The design of the gable roof truss system. Types of gable roof truss system: for small and large houses

At the heart of every roof is a large number of beams, rafters, posts and purlins, which are collectively called the rafter system. Behind centuries-old history Many types and methods of its organization have accumulated, and each has its own characteristics in the construction of nodes and cuts. Let's talk in more detail about what the rafter system of a gable roof can be and how the rafters and other elements of the system should be attached.

Design of a gable roof truss system

In the context gable roof is a triangle. It consists of two rectangular inclined planes. These two planes are connected at the highest point into a single system by a ridge beam (purlin).

Now about the components of the system and their purpose:

Mauerlat is a beam that connects the roof and walls of a building, serves as a support for rafter legs and other elements of the system.
Rafter legs - they form inclined planes roofs and are a support for the sheathing under roofing material.
Ridge purlin (bead or ridge) - combines two roof planes.
A tie is a transverse part that connects opposite rafter legs. Serves to increase structural rigidity and compensate for thrust loads.
Lezhny - bars located along the mauerlat. Redistribute the load from the roof.
Side purlins - support the rafter legs.
Racks - transfer the load from the purlins to the beams.

There may still be fillies in the system. These are boards that extend the rafter legs to form an overhang. The fact is that to protect the walls and foundation of the house from precipitation, it is desirable that the roof ends as far from the walls as possible. To do this, you can take long rafter legs. But the standard length of lumber of 6 meters is often not enough for this. Ordering non-standard is very expensive. Therefore, the rafters are simply extended, and the boards with which this is done are called “fillies”.

There are quite a few designs of rafter systems. First of all, they are divided into two groups - with layered and hanging rafters.

With hanging rafters

These are systems in which the rafter legs rest only on the external walls without intermediate supports (load-bearing walls). For gable roofs, the maximum span is 9 meters. When installing a vertical support and a strut system, it can be increased to 14 meters.

Hanging type rafter system The good thing about a gable roof is that in most cases there is no need to install a mauerlat, and this makes the installation of rafter legs easier: there is no need to make cuts, just bevel the boards. A lining is used to connect the walls and rafters - wide board, which is attached to studs, nails, bolts, crossbars. With this structure, most of the thrust loads are compensated, the impact on the walls is directed vertically downwards.

Types of rafter systems with hanging rafters for different spans between load-bearing walls

Gable roof rafter system for small houses

Exists cheap option rafter system when it is a triangle (photo below). Such a structure is possible if the distance between the external walls is no more than 6 meters. For such a rafter system, you can not calculate the angle of inclination: the ridge must be raised above the tie to a height of at least 1/6 of the span length.

But with this construction, the rafters experience significant bending loads. To compensate for them, either rafters of a larger cross-section are taken or the ridge part is cut in such a way as to partially neutralize them. To give greater rigidity, wooden or metal plates are nailed on both sides at the top, which securely fasten the top of the triangle (also see the picture).

The photo also shows how to extend rafter legs to create a roof overhang. A notch is made, which should extend beyond the line drawn from interior wall up. This is necessary to shift the location of the cut and reduce the likelihood of the rafter breaking.

Ridge knot and fastening of rafter legs to the backing board when simple version systems

For mansard roofs

Option with installing a crossbar - used when. In this case, it serves as the basis for lining the ceiling of the room below. For reliable operation systems of this type, the crossbar cut must be hingeless (rigid). The best option- half frying pan (see picture below). Otherwise, the roof will become unstable to loads.

Please note that in this scheme there is a Mauerlat, and the rafter legs must extend beyond the walls to increase the stability of the structure. To secure them and dock them with the Mauerlat, a notch is made in the form of a triangle. In this case, with an uneven load on the slopes, the roof will be more stable.

With this scheme, almost the entire load falls on the rafters, so they need to be taken with a larger cross-section. Sometimes the raised puff is reinforced with a pendant. This is necessary to prevent it from sagging if it serves as a support for ceiling cladding materials. If the tie is short, it can be secured in the center on both sides with boards nailed to the nails. With a significant load and length, there may be several such belays. In this case, too, boards and nails are enough.

For large houses

If there is a significant distance between the two outer walls, a headstock and struts are installed. This design has high rigidity, since the loads are compensated.

With such a long span (up to 14 meters), it is difficult and expensive to make the tie in one piece, so it is made from two beams. It is connected by a straight or oblique cut (picture below).

For reliable joining, the connection point is reinforced with a steel plate mounted on bolts. Its dimensions must be larger than the dimensions of the notch - the outer bolts are screwed into solid wood at a distance of at least 5 cm from the edge of the notch.

In order for the circuit to work properly, it is necessary to make the struts correctly. They transfer and distribute part of the load from the rafter legs to the tie and provide structural rigidity. Metal pads are used to strengthen connections

When assembling a gable roof with hanging rafters, the cross-section of lumber is always larger than in systems with layered rafters: there are fewer load transfer points, therefore each element bears a greater load.

With layered rafters

In gable roofs with layered rafters, their ends rest on the walls, and the middle part rests on load-bearing walls or columns. Some schemes push through the walls, some don't. In any case, the presence of a Mauerlat is mandatory.

Non-thrust schemes and notch units

Houses made of logs or timber do not respond well to thrust loads. For them they are critical: the wall may fall apart. For wooden houses The rafter system of a gable roof must be non-thrust. Let's talk about the types of such systems in more detail.

The simplest non-thrust rafter system diagram is shown in the photo below. In it, the rafter leg rests on the mauerlat. In this version, it bends without pushing the wall.

Pay attention to the options for attaching the rafter legs to the Mauerlat. In the first, the support area is usually beveled, its length being no more than the section of the beam. The depth of the cut is no more than 0.25 of its height.

The top of the rafter legs is laid on the ridge beam, without fastening it to the opposite rafter. The structure turns out to be two pitched roofs, which in the upper part are adjacent (but not connected) to one another.

The option with rafter legs fastened at the ridge part is much easier to assemble. They almost never push against the walls.

To operate this scheme, the rafter legs at the bottom are attached using a movable connection. To secure the rafter leg to the mauerlat, one nail is driven from above or a flexible steel plate is placed from below. See the photo for options for attaching rafter legs to the ridge girder.

If you plan to use heavy roofing material, you need to increase bearing capacity. This is achieved by increasing the cross-section of the rafter system elements and strengthening the ridge assembly. It is shown in the photo below.

Reinforcing the ridge assembly for heavy roofing material or for significant snow loads

All of the above gable roof schemes are stable in the presence of uniform loads. But in practice this practically never happens. There are two ways to prevent the roof from sliding towards a higher load: by installing a screed at a height of about 2 meters or by struts.

Options for rafter systems with contractions

Installing contractions increases the reliability of the structure. In order for it to work properly, it needs to be secured to them with nails at the places where it intersects with the drains. The cross-section of the timber for the scrum is the same as for the rafters.

They are attached to the rafter legs with bots or nails. Can be installed on one or both sides. See the figure below for attaching the screed to the rafters and ridge girder.

In order for the system to be rigid and not “crawl” even under emergency loads, it is enough to provide a rigid fastening in this option ridge beam. In the absence of the possibility of its horizontal displacement, the roof will withstand even significant loads.

Layered rafter systems with struts

In these options, for greater rigidity, rafter legs, also called struts, are added. They are installed at an angle of 45° relative to the horizon. Their installation allows you to increase the span length (up to 14 meters) or reduce the cross-section of beams (rafters).

The brace is simply placed at the required angle to the beams and nailed on the sides and bottom. Important Requirement: the strut must be cut accurately and fit tightly to the posts and rafter leg, excluding the possibility of its deflection.

Systems with rafter legs. The top is a spacer system, the bottom is a non-spacer system. The correct cutting nodes for each are located nearby. Below are possible strut mounting schemes

But not in all houses the average load-bearing wall is located in the middle. In this case, it is possible to install struts with an angle of inclination relative to the horizon of 45-53°.

Systems with struts are necessary if significant uneven shrinkage of the foundation or walls is possible. Walls can settle differently depending on wooden houses, and the foundations are on layered or heaving soils. In all these cases, consider installing rafter systems of this type.

System for houses with two internal load-bearing walls

If the house has two load-bearing walls, install two rafter beams, which are located above each of the walls. The beams are laid on the intermediate load-bearing walls, the load from the rafter beams is transferred to the beams through the racks.

In these systems ridge run they don’t install it: it provides spacer forces. The rafters in the upper part are connected to one another (cut and joined without gaps), the joints are reinforced with steel or wooden plates, which are nailed.

In the upper non-thrust system, the pushing force is neutralized by the tightening. Please note that the tightening is placed under the purlin. Then it works effectively ( top diagram on the image). Stability can be provided by racks, or joints - beams installed diagonally. In the spacer system (in the picture it is below) the crossbar is a crossbar. It is installed above the purlin.

There is a version of the system with racks, but without rafter beams. Then a stand is nailed to each rafter leg, the other end of which rests on the intermediate load-bearing wall.

Fastening the rack and tightening in the rafter system without a rafter purlin

To fasten the racks, 150 mm long nails and 12 mm bolts are used. Dimensions and distances in the figure are indicated in millimeters.

Reading time ≈ 10 minutes

The most common option in the construction of private houses is a gable roof, assembled with your own hands from the mauerlat to the ridge. Below in this article you will find drawings and photos, and detailed step-by-step instruction will help you understand them. You will also learn about what height the ridge should be and how it depends on the functionality attic space, learn to calculate the thickness and pitch of the rafter system.

Classic gable roof

What kind of roofs are there?

Main types of roofs of private houses

In order to clearly imagine what a gable roof is, look at what other options are used in the construction of private houses. And this is not all, but the most popular:

- the simplest coating option for construction in the private sector. Mainly used for country houses and utility rooms.
Gable - the most common option for country houses. Despite its apparent simplicity, this type is very practical and beautiful in execution.
Hip - more suitable for houses with large area. This design can withstand very strong wind loads, even storms, due to its streamlined shape.
Half-hip - this option is made more for beauty, since it is a prototype of a gable roof with cut corners from the ends of the ridge.
Tent - pyramidal shape is suitable for square buildings. In essence, this is a prototype of a hip roof.
Vaulted - rarely used for residential construction, although it is no exception.

For a rectangular house with an area of 60 to 100 m2, the option with two slopes can be called the most suitable - it is simple to implement and inexpensive to implement. In addition, you can arrange not only an attic, but also an attic.

Stages of construction of a gable roof

Now let's figure out how to build gable system roofs in a private house. There are several stages in this process and we will consider each of them separately.

Calculation of the rafter system taking into account the current loads

You don’t have to use formulas for calculations if you don’t make roofs in the future and just download the program (http://srub-banya.by/programs/raschet_stropil.exe). By opening the downloaded file, you will be taken to a page with a menu - it is located in a horizontal line at the top.

Main operating loads:

Snow cover.
Wind pressure.

In addition to the main loads, there are also secondary or “default” ones, these are:

Weight of roofing material.
Weight of insulation (if provided).
Own weight of the rafter system.

Values:

S – load value in kg/m2.
µ is the coefficient corresponding to the slope angle of the slope.
Sg is the snow load standard in kg/m2.

The slope of the slope is expressed in degrees and is designated by the symbol α (alpha). To determine the value of α, you need to divide the height H by half the span L. Below is a table with the results of determining the main slopes.

In cases where:

α≤30⁰, µ=1;
α≥60⁰, µ=0;
30°<α<60°, µ = 0,033*(60-α).

Distribution of snow loads across Russia

The map shows eight snow regions, and the Sg value for each is calculated in kPa, converted to kg/m2:

I - 0.8 kPa = 80 kg/m2;
II - 1.2 kPa = 120 kg/m²;
III - 1.8 kPa = 180 kg/m²;
IV - 2.4 kPa = 240 kg/m²;
V - 3.2 kPa = 320 kg/m²;
VI - 4.0 kPa = 400 kg/m²;
VII - 4.8 kPa = 480 kg/m²;
VIII - 5.6 kPa = 560 kg/m².

For the map given above, Appendix 5 of SNiP 2.01.07-85 “Loads and Impacts” is required. Now let’s make a test calculation for Ivanovo (this is the IV district on the map), the value is 240 kg/m².

This means: H/L=2.5/3.5=0.714

According to the table α=35⁰. Considering that 30°<α<60°, вычисление µ делаем по формуле µ = 0,033·(60-α)=0,033*(50-35)=0,825. Следовательно, S=Sg*µ=240*0,825=198 кг/м², что и есть максимально возможной снеговой нагрузкой.

Wind loads

On steep roofs, where α > 30°, the slopes have a large windage. For flat roofs, where α< 30° увеличена турбулентность.

The average value of wind load Wm at height Z above the ground surface is calculated using the formula Wm=Wo*K*C.

In this formula the meaning is;

Wo – wind pressure;
K – coefficient of change in wind pressure relative to height;
C – aerodynamic coefficient.

Wind loads in the territory of the former USSR

Wind pressure standards by region

Coefficient value

Let's perform a conditional calculation . The aerodynamic coefficient C can be from -8, when the wind undermines the roof, to +0.8 with a large windage (the wind presses on the slope). Taking into account the conventionality of the calculation, we take C = 0.8.

In the same Ivanovo district we take a house where h=6m (α=35⁰). This is region II, where Wo= 30 kg/m², the coefficient is less than 10, which means K=1.0. Therefore: Wm=Wo*K*C=30*1*0.8=24 kg/m².

Roof weight

The weight of the roof varies depending on material

Weight of all components

The conditional calculation for the same house using cement-sand tiles will be:

And here is the calculation for the lightest roofing material, metal tiles:

We calculate the rafter system

In this case, we will be guided by GOST 24454-80 for coniferous species.

Section width (according to board thickness), B	Section height (across the board width), H
16	75	100	125	150	—	—	—	—	—
19	75	100	125	150	175	—	—	—	—
22	75	100	125	150	175	200	225	—	—
25	75	100	125	150	175	200	225	250	275
32	75	100	125	150	175	200	225	250	275
40	75	100	125	150	175	200	225	250	275
44	75	100	125	150	175	200	225	250	275
50	75	100	125	150	175	200	225	250	275
60	75	100	125	150	175	200	225	250	275
75	75	100	125	150	175	200	225	250	275
100	—	100	125	150	175	200	225	250	275
125	—	—	125	150	175	200	225	250	—
150	—	—	—	150	175	200	225	250	—
175	—	—	—	—	175	200	225	250	—
200	—	—	—	—	—	200	225	250	—
250	—	—	—	—	—	—	—	250	—

We take an arbitrary section width and determine the height:

H ≥ 8.6*Lmax*√(Qr/(B* Rbending)), where slope α< 30°,

H ≥ 9.5*Lmax*√(Qr/(B*Rbending)), where Rbending and slope α > 30°.

Values:

H—section height, cm;
Lmax - rafter leg of maximum length, m;
Qr - distributed load per meter of rafter leg, kg/m;
B - section width, cm.

For softwood lumber Rbending:

I grade – 140 kg/cm²;
II grade – 130 kg/cm²;
III grade – 85 kg/cm².

Now let’s check whether the deflection falls within the standard, which for all materials under load should not exceed the value L/200 (L is the length of the working section of the leg). The indicator must correspond to the inequality: 3.125*Qr*(Lmax)³/(B·H³) ≤ 1.

Meaning:

Lmax—working section of the leg of maximum length, m;

B—section width cm;

H—section height, cm.

We are counting on the same house in Ivanovo, taking into account the conditions where:

slope α=35⁰;
rafter pitch A=0.8 m;
working section of the leg Lmax=2.8 m;
1st grade pine beam R bend = 140 kg/cm2;
cement-sand tiles 50 kg/m2.

In the table above we calculated that with such materials the total load is Q = 303 kg/m².

We calculate the load per linear meter of the leg: Qr=A*Q= 0.8*303=242 kg/mline.
Let's take a board thickness of 5 cm and calculate the cross-section in height: this means: H ≥ 9.5*Lmax* √(Qr/B*Rbend), since the slope α>30°. H≥9.5*2.8*√(242/5*140)=15.6 cm. Based on the table, the board with the nearest cross-section will be 5×17.5 cm.
We check that the inequality is satisfied: 3.125*Qr*(Lmax)³/B*H³≤1 or 3.125*242*(2.8)³*5*(17.5)³=0.61<1.

As a result, we received a cross-section of rafters for constructing a roof of 50x175 mm with a pitch of 80 cm.

Mauerlat installation

Mauerlat on a brick wall

To build a gable roof yourself, you cannot do without a Mauerlat, which is the basis of the rafter system. If we are talking about a residential building, then they usually use timber with a cross-section from 50×150 mm to 150×200 mm (the thicker the wall, the larger the cross-section of the beam in width). The board or beam is mounted on load-bearing walls and fixed with anchors. If we take into account that the Mauerlat will withstand the entire rafter system with associated loads, then its installation will directly affect the mechanical strength of the entire roof. Below is a video that shows how to install a Mauerlat on the walls of a block house.

Video: Installing the Mauerlat

Assembling the rafter system

Rafter legs are easier to assemble on the ground

It is most convenient to assemble a structure such as rafters (2 legs plus additional elements) on the ground, as in the photo above, and not on the roof, in order to then raise it with blocks or simply ropes, but this is not a requirement. Above you could find out how to make calculations for such a system taking into account all the loads, therefore, you already know what section of boards you will need, what the height of the ridge will be and the step size. At the top, the boards are butted together, and the ridge beam is installed only after the outer rafters have been installed.

A system without an overhang, where the legs are fixed with different fasteners

For systems with an overhang, the fasteners are also different

Above you see two diagrams showing rafter systems without an overhang and with an overhang, but the most important thing is to pay attention to the method of fastening, or rather, to the fastening itself. This can be a steel corner (preferably reinforced), short pieces, tightening boards, nails, screws and staples. This is a very important point, since during turbulence the roof can be undermined, and under lateral load it can be overturned, although the result in both cases will be equally disastrous. After installing the side rafters, fix the ridge beam, checking each leg vertically with a level.

Watch the video, which explains some of the nuances of installation, but do not forget that each master may have his own methods, and if you hear or see inconsistencies with your ideas, then this is quite normal.

Video: Installation of the rafter system

Roof

Installation of ceramic tiles

Further work on the installation of the rafter system depends on what is provided in the attic and what roofing material will be used. For example, if you want to arrange an attic there, then it is quite natural that you cannot do without insulation and waterproofing. The heating system, or rather the presence or absence of a chimney, as well as ventilation, will also play a certain role.

Depending on the choice of roofing material, the sheathing is made. That is, it can be intermittent, as in the top photo, or continuous, if you decide to make a roof from bitumen shingles. Also, for roofs they sometimes provide for the installation of a heating cable against icing, and it can be mounted not only from the outside, but also from the inside, laying it under the roof.

Conclusion

You, I hope, have understood how to make a gable roof with your own hands - the most important thing is the correct calculations of the pitch, cross-section of the rafter legs and slope. If you are interested in certain points, such as fastening the Mauerlat, rafters or roofing work, then these are topics for separate articles, which you can also read on our website.

When constructing one-story houses, a roof with two slopes is very popular. This is due to the speed of construction of the structure. In this parameter, only a single-pitched roof can compete with a gable roof. The design of the gable rafter roof is not too complicated. And you will successfully master this work on your own.

Design of a gable roof truss system

A gable roof consists of two inclined surfaces that have a rectangular shape. Thanks to this, precipitation, which is represented by rain and melt water, drains from the roof naturally. The gable roof has a rather complex structure. It consists of the following structural units: mauerlat, rafter system, fillies, ridge, roof overhang, bed, struts, tie-downs, sheathing and racks:

Mauerlat. This element performs the functions of transferring and distributing the load created by the rafter system onto the load-bearing walls of the house. To make the Mauerlat, timber is used, which has a square cross-section - from 100 by 100 to 150 by 150 mm. It is better to use coniferous wood. The timber is placed around the perimeter of the building and secured to the external walls. For fastening, special rods or anchors are used.
Rafter leg. Rafters form the main frame of any roof. In the case of a gable roof, they form a triangle. The rafters are responsible for the uniform transfer of loads to the Mauerlat. First of all, those that arise from precipitation, wind and the weight of the roof itself. For the manufacture of rafters, boards are used that have a cross-section of 100 by 150 or 50 by 150 mm. Choose a rafter pitch of about 60-120 cm, depending on the type of roofing material. When using heavy coverings, place rafter legs more often.
Horse. This element connects the two slopes at the top of the roof. The ridge is formed after connecting all the rafter legs.
Fillies. They act as a continuation of the rafters and form the overhang of the gable roof. It is customary to install fillies if the rafter legs are very short and do not allow the formation of an overhang. To make this structural unit, take a board that has a smaller cross-section than the rafter. The use of fillies facilitates the construction of the rafter system, as it allows the use of short rafters.
Eaves. This part of the design of the gable roof truss system is responsible for draining water from the walls during rain and at the same time preventing them from getting wet and quickly collapsing. The overhang from the wall, as a rule, protrudes 400 mm.
Sill. It is located on the inner wall and serves to evenly distribute the load from the roof pillars. To make the bed, a timber is used, which has a cross-section of 150 by 150 or 100 by 100 mm.
Racks. These vertical elements are responsible for transferring the load from the ridge to the interior walls. To create this element, prepare a beam that has a square section of 150 by 150 or 100 by 100 mm.
Struts. They are needed to transfer loads from the rafters to the load-bearing walls. The struts and ties form a strong structure called a truss. Such a device is designed to withstand loads over large spans.
Puff. This structural unit, together with the rafters, forms a triangle. It does not allow the rafters to move in different directions.
Lathing. This structure consists of boards and bars. They are attached perpendicular to the rafters. Lathing is necessary to evenly distribute the weight of the roof covering and the loads created by weather conditions onto the rafters. In addition, sheathing is required to fasten the rafters together. When arranging a soft roof, moisture-resistant plywood should be used to create sheathing rather than boards and bars.

Types of gable roof rafter system

There are gable rafter systems with hanging and layered rafters. Ideally, the design contains a combination of them. It is customary to install hanging rafters if the external walls are located at a distance of less than 10 m. Also, between them there should no longer be walls that divide the space of the residential building. The design with hanging rafters creates a bursting force transmitted to the walls. It can be reduced if you make a tie made of wood or metal and place it at the base of the rafters.

The rafters and the tie form a rigid geometric figure - a triangle. It is not capable of deforming under loads that appear in any direction. The tightening will be stronger and more powerful if it is positioned higher. The tie beams are the floor beams. Thanks to their use, the hanging rafter system of a gable roof serves as the basis for arranging the attic floor.

In their design, layered rafters have a support beam, which is placed in the middle. It is responsible for transferring the weight of the entire roof to the intermediate columnar support or middle wall located between the outer walls. It is recommended to install layered rafters if the external walls are located at a distance of more than 10 m. If there are columns instead of internal walls, you can alternate between layered and hanging rafters.

DIY gable rafter system

The roof must be strong to withstand various loads - precipitation, gusts of wind, the weight of a person and the roofing itself, but at the same time light so as not to put much pressure on the walls of the house. A properly constructed gable rafter roof evenly distributes the load across all load-bearing walls.

Calculation of a gable roof

The choice of slope for a gable roof will depend on the material you have chosen for laying on the roof and architectural requirements:

When erecting a gable roof, remember that it must slope at an angle of more than 5 degrees. It happens that the roof slope reaches 90°.
For areas with heavy rainfall, and when the roofing does not fit tightly, steep slopes are made. In this situation, the angle should be 35-40° so that precipitation does not linger on the roof. But such an angle does not allow building a living space in the attic. The solution will be a broken roof structure. It will have a flat upper part, and a sharp slope at the lower part.
In regions with strong gusts of wind, flat roofs are installed. If constant winds prevail in the area, then make a slope of 15-20° for high-quality protection of the roofing.
It is best to choose the middle option. Make sure the gable roof is not too steep. But the slope should also not be very gentle.
When choosing a large roof angle, its windage increases, and, accordingly, the price of the gable roof rafter system and sheathing increases. After all, such a slope entails an increase in the roof area and, accordingly, in the amount of necessary material - construction and roofing.

When purchasing materials for constructing a gable roof, it is useful to calculate its area:

Find the area of one slope of the structure, and then double the result.
Ideally, the slope is an inclined rectangle that is placed along a long load-bearing wall. To determine the area of the slope, multiply its length by its width.
The length of the slope is equal to the length of the wall. In addition, the length of the roof overhang above the gable is added to the length. Remember that there are tabs on both sides.
The width of the slope is the length of the rafter leg. The length of the roof overhang above the load-bearing wall is added to it.

In order to correctly design the structure, it is recommended to carry out an accurate calculation of the rafter system of a gable roof, including determining the loads and characteristics of the rafters:

When erecting a roof for a standard building that has one floor, the design load on the roof will consist of two values. The first of them is the weight of the roof, the second is the load from external factors: precipitation and wind.
Calculate the weight of the roof by adding up the weight of each layer of the “pie” - thermal insulation, vapor barrier and waterproofing materials, rafter system, sheathing and the roofing material itself. Calculate the weight per 1 m2.
Increase results by 10%. You can also take into account the correction factor. In our case K=1.1.
If you plan to change the roof structure over time and increase its angle of inclination, then factor in a safety margin into the calculation. Immediately take higher loads than those you received at the time of calculation. It is recommended to start from a value of 50 kg per 1 m2.
When calculating the load exerted by atmospheric phenomena, take into account the climatic features of the area where the building is located. When making this calculation, take into account the slope of the slope. If the gable roof forms an angle of 25 degrees, then assume a snow load of 1.
If the roof is equipped with a greater slope - up to 60 degrees, the correction factor reaches 1.25. Snow loads for angles greater than 60 degrees are not taken into account.
The rafters transfer the entire load from the created structure to the load-bearing walls. Therefore, their parameters must be taken accordingly. Select the cross-section and leg length of the rafters, depending on the current load on the roof and the angle of the slope. Increase the obtained values by 50% to ensure a high safety margin.

Mauerlat installation methods

The construction of any roof begins with the installation of the Mauerlat:

If logs or beams were used to build the walls, then the top beam will act as a Mauerlat, as shown in the photo of the gable roof rafter system.
If you used brick to build the walls, then wall up metal rods into the masonry. They must have a thread cut for attaching the Mauerlat. Install rods every 1-1.5 m. Choose rods with a diameter of at least 10 mm. Lay waterproofing between the masonry and the mauerlat.
For walls made of ceramic or foam concrete blocks, pour concrete on top. Be sure to make the layer reinforced. It should have a height of approximately 200-300 mm. Be sure to attach metal rods that have threads to the reinforcement.
For the Mauerlat, use a beam that has a cross-section of 15 by 15 cm. It will act as a kind of foundation for the rafter system.
Place the Mauerlat on the top edge of the wall. Depending on its design, the Mauerlat can be laid along the outer and inner edges. Do not place it close to the very edge, otherwise the wind may blow it off.
It is recommended to place the Mauerlat on top of the waterproofing layer. To connect all parts into one, use bolts and metal plates.
To avoid sagging, make a lattice from racks, struts and crossbars. To do this, take boards measuring 25x150 mm. The angle between the strut and the rafter leg should be as straight as possible.
If you use a rafter leg that is too long, install another support. She should rest on the bed. Each element is associated with two neighboring ones. The result is a stable structure around the entire perimeter of the roof.

Fastening rafter legs

The best option for a gable roof rafter system is a combination of inclined and hanging rafters. This design allows you to create a reliable gable roof and reduce the cost of building materials. Consider the following recommendations when working:

Use only the highest quality wood as material. Beams that have cracks and knots should absolutely not be used.
The rafters have standard dimensions - 50x150x6000 mm. When beams are longer than 6 m, it is recommended to increase the width of the board so that the beams do not break under their own weight. Take boards 180 mm wide.
First make a template for the rafter leg. Attach the board to the floor beam and the end of the ridge beam. Having outlined two lines, saw off the board along them. The template is ready.
Cut the rafters according to this template. After this, make the top cut on them.
Take the resulting workpiece and bring it to the floor beam to mark the bottom cut in place.
Install all rafters. At the same time, remember that after installing one leg, you must immediately install the opposite one. This way you will quickly remove the lateral loads on the ridge beam.
If the slope is too long, then standard boards will not be enough to make a rafter leg. In this case, you can join two boards together. To do this, sew on them a piece of wood of a similar cross-section. It should have a length of 1.5 - 2 meters. According to the gable roof rafter system diagram, the joint should always be at the bottom. Install an additional stand under it.
Attach the rafter leg to the ridge beam using nails. To attach the rafters to the floor beam, use self-tapping screws. Metal mounting plates are also suitable. In addition, a few nails are added.
If you are building a structure entirely from hanging rafters, then skip the next stage. When erecting a structure with layered rafters, you need to think about the supports that are installed on the floor. To reduce the deflection of the rafters, correctly calculate the location of such supports.
If you are building a gable mansard roof, the intermediate posts will become the frame for the side walls.
When performing this work, maintain a certain pitch of the beams. Set its size at the design stage.
After installing the rafters, attach the ridge. It is placed along their upper edge. Metal corners or brackets are used for fastening. And the most popular are bolts.

Rigidizing the structure

After installing the gable roof rafter system, strengthen it using the technology presented below:

For small buildings, such as saunas, cottages, utility buildings, and roofs with a simple hanging rafter system, connect each pair of rafters from below using a tightening, and from above using a crossbar.
For large buildings that are also lightweight, choose a light roof. The walls must support it.
If the house is 6-8 m wide, then the structure should be strengthened. Place the support in the middle. Such racks are called headstocks. Place them at each pair of rafter legs.
If the span of the walls reaches 10 meters, then reinforcing beams will be needed. The struts act as additional support for the rafter legs for tightening. They are attached to each rafter - closer to the ridge or in the middle of the rafter leg. Fasten them to the lower end of the headstock and to each other, as shown in the video about the gable roof rafter system.
In situations with long roofs, the gable beams should be relieved. This is done by installing braces. The top end should rest against the corner of the gable. The lower one is mounted on the central floor beam. For fastening, use a beam that has a large cross-section. This way you can prevent them from breaking if there are strong gusts of wind.
In areas where winds prevail, the rafters must be resistant to such influences. Strengthen them by installing diagonal braces. The boards are nailed from the bottom of one rafter to the middle of the next.
For greater rigidity, when creating the most critical fastenings, it is better not to use nails. Use linings and metal fastening methods for this. Nails will not be able to provide high-quality fastening, since the wood can dry out after some time.

Lathing of the rafter system

The final stage of installing a gable roof rafter system is the creation of sheathing. It is on this that you will lay the roofing covering. Carry out the work in the following sequence:

Select dry timber for sheathing. There should be no cracks or knots on it. Nail the beams from below. Attach two boards near the ridge so that there are no gaps. The sheathing must withstand the weight of the upper roofing material and not bend under the weight of the workers.
If you are installing a soft roof, make two layers of sheathing. One is sparse, the second is continuous. The same applies to roll roofing. To begin, place boards parallel to the ridge beam that are 25 mm thick and no more than 140 mm wide. A small gap is allowed - no more than 1 cm. Lay a continuous layer on top. To do this, it is better to use roofing plywood, slats or boards of small thickness. After this, check that there are no errors left on the sheathing - irregularities and knots. Also check that there are no nail heads sticking out.
Place one layer of timber under the metal tiles. It should have a cross section of 50 by 60 mm. Proceed in the same way when using slate or steel roofing sheets. Maintain a step between the beams, depending on the roofing you choose - from 10 to 50 cm. Hammer the nails closer to the edges of the board, and not in the middle. Drive the hats in deep. This way they won’t be able to damage the roof later. If you are making sheathing for metal tiles, then remember that the connection of the timber at the same level must fall on the rafter.

When you have installed and strengthened the rafter system of the gable roof, you can begin installing the roofing pie. Place thermal insulation material, a layer of vapor barrier and waterproofing between the rafters. When using insulation in slabs, calculate in advance the pitch of the rafters for its installation. At the final stage, attach the roofing material.

There are a lot of variations in the design of the truss structure of a gable roof. Its appearance will largely depend on how the attic space will be heated or cold, on the presence of load-bearing partitions, the choice of roofing material and, of course, on the taste preferences of the developer. Despite the variety of roof structures (rafter system and roofing pie), the basic installation rules remain unchanged.

The main stages of installing a gable roof

Gable roof projects

Before starting the installation of the roof, it is necessary to draw the external shapes of the future frame, indicating its configuration and height, so that in total the gable roof looks proportional in relation to the overall structure, in a word - to clearly imagine the structure of the gable roof rafters. This can be done in any way convenient for you, the main thing is to maintain the scale for a real vision of the prospects. From experience we can say that the optimal roof height is considered to be 1/3 of the length of the house. Here we implement our ideas regarding a straight or broken slope, branching in the main lines (Fig. 1), residential or non-residential attic space and the type of roof itself, it can be hanging or layered. The latter option is more often used when constructing gable roofs, since it is more practical and economical in terms of lumber consumption.

After you have decided on the external appearance and functional purpose of the structure, you need to draw a diagram of the rafter system and make its layout in projection. This is necessary in order to calculate the required amount of material for constructing the roof.

The expenditure item of the total budget for roof installation will largely depend on how complete and rational the calculations are made. For example, if you know in advance that you will need N number of linear meters of timber, then when cutting you need to take into account the standard length of the lumber and the size of the rafter leg. As a rule, long structural elements have to be made into joints, so without proper cutting, you can get an inflated percentage of waste.

Despite the fact that gable roofs are considered the most convenient and economical in terms of laying roofing, it is not superfluous to calculate the amount of sheet or piece material. Since the installation of each of them has its own characteristics, the need for overlap, the number of ridges or waves, technical features (one-sided capillary groove), etc., when calculating the total surface area, it is necessary to take into account all these subtleties.

The height of the slate wave and the thickness of the sheet also matter if slate is chosen as a roofing material.

According to GOST 30340-95, 8 wave and 7 wave slates are produced with the following parameters: wave height h - 40 mm, wave pitch (distance between adjacent ridges) - 150 mm, and sheet thickness - 5.2 or 5.8 mm.

Example of consumables calculations

Ideally, when the installation of a gable roof is carried out according to the project, a selection of all structural elements is made, indicating the length and quantity of each position. Using a rational cutting system, the volumes are summed up by:

Lumber (m.p.)
Insulation (m2)
Vapor barrier membrane (m2)
Roofing covering (quantity in pieces, m2)

For clarity of calculations, we will take as a basis a house with specific dimensions

Width(s) – 5 m
Length (h) – 8 m
Apex angle () – 1200
Slope angle (A, C) – 300

We start by calculating the height of the roof, it is calculated as follows

h = ½ x a/ tg /2 = 0.5 x 5/ 1.73 = 1.44 mm

the length of the rafter (AB) according to the right triangle theorem will be equal to the product of ½ the width of the house divided

by sine of ½ vertex angle

L(AB) = 1/2 x a / sin /2 = 1/2 x 5 / 0.87 + 0.5 = 2.87 m

To the resulting length, do not forget to add the length of the eaves overhang; it is determined in the range of 0.5 ÷ 0.8 m. Therefore, the final size of the rafter leg will be equal to 2.87 + 0.5 ÷ 0.8 = 3.37 ÷ 3.87 m (let's stick to the 3.5m option)

S over. roof = a x L(AB) x 2 = 5 x 3.5 x 2 = 35 m2

This is not a total figure for the amount of roofing material that will be needed to cover the roof. To it you will need to add the percentage of waste based on the cutting according to the roof configuration. For each option it will be individual, so the final result will be known after specific calculations.

Lumber for sheathing is also easy to calculate. The pitch between the battens (m) is taken to be 300 mm. Total

M = L(AB) / m x b = 3.5 / 0.3 x 8 x2 = 187 l.m.

We calculate the board for the rafters in the same way. The pitch between the rafters is set, it can vary from 600 to 1000 mm, the cross-section of the board, the weight of the roofing pie are taken into account, and not the least role is played by the multiplicity, which is dictated by the width of the heat-insulating mats and the size of sheets of moisture-resistant plywood or OSB boards when making a continuous sheathing.

All other elements are calculated according to the given scheme.

Set of tools for constructing a roof

Once you have completely decided on the designs of the rafter system and the roofing pie, you can adjust the classic list of tools that you will need to build the roof. It is very convenient to have a belt for tools when working at the top, so they will always be in one place and at hand. Its kit should include:

Roulette
Pencil or marker
Lace (beat)
Hammer
Roofing shears
Putty knife
Roofing knife
Construction tape
Hacksaw
Screwdriver with screw attachment

In some cases, mastic-based adhesives and polyurethane foam may be needed.

Some devices greatly simplify the installation process, such as templates and slats with markings.

Roofing details

It is also worth paying attention to the so-called roofing details, which the developer often does not pay attention to, but they also affect the functionality and durability of the roofing system. The use of low-quality self-tapping screws (without the manufacturer's mark and with a thickness of EPDM gaskets less than 2 mm) leads to roof leaks. Poor paint coating on fittings can deteriorate over time and ruin the appearance of the roof. Another element that is important when constructing a roof is snow retainers; their absence increases the risk of an avalanche of snow falling from the roof. In turn, this may lead to damage to the drainage system, buildings or cars under the roof. The next problem that worries developers is the problem of condensation, which is associated with insufficient ventilation of the under-roof space. To improve air exchange, it is necessary to provide for the installation of ventilation outlet elements in the roof surface; they allow you to ventilate the under-roof space more intensively, and therefore avoid the problem of condensation.

They forget to prescribe antiseptic compounds as an item in the expenditure item, without which it is impossible to imagine modern construction made of wood.

Gable roof rafter system. Installation and its features.

The installation begins with the installation of a support beam - Mauerlat. It is installed on load-bearing walls and secured using pre-built anchor bolts or metal studs. The accuracy of installation of the entire rafter structure depends on how smoothly the Mauerlat is mounted. His straightforwardness

checked using a level; if necessary, leveling is done using linings or trimming off protruding parts. The flatness of the support beam allows you to use one template to make all the table legs on the ground, rather than having to adjust each one in place. It is recommended to carry out the support of the rafters on the mauerlat using one of the methods indicated in Figure 3.

It is highly undesirable to cut on a mauerlat or on a ridge run; this can reduce the load-bearing capacity of the supporting elements.

If the project provides for a ridge girder, and this is a more reliable option, the next step is to install a beam at the top point of the gables. Fastening units A and B in Fig. 1 are made according to the diagrams shown in Fig. 4

The ridge girder is made from 50x200-250 mm boards, the ends of the beams are treated with an antiseptic compound and wrapped with waterproofing material, the end part is left open for air access. Assembling a rafter structure with a ridge girder is much easier than without it. The fact is that the presence of a longitudinal beam allows you to install a pair of rafters separately, which saves time and labor costs.

Roofing pie device

Upon completion of the installation of the rafter system, they proceed to laying the vapor barrier layer. The rolled material is rolled out parallel to the ridge girder and attached to the rafters on the inside of the roof. Butt joints are made overlapping and sealed with tape.

From above, the space between the rafters is filled with insulation. To ensure protection of thermal insulation from moisture due to possible roof leaks or condensation forming on the inner surface of the roof covering, under-roof waterproofing is installed. It is nailed to the outside of the rafters with nails or staples and secured with counter battens.

Next, the sheathing is installed; its design is selected depending on the roofing material. With the help of counter battens and sheathing, a ventilated gap is created, this ensures the air-dry condition of all roof materials.

Laying the roof covering is the final stage in the construction of the roof. It is applied according to the manufacturer's instructions. At the end of the main work, they begin to assemble and install drainage systems, ventilation, snow retainers and ladders for roof maintenance.