, or struts to increase rigidity, strength, and load-bearing capacity.

Please note that any cuts made to attach the rafters to the beams, mauerlat or other structural elements of the frame lead to a decrease in their strength, so experienced craftsmen recommend connecting them together using corners and overlays.

Fixation methods

When deciding how to attach rafters to a mauerlat or ridge girder, you need to choose the right fastening hardware. The modern construction market has a huge range of fasteners of various designs and sizes. The main criteria for choosing fasteners are the material used to make the rafters, their cross-section, as well as the type of load to which they are subjected. There are the following methods of fastening rafters:

Using metal corners. Metal corners with holes for screws or nails are the most reliable and durable option for rigidly attaching rafters to the mauerlat, walls or ridge girder. They allow you to increase the rigidity and load-bearing capacity of the rafter frame structure many times over.
Using metal plates. To connect the elements of the rafter frame, perforated steel plates are also used, which make it possible to fix them without making a gash in the mauerlat or rafters, thereby maintaining their high strength qualities.
With the help of "chocks". Chocks are small blocks of square cross-section that are installed between the rafters and the ridge girder or mauerlat as spacers that increase the rigidity of the structure.
Using sliding fasteners. Another option for fixing rafters with a ridge purlin or mauerlat is the use of movable fasteners, which in everyday life are called sleds or sliders. Due to their mobility, it is possible to compensate for the change in the dimensions of the elements that occurs during the shrinkage process.

Experienced craftsmen believe that the most reliable way to fix rafters is to use metal corners that firmly connect the wooden elements to each other, rigidly fixing the angle between them. The corner that covers the joint between the rafter leg and the ridge beam or mauerlat serves as a kind of spacer between them.

Types of fastenings

Tree - natural material, which in the process of equalizing humidity and drying gives significant shrinkage, due to which the linear dimensions of the structure change. That is why experienced craftsmen recommend erecting a roof for timber and log houses a year after construction, when the shrinkage process passes from the active to the passive phase. If you fix the wooden frame elements rigidly, then after drying the roof of the house may become deformed. Therefore, the following types of fastenings are used to connect rafters:

Tough. Rigid fastenings are those types of fastening fittings that are not able to compensate for changes in the size of wood during the drying process. They provide a strong, reliable fixation, however, they can cause deformation of the frame, leading to changes in the geometry of the roof, leaks, or even collapse of the structure. This type of fastener includes metal corners, metal plates and wooden “chocks”.
Mobile. Movable fastenings are methods of fixation that, due to parts sliding along their axis, can compensate for changes in the dimensions of the rafter frame during the process of shrinkage of the structure. The frame, secured with sliders or slides, “breathes” along with the house, adapting to its dimensions without causing deformation. With the help of such fastenings it is possible to erect roofs for wooden houses that have not undergone the shrinkage process.

Interestingly, there are several options for combinations of movable and fixed connecting nodes. The most common are rafter systems with one rigid and two sliding fasteners, which provide sufficient mobility with high strength and rigidity of the structure.

Types of fasteners

There is ongoing debate among experienced roofers as to what is the most effective way to attach rafters to floor beams and mauerlat. However, in most cases the problem is that in these conditions it is more practical to use nails or self-tapping screws. Both of these fasteners have their own advantages and disadvantages:

Nails are good because all you need to hammer them in is a hammer, which is available in every household. However, some craftsmen complain that hammering them in by hand takes too long. It is worth recalling that special jagged nails are used to fix the rafters, which securely adhere to the wood.
To assemble the rafter frame, galvanized self-tapping screws are used, which are not afraid of corrosion. Due to the thread, they are firmly screwed into the thickness of the wood, securely fixing the elements together. Screwing them in quickly and conveniently with a portable screwdriver. The disadvantage of this type of fastener is that during dismantling, removing screws from wood is long and tedious.

Most experienced roofers agree that to fix rafter legs it is better to use galvanized rough nails, the length of which is 5-3 mm greater than the thickness of the lumber. Properly selected fasteners are the key to high-quality and long-term fixation of the roof frame, which will not be afraid of either mechanical stress or wind load.

The layered rafter system can be a spacer or non-spacer structure. Whether the rafters will push the walls or not will depend on the correct choice of support nodes and articulation of the rafter legs; it is necessary to provide various measures for them to intercept the thrust or not.

On the design diagrams, circles are drawn at the structural nodes, indicating a hinged connection. The hinges are connected with claws to conditional supports, along which the degree of freedom of the assembly can be visually represented. A hinge with two legs embedded in the support assumes that the node is motionless, but the beam can rotate in the hinge, that is, the node has one degree of freedom - rotation. A hinge with legs standing on a sliding support or slider shows that the assembly has two degrees of freedom - the ability to rotate the beam and horizontal displacement. Three degrees of freedom of the node allow horizontal, vertical displacement and rotation; such a node is simply drawn as a circle and can be cut into a rod representing a beam. If the node is embedded in a beam, then it is called a split beam, that is, the beams located to the left and right of the hinge can, with some assumptions, be considered as separate elements. If a circle (hinge) is drawn under a beam, then the beam lying on it is called continuous. The three-degree-of-freedom hinge embedded in the beam, in many cases, makes it an instantly variable system, that is, a rather unstable structure. A node with a zero degree of freedom means rigid pinching of the end of the beam and prohibits it from any displacement: horizontal, vertical and rotation (Fig. 19).

Rice. 19. Examples of schematic representation of nodes

In the calculation diagrams, other schematic representations of nodes may be used, but they are all generally understandable, and if ambiguities suddenly arise, you just need to mentally imagine in which direction the node can “go” when a load is applied to it. The transverse dimensions of the beams relative to their length are small, so the beams (rafters, etc.) are drawn as rods, and the load in them is distributed as if only along the longitudinal axis of the element, and the calculation of the entire structure is carried out for the rod diagram.

It should be noted that the words: horizontal displacement and rotation do not mean at all that, for example, a slider - a unit with two degrees of freedom - moves arbitrarily in the horizontal direction. In fact, this node is quite well fixed, but allows the end of the beam to move due to load, temperature and humidity changes without excessive development of internal stresses in it. This unit simply does not transmit thrust, and rotation when bending the beam is possible only within standard limits. The slider will truly crawl (forgive the tautology) only under loads exceeding the maximum permissible. The word “hinge” also does not need to be taken literally. Yes, the ends of the beams can be connected with a bolt or an actual specially designed hinge, but most often it is a regular nail connection. For example, you can take a board and nail it at one end with 3-4 nails, say, to a wooden wall. Nothing prevents us from taking it by the other end and calmly turning it to a certain angle. In this case, the nail fastening acts as a hinge. However, if the number of nails is increased and they are designed for a load that does not allow shearing (bending), then rotation becomes impossible; here we get a beam with a pinched end, but when the load exceeds the calculated one, the node again becomes a hinge. Therefore, it is very important to initially determine the load under which the system will operate. Since the excess of the actual load over the calculated one leads to a change in the operation pattern of the units and destruction of the entire structure.

The connections of layered rafters related to various schematic representations of nodes are presented in Figure 20.

rice. 20.1. Knots for supporting rafters on purlins and mauerlat. Hinge with one degree of freedom (pivot only)

rice. 20.2. Knots for supporting rafters on purlins and mauerlat. Slider - hinge with two degrees of freedom (rotation and shift)

rice. 20.3. Supporting unit for rafters on the purlin. Hard pinching

Depending on the problem being solved when designing a roof, the nodal joints of the rafters may differ from those presented in Figure 20. The main thing is to design in nodes with two degrees of freedom: rotation arising from the bending of the rafters and shift in the horizontal direction. And in nodes with one degree of freedom - rotation of the rafters. As a rule, the shift of the top or bottom of the rafters is ensured by horizontal notches, and the shift is limited by the rafters resting on each other and/or on the joining element: the mauerlat or purlin.

Let's try to explain the principle of fastening the rafters using an example. We can all easily imagine an ordinary ladder. The staircase is just like a staircase, nothing special: two poles (strings) and transverse sticks-steps. Let’s mentally put such a ladder against the wall, and for the purity of the experiment, we’ll minimize the friction forces by pouring oil on the floor and wall. What happens if you load a ladder and climb on it? The stairs will collapse. It has two degrees of freedom in the lower and upper supports. In the lower one, it has rotation and horizontal displacement, in the upper one it has rotation and vertical displacement. What needs to be done to make the ladder stable and support the load (person’s weight)? All you need to do is deprive it of one (out of four) degrees of freedom: horizontal in the lower or vertical in the upper support. In other words, you need to secure the bottom or top of the stairs. We get a stable and stable system. You can come up with a thought experiment with a ladder yourself, placing it in various situations, for example, if the ladder is long and rests on the wall from above, with strings with horizontal cuts or without cuts. How will she behave? Such brainstorm, helps in understanding the operation of layered rafters with various methods of support, in which it is not at all necessary to imagine the vectors of forces and degrees of freedom of the nodes, but you just need to predict whether the staircase will roll under load or remain motionless.

The importance of correct fastening of the rafters to the mauerlat cannot be overestimated. The rafter leg, resting on the Mauerlat, transfers the entire load from the roof directly to the structure of the outer wall of the building. In addition, this connection should prevent possible roof failure from strong wind loads.

Fasteners

To fasten wooden structures, fasteners are used that are made of sheet or profile steel, metric fasteners, nails, and staples.

For dowel connections, the following are used: bolts, nails, rods, claw washers.

If the diameter of the nail is less than 6 mm, then for soft wood they are driven in without first drilling the socket. For diameters greater than 6 mm, to avoid the formation of cracks in the wood, a socket measuring 0.9 times the diameter of the nail is drilled under the nail.

Staples are used only for connecting log or timber elements in the absence of the possibility of splitting the wood. It is advisable to place them in pre-drilled holes of a smaller diameter.

Types of rafter structure supports on the Mauerlat

Rafters can be of two types: hanging and layered. This depends on the possibility of them being supported on the walls. Hanging rafters have one support point on the mauerlat; the other end creates a ridge unit with a frontal support for two rafters. Layered rafters rest on the outer wall on one side and on the inner wall of the building on the other. Hanging ones, not having a second point of support, create a thrust from the deflection of the rafter structure. That is why they have a tightening at the bottom, which takes on the pushing forces.

Layered rafters

The layered rafters are fastened directly to the Mauerlat. Most often, for this purpose, an insert is made in the rafter legs. Its depth is provided for less than 1/4 of the height of the rafters. They are fixed on both sides using corners.

Layered rafter system: 1 - Mauerlat; 2 - perforated corner; 3 - lying down; 4 - rafter leg; 5 - stand; 6 - ridge run; 7 - transverse strut; 8 - waterproofing; 9 - longitudinal strut

Sometimes such fixation is carried out using staples. The staples are driven into both the rafters and the mauerlat.

This method of fastening the rafters and the Mauerlat is carried out using beam holders attached on both sides:

Often, to increase the rigidity of the connection, three nails are driven into the rafters. One vertically and two crosswise. Moreover, the length of the driven part of the nail must exceed 10 diameters of the nail and 2 thicknesses of the element that the nail pierces.

Important! Due to the fact that larch easily splits, connections with nails and staples cannot be used for it.

Hanging rafters

The hanging type of rafters is used for buildings with a width of 6 to 12 meters. With the hanging rafter leg option, the load from the rafters is transferred to the Mauerlat through a tightening. Here the strength of the rafters is not weakened by the tie-in device.

Hanging rafter system: 1 - Mauerlat; 2 - tightening; 3 - perforated corner; 4 - crossbar; 5 - ridge run; 6 - rafters; 7 - mounting bolts

When the length of the rafter leg is not enough to create the required roof overhang, it is cut off at the level of the mauerlat. The overhang is made using small wooden blocks (fillies).

Connection of rafters with Mauerlat depending on the material and design of the wall

The design of the walls, as well as the material from which they are made, directly influence the method of fastening the rafters to the Mauerlat.

Brick walls

In brick walls, the rafter legs are attached to the mauerlat using corners, staples, nails, etc.

To protect against the roof falling off in windy weather, the rafter legs are secured one after another in the wall using a twist (Ø 2-3 mm) of 2-3 wires to a crutch. The metal crutch is embedded in advance into the masonry 200-300 mm below the mauerlat. All wooden roof parts touching the brickwork should be protected from moisture with waterproofing pads in 2 layers (roofing felt, waterproofing, etc.).

Important! You cannot completely fill with bricks or fill with mortar the gaps between the wooden elements of the rafter supports and the brick walls. They should be open, but protected from moisture.

Wooden walls

A significant difference between the pairing of rafters and the Mauerlat for wooden walls is the need for a certain mobility of the rafters relative to the Mauerlat. A wooden house shrinks immediately after construction, which can damage the roof structure if the wooden elements are rigidly fastened.

A movable type of fastening is used here. It allows the rafter leg to have some freedom in two directions. For such connections, factory-made fasteners are used.

The mauerlat is protected from wind loads by connecting it to the penultimate crown of a log wall or wall made of timber. To do this, staples are driven into the Mauerlat and the wall. In houses made of timber or logs, the last crown of the wall often serves as the mauerlat.

Walls made of aerated concrete blocks

Aerated concrete blocks do not have sufficient strength to attach the roof to the walls. Therefore, a monolithic reinforced belt is made in them, in which metal pins are placed.

The Mauerlat is mounted on them through a pre-drilled hole and bolted to the belt. Here we must not forget about waterproofing between wood and concrete. Otherwise, the principle of fastening the mauerlat and rafters remains the same.

Connection of rafters to the Mauerlat depending on the rafter structure

The rafter system for constructing the roof of a building can have a huge variety of options. This is ensured by the fairly easy processing of wood as a building material. In general, several types of such systems can be distinguished: beams, arches, trusses and even frames.

In any particular case rafter roof There are some differences in the way the rafters are connected to the Mauerlat. For small buildings (barn, garage, small country house, etc.), you can make this connection yourself, guided by the fastening methods listed above.

For more critical buildings and structures, all interface elements are calculated, including metal fasteners. Based on the calculations made, the material, size and number of required structural parts are selected. That is why in such cases it is better to entrust the design calculations to specialists.

Several rules for choosing the method of connecting rafters to the Mauerlat

1. Standard wood moisture content is 12%. A freshly cut tree can have a moisture content of up to 100%. When wood dries, it deforms. If you use products for rafters that have not reached the standard moisture content, the integrity of the wood may be destroyed in the rigid connection of the mauerlat and rafters. It is advisable to use products of standard humidity, and also to exclude the possibility of moistening wooden parts by treating them with moisture-proof coatings.

2. If part of the rafter leg is in a warm room, and part in a cold room, different temperature and humidity operating conditions also affect the operation of the entire roof structure. In this case, it is necessary to provide additional protection in places where there are walls or ceilings from biological damage to the wood and exposure to moisture (treatment with special substances). Under such operating conditions, only rafters of rectangular cross-section are used.

3. When trimming the rafter leg, it should be taken into account that the length of the part that rests on the mauerlat should be less than the height of the rafters.

4. The junction of the rafters and the mauerlat in stone external walls should be insulated, protecting against freezing.

5. It is important that the possibility of condensation on the metal parts of the connections is excluded. If this does happen, then the wooden part in contact with the metal must be protected from moisture (elastic gaskets, mastics, sealing tapes, roofing felt, waterproofing, etc.).

Rafters are the load-bearing elements of the roof. Mauerlat, the basis of the rafter system, a kind of foundation for the roof structure. Proper fastening of the rafters to the mauerlat ensures the reliability of the entire structure, eliminates deformation of the rafter system, and prevents the roof from collapsing under the weight of an external load.

Mauerlat - correct installation

The Mauerlat, which is essentially the foundation of the roof, is made of logs or timber, laid along the perimeter, and is intended to ensure uniform transfer of the load of the roof structure to the walls and foundation of the building. In order for the roof to stand firmly, the rafters must be properly fastened to the mauerlat.

Important! IN wooden house made of timber or logs, the upper frame of the walls, the upper crown, serves as the mauerlat; no additions to it are required. In a house made of brick, foam or aerated concrete blocks, or building stone, a mauerlat must be installed.

Brick or block walls do not react well to undistributed loads; the blocks or bricks themselves are a poor material for fixing rafter legs. Even the most reliable fasteners are not firmly fixed in such walls; under load they can be torn out, resulting in deformation of the rafter leg and the entire roof.

The Mauerlat should be firmly attached at the upper ends of the walls along the entire perimeter to an equipped reinforced concrete belt. Attaching timber to concrete can be very reliable if the correct fasteners are used. Installation is in progress. It consists of pins, studs, anchors, embedded in concrete on which they are then made.

Important! The ends of the fastening pins should be bent from below, the distance between them is 1-1.5 m, the diameter of the fastener should be at least 15 mm. In the timber that will be used as a mauerlat, make technological holes for fasteners and secure the top of the fastening with bolts. Before installing the Mauerlat, lay a layer of waterproofing material.

After the base is installed, you can begin to work with the rafters.

Overview of fastener types

Fastening for any work related to roof construction is very important point. To attach strong and reliable rafters to the mauerlat, various metal fasteners are used, and also different geometries of inserts and cuts are used. For rafter fastening the following are used:

wire;
corner;
plates;
brackets;
LK elements;
nails;
self-tapping screws

And much more from perforated tape to studs. The use of one or another type of fastening requires different installation techniques.

If the rafters are fastened to the mauerlat using brackets, no cuts are required; if the LK fastening is used, anchors are not needed. The use of perforated tape makes the connection unit super-strong. Fastening with an angle is the most popular and in demand, since it does not need to be cut into the wood of the rafter leg; the angle is easily mounted with self-tapping screws.

Important! You can't skimp on fasteners. It must be of high quality with an anti-corrosion top layer, galvanized. Fasteners that rust in a beam destroy it.

Principles of connecting rafter legs to the Mauerlat

The design features of the roof determine how the rafters are attached to the mauerlat. Spacer rafter structures, as well as those in which spacers are not used, rest on the Mauerlat. Slab and hanging rafters can rest on it; the connection can be rigid and sliding.

A rigid connection is such a connection between the rafter legs and the Mauerlat, in which shifts, displacements, and bends of the elements are impossible. The immobility of the connection is achieved by fastening using a corner. A saddle is cut out in the rafter leg, this reduces the strength, so it is additionally reinforced with brackets, tightened with bolts, and also the rafter attachment point is connected to the Mauerlat by twisting wire at the locations of the anchors embedded in the reinforced concrete support.

A sliding fastening, a slide for rafters to the mauerlat, differs from a rigid fastening in that it allows some displacement of the rafter leg relative to the base, this avoids deformation and failure of the roof during shrinkage, snow and wind loads.

Important! If during the installation process of attaching a rigid type of rafter leg to the mauerlat it is necessary to make a nest or notch, such elements should be made on the rafter, and not on the mauerlat. The foundation cannot be weakened.

Proper support of the rafter leg with the Mauerlat ensures the reliability of the roof and its durability. With any method of support, in order to fix the rafters on the mauerlat, it is important to observe three fundamental points:

correct and precise making of cuts, cuts, etc., for a perfect fit of the elements;
the use of washers, nuts, and groovers to prevent the fastener from sinking into the wood;
It is unacceptable to use pads that can change shape over time, which will lead to load redistribution and destruction.

Correct installation of the roof support system guarantees its longevity.

Types of connection of rafters with Mauerlat

The rafter system consists of many elements, but the main ones are the rafters.

Important! How to attach the rafters to the mauerlat depends on what kind of rafters are used (sloping, hanging), on the loads and how massive the roof is.

The fastening can be sliding and rigid, closed and removable.

The most used connection of rafters with Mauerlat:

Installation of rafters on the Mauerlat is carried out using improved corners KR1, KR2. Their design provides technological holes for anchoring. The oval shape of the holes reduces the risk of the anchor bolt being pulled out when the wood base of the structure dries out. Also reliable are the corners KR5, KR6, which are needed to attach the rafters to the Mauerlat under heavy loads of a massive roof. It is better to securely fasten the rafters to the mauerlat, if they have a large cross-section, with perforated corners of the KM. This fastening is very reliable, no insertion is required, but an exact angle is required.

Important! For fastening at right angles, a reinforced KMRP corner is used; it differs from conventional corners by an elongated hole, it is used to compensate for roof displacement, it is made in such a way that during such processes no damage to the fastening elements occurs, it is especially suitable where it is impossible to insert one part into another. The corner is made of durable steel 2mm thick.

Another type of connection is installation between boards. The boards are fastenings; they are cut at the desired angle and fixed at the bottom with corners.

Methods of fastening rafters using board linings, twisted wire, staples, to the Mauerlat are also used. These types of fastenings have been known for a long time, are popular and economical.

Types of rafter supports on the Mauerlat

Mostly gable roofs are erected for residential buildings. With a gable structure, special attention is required to the support of the rafters on the mauerlat. It is clear that a wooden base requires wooden beams.

Important! Rafters required correct form, without knots, calibrated and milled on all sides. The cross-section of the gable roof rafters is 40x150mm, the Mauerlat is 100x100mm.

The choice of fastening type depends on the geometry of the gable roof. You can fasten the rafters using all the methods listed above. It is also worth considering the hinged attachment points of the rafters to the Mauerlat.

A hinge joint is a type of connection that allows a beam to move in a circle. This happens with the help of one nail or self-tapping screw screwed into the Mauerlat. There is a node with one, two and three degrees of freedom. A unit with two degrees of freedom allows the beam to move horizontally; the rafters are secured with slides. With three degrees of mobility, the unit is installed using a slider, a special support for sliding the rafters in a vertical, horizontal position, in addition, the rafter can rotate in a circle. For this purpose, a special hinge is made, which is attached to the base.

Important! The most typical method for a gable roof is to use a zero-freedom assembly. The rafter is fastened with corners on both sides, remaining motionless.

The complex geometry of a gable roof requires the use of layered and hanging rafters. Beams supported on a base are effectively secured using perforated tape.

Layered rafters rest on the base and other support points, thereby relieving part of the load. Side posts can be adjacent to them, ridge headstocks, rafters tighten the structure, strengthening it. Layered structures do not rest on the base, but slide along it. Hanging rafters do not rest on the base; hanging over the interior of the roof, they are supported by the side load-bearing walls.

Basic rules for pairing rafters with the Mauerlat

For a reliable connection, you need to carefully fasten the connecting elements and select them of the required sizes. It is necessary to accurately check the cuts, making them no more than a third of the size of the base. Use high-quality timber for the base of the correct section.

Important! You cannot use only nails and self-tapping screws for fastening; such fixation cannot be considered reliable; metal fasteners of various types should be used.

The roof will be strong and durable if the calculations are carried out correctly, the material is selected correctly and the joints are installed correctly.

Attaching the rafters to the mauerlat is a significant step in the construction of the roof. The strength and safety of the roof depends largely on the quality of installation of the rafter system, in particular, on the correct choice of fastening elements and proper connection of the supporting structure units.

Attachment points for rafters to the Mauerlat

There are two ways to attach rafters to the Mauerlat:

hard and
sliding.

The following support units are distinguished:

articulated

one degree of freedom. Allows a beam made of wood or metal to rotate in a circle. This state can be achieved by using one screwed-in nail or self-tapping screw for fixation;
two degrees of freedom. Rotation of the beams in a circle or slight movement in the horizontal plane is allowed. It is achieved by fastening the rafters either using a slide or using a sliding support - a slider made from mounting angles;
three degrees of freedom. The rafters can be moved in a circle, as well as in vertical and horizontal planes. A similar effect is obtained due to a specially made hinge, which is screwed into the murlat;

zero degree of freedom. The ends of the beam are rigidly fixed at both ends, which prevents it from moving. This option is mainly used in brick buildings.

Rafter leg mounting options

To perform the lower assembly of supporting the rafter leg on the support beam, one of the following methods is generally chosen:

sliding, which is a movable connection: the lower end of the beam is held on the mauerlat only with the help of fasteners that do not prevent it from sliding along the beam;
spacer is a fixed coupling unit with a rigid support of the rafters in the timber.

Both of these options have the same right to life and are used taking into account the shape of the roof and the features of the rafter system.

Fastening methods with and without sawing

rigid fixation, which works on compression formed by the emphasis aimed at inner side support beam;
movable fixation formed by the tooth on the outside. To prevent the rafter legs from slipping off the murlat, they are fixed with fasteners that work in tension, for example, staples or corners.
The cut in the rafter beam is sometimes replaced by a board that is nailed to the rafter leg.

Fasteners for rafters and rules for working with them

Attention!

In the process of connecting wooden parts with screws (bolts), metal washers must be used underneath them. This simple technique will help avoid fasteners from sinking into the wood.

Fastening work is carried out in a certain order. We bring to your attention several of the simplest methods for sawing and subsequent adjustment of rafters.