Rafters made of boards 40x100 for metal tiles. Distance between wooden rafters under metal tiles

The roof structure is one of the main enclosing elements of the building, to quality characteristics which has quite stringent requirements.

One of the most common materials for roof sheathing is metal tiles, which is made from thin steel, aluminum or copper sheets.

The elements are equipped on top polymer coating, which protects metal from aggressive external influences.

Externally, metal tiles are similar to ceramic ones, but they are more durable. This material is used for coating pitched roofs, the slope of which must be at least 14 degrees.

This is a national team frame construction roofs consisting of many wooden or metal parts. She rests on load-bearing walls, which are a reliable basis for all overlying elements. The rafter system serves as a kind of skeleton on the basis of which the roof is made, as well as the laying of the roofing finishing layer.

Rafter system

Components rafter roof, and their main characteristics:

  • Mauerlat. Timber from coniferous, which is the connecting element between the rafters and the underlying structures. It has a square cross-section with a side of 100 or 150 mm. Mauerlat is laid along load-bearing wall along its entire length. With the help of a Mauerlat, the loads from the roof are evenly distributed throughout the building.
  • Sill. Beam having square section similar to the Mauerlat. It is laid transversely to load-bearing walls, as it serves to redistribute the load from the roof racks.
  • Rafter leg. From these elements, the main triangular roof structure is created, which experiences the full brunt of external atmospheric influences (rain, wind, snow, hail, etc.).
  • Rack. Vertical connecting elements that distribute compressive loads from the ridge unit over the entire area of ​​the load-bearing walls. Executed from square beams, the edge length of which is determined by calculation.
  • Puff. It is the final horizontal element of the triangle of rafter legs, preventing them from creeping away under the pressure of external loads and the roof’s own weight. Used in systems with hanging rafters.
  • Struts. They perceive and redistribute bending loads from the ridge unit.
  • Lathing. Consists of boards, bars or plywood sheets (in case of subsequent installation bitumen shingles), which are located at a right angle relative to the rafter legs, being an additional rigidity element.
  • . The junction of two roof slopes.
  • Overhang. Roofing element, protruding beyond the load-bearing wall structures at a distance of about 0.4 m. Its purpose is to limit the penetration of moisture to the walls.
  • Fillies. These elements are attached to the ends of the rafters if they are not long enough to create an overhang.

Types of pitched roofs

Depending on the number of inclined planes, roofing structures can be divided into:

In private housing construction, the option most often used is gable roof, since he has a number of advantages. These include:

  1. Practicality. Gable roof has a significant angle of inclination, due to which rainwater does not accumulate on its surface, and snow and wind loads are distributed most optimally.
  2. Simplicity of device and operation. The assembly and joining of two pitched elements is much simpler than that of complex roofing structures. In addition, repairing such a roof will also be simple.
  3. Aesthetics. Roof with gable construction fits seamlessly into the surrounding infrastructure.
  4. Reliability(if done correctly).
  5. Democratic price constituent materials.

Types of pitched roofs

Gable roof - rafter system for metal tiles

Frame made of rafters under a gable roof made of metal tiles no significant differences from structures with other covering roofing materials.

But, due to the fact that thin metal sheets have small specific gravity , the rafters will experience less constant load.

This makes it possible to reduce the value of their cross section, due to which you will be able to save a lot on the purchase of wooden materials.

Optimal for roofing under metal tiles The tilt angle must be at least 14 degrees.

For a roof with two pitched elements, the following are used: Frame arrangement options:

Layered rafters for metal tiles.

In this case, 2 load-bearing rafter legs are fastened together using bed(horizontally) and racks(vertical). The beam is laid parallel to the Mauerlat element, while taking on some of the force influences. The rafter system for metal tiles takes on itself bending loads only, which significantly affects the selection of the design cross section. This system can be used for buildings with large and small spans.

Types of rafters

Hanging rafters.

Unlike layered systems, this option has two rafter legs are fastened together only in the ridge knot. In this case, significant pushing forces arise on the load-bearing elements, which limits the use hanging rafters only for buildings with a span of no more than 6 m. In some cases, it is possible to install an additional connecting element - a tie, which takes on part of the thrust loads.

They can be made of wood or metal, and can also be installed below (they act as load-bearing beam) or at the top of a triangular structure. It is worth considering that the higher the tightening is located, the greater the force it will absorb.

NOTE!

To ensure high-quality tightening performance, care must be taken about the reliability of fastening with load-bearing rafter legs.

Combined option

Used to create original roofing structure. Includes elements of both hanging and layered systems.

How to calculate the angle of rafters?

To implement gable roof need to know a few geometric values ​​of the building, namely:

  • Half span width - L;
  • Distance from load-bearing wall to roof ridge (or height support post) – H.

Standard formula: α = arctan(L/H)

Where α is the desired roof inclination angle.

Knowing this value, you can calculate the length of the carrier rafter leg:

l = H/sinα.

Where l is the length of the rafter element.

Rafter angle

How to calculate the load?

To implement correct selection roof frame parts required calculate temporary and permanent load values, acting on its structural elements.

The permanent load includes the weight of all elements, as well as the mass of the elements themselves. load-bearing elements and lathing.

Temporary loading options include force effects from wind, snow cover, rain masses, as well as the weight of a person (to take into account options for subsequent repairs).

Dead load calculation

Weight of the roofing pie.

It is determined by adding the masses of all its elements, namely steam, hydro and thermal insulation, as well as roofing from metal tiles. In this case, the weight of one linear meter (can be found in the regulatory documentation) is multiplied by the value of its length.

Weight rafter system.

Determined by adding the weight values ​​of the sheathing, rough flooring, and load-bearing frame. The mass of each element is calculated by the formula:

M = V * p,

Where V is the volume of the element, calculated depending on the geometric characteristics of the cross section and length of the element;

P – Density of wood used (depending on the species).

Total constant load = weight of the rafter system + weight of the roofing pie.

Live Load Calculation

Conducted in accordance with regulatory documentation ( SNiP 2.01.07-85 “Loads and impacts” or Eurocode “Actions on structures” part 1-4).

To determine the value of wind exposure, the roof structure is conventionally divided by height into several parts. For each of them, the wind load value is calculated. To obtain the total wind pressure they must be summed.

Formula for calculation:

Wm=Wo×k×c,

Where Wm is the value of the wind load;

Wo – normative meaning wind pressure determined from zoning maps;

k – wind pressure coefficient (determined depending on the height according to regulatory documentation);

c – aerodynamic coefficient (for a gable roof – 0.8).

Determined by the formula:

S = µ×So;

Where So is the standard value of the snow load, determined from the zoning map.

µ is a coefficient that is determined depending on the angle of inclination of the roof:

  • For α≤30 deg. — µ=1
  • For α≥60 deg. — µ=0
  • For 30≤α≤60 deg. — µ=0.033×(60-α)

Snow load areas

How to choose timber and calculate the pitch of rafters for metal tiles?

Determining the cross-sectional value of the beam of the rafter element is carried out in several stages.

Calculation of the load distributed on each linear meter designs:

Qр = L×Q;

L – Rafter pitch.

The L value is calculated as follows:

The length of the roof slope is divided by the expected pitch of the structures (for convenience, it is most often taken equal to 1). Then 1 is added to the resulting value. The resulting value reflects the number of rafters that need to be installed on one pitched roof surface. On last stage The value of the axial distance between the rafter elements is determined by dividing the length of the roof slope by the number of rafters.

The distance between the rafters for metal tiles is a standard step of 0.6-0.95 m.

Rafter pitch

Then we determine the maximum working area of ​​the rafter leg (Lmax). Let's move on to calculating the cross section. To do this, we find its height using the formula:

H ≥ 8.6*lmax * sqrt(Qp/(b*r)), with roof slope α<30 град;

H ≥ 9.5*lmax * sqrt(Qp/(b*r)), with roof slope α≥30 degrees;

Where b is the width of the cross section,

r – the value of the standard resistance of wood to bending loads (determined according to regulatory documentation depending on the type of wood).

To simplify calculations, you need to use the standardization table for rafter elements (GOST 24454-80 “Softwood lumber. Dimensions").

If the inequality is not met, it is necessary to increase the value of the geometric characteristics of the section and repeat the calculation.

What is the difference between the rafter system for cold and warm roofs?

The main difference between these two roofs is the system of supporting the rafter elements. In the case of a warm attic, the main supporting element is the mauerlat, as well as the supporting beam system. In a cold roof, rafters are installed directly onto load-bearing walls.

Installation of rafters under metal tiles

All roofing installation work is carried out at a fairly high altitude. To minimize the risk of falls and to make working at heights much easier, you can assemble the frame of the supporting rafter system on the ground.

To do this, you need to create a template from the boards, according to which further assembly will be carried out.

It is produced in several stages:

  • The boards are lifted above the walls of the building, leveled, and then are fastened using a nail.
  • Level the angle of the boards in accordance with the project, by lowering and raising them. The elements are fixed.
  • The result should be a structure resembling the shape of the future rafter system, made in accordance with the calculated geometric dimensions of the roof.
  • The template is lowered to the ground, according to which the finishing elements are fixed together. More details in the video below.

Then you should take care of installing the supporting element - the Mauerlat. As mentioned earlier, it is laid on load-bearing walls in the longitudinal direction. Fastening is done using studs (on an armored belt or masonry) or using wire rod (for buildings with a small roof height).

CAREFULLY!

When using a pin connection, the connecting elements no need to wall up tightly into the wall. They should protrude from the wall by 30-40 mm, since the nut will be screwed onto the studs.

The next step is to create ridge girder, serving as a supporting part for the entire structure of the gable roof. It is made from timber or hewn logs. If the span of the building is no more than 6 m, it can be supported without additional supporting elements.

Otherwise, construction trusses must be used for installation.

After installing these elements, you can lift and install the main rafter element assembled according to the template. Fastening to the Mauerlat can be done in 2 ways:

Rigid connection. This is done using corners and beams. Less commonly used are fastenings by sawing on rafter legs, followed by fixation with nails or staples.

Features: in addition to the main connection, it is necessary to tie the rafters to the wall using anchors or a wire structure.

Sliding. It is based on the creation of a hinged connection. It is made by joining elements using cuts. The elements are connected by a metal embedded part with holes for bolts, or 2 nails, which must be driven in at an angle.

Wooden trusses must be installed in a certain sequence. First, the outer trusses located at the ends of the building are installed. Then a cord or rope is stretched between them, with the help of which the verticality of their installation is checked. Next, under the cord, further installation of rafter structures is carried out in accordance with the specified design step.

Installation. Part 2

Creating a roof from metal tiles is a rather labor-intensive process that requires certain skills and a trained hand. Therefore, to carry out proper installation, you must at least work under the supervision of a competent specialist.

Useful video

Video instructions for self-installation of rafter legs:

The more carefully the preliminary calculations are made, and in particular, the more correctly the pitch of the rafters for metal tiles is determined, the more reliable the frame of the future roof will probably be.

If, during calculations, the load on the rafter structure is determined incorrectly, or the parameters of the rafters are underestimated, in the future such errors can cause damage to the roofing or change the shape of the rafter legs, as well as lead to the collapse of the rafter base.

When calculating the roof structure, it is also necessary to calculate the distance that will be between the rafters. Determining these parameters is not particularly difficult if you correctly use the general methods for calculating such distances, accepted among specialists.

Calculation of the pitch between rafters

The gap between the rafter legs is usually called the pitch of the rafters or the step of the rafter legs.

Usually in a roof structure this distance should not be more than one meter, the permissible minimum is 60 centimeters.

In order to calculate the required number of rafters for a given roof length and, accordingly, determine the pitch of the rafters, proceed as follows:

  1. The length of the slope is measured along the eaves of the roof.
  2. The resulting value is divided by the unit of measurement, in this case by the selected rafter pitch. For example, when the rafter pitch is 1 meter, the length is divided by 1, if the pitch is 80 cm, then by 0.8, etc.
  3. At the next stage of calculations, one is added to the result obtained, then this value is rounded up. This is how you find out the required number of rafters that are supposed to be installed on one roof slope.
  4. The total length of the slope will need to be divided by the resulting number of rafters - as a result, we obtain the value of the interaxial gap between the rafters, which is called the rafter pitch.

For example, with a roof slope length of 27.5 m and a rafter pitch 1 m long, the calculation will be as follows:

Accordingly, 29 rafters will be needed for the roof slope.

So, 95 cm is the gap between the axes of the rafters installed on the roof slope.

However, the general calculation methodology does not take into account the features of certain roofing materials.

The most common types of coverings can be considered in detail - how, according to the recommendations of professionals, the pitch of the rafters should be selected when constructing a rafter system, depending on the selected type of roofing material.

Rafter spacing for metal roofing

When building country houses, the most common roofing material is metal tiles.

Metal tile roofing looks like clay tile flooring, but has multiple advantages over clay roofing..

  • As for installation, sheet metal tiles are much more technologically advanced, and the time spent on roof construction is significantly reduced.
  • This roofing material is much lighter in weight than tiles made from natural clay: the difference in weight is 1 sq.m. will be about 35 kg - depending on the thickness of the natural tiles.

With such a reduction in the weight of the roof deck, it is possible to significantly reduce the requirements for many parameters when calculating the rafter system for metal tiles. For example, you can increase the installation pitch of the rafters, reduce their thickness, and reduce the cross-section of the sheathing bars for metal tiles.

To cover the roof with metal tiles, the gap between the rafters is determined in the region of 60-95 cm with a cross-section of the structural element of 150 by 50 mm.

According to experts, a thickness of 15 cm will be sufficient for insulation placed between the rafters, and this thickness will be enough for good thermal insulation of the roof. But for reliability, it is better to choose insulation with a thickness of 20 cm. With this indicator, the cross-section of the rafter leg also increases to 20 cm.

To improve ventilation of the space that is intended to be filled with insulation, when installing rafters, a series of holes with a diameter of 10 mm are drilled in them (rafters) near the top edge.

In general terms, the rafter structure for metal tiles is fundamentally no different from any other. Perhaps its only peculiarity is that the upper support of the rafters is placed not on the ridge beam, that is, on the side, but on the ridge girder - from above.

Between the joined wooden parts, a free zone is created at the top, which ensures air circulation, which reduces the risk of condensation forming under the roofing - this is important for the metal surface of the material.

When installing the roof of a wooden house, which involves replacing the mauerlat with an upper log crown, an incorrect calculation of the rafter pitch will make any changes almost impossible, since notches are usually made in the crown in order to increase the reliability of fastening.

Elements for strengthening the rafter system

A fastening element such as rafter tightening is used when the roof is erected using hanging rafter elements.

To tighten the rafters, a horizontal beam or log is used, attached to the base of the rafter legs - this can significantly reduce the horizontal pushing forces that act on the walls of the building.

A tie can also be installed above the base of the rafters, but with this method it is made somewhat more powerful, which subsequently has a beneficial effect on the durability of the roof.

The filly is an extension of the rafter leg, which is attached to the leg with ordinary nails. The rafter fillet is made from a board half as high and thick as the rafter leg. Moreover, its length is approximately 1-1.2 meters, of which one half forms an overhang, the second provides attachment to the rafters.

When installing a rafter system under metal tiles, or under any other roofing material, special corners for fastening rafters are used to fix its elements. The advantages of such an element are the provision of high load-bearing capacity, as well as the ability to carry out fastening without the use of special tools. The wooden structures of the rafter system and the corners are connected using screws or nails.

Rafter processing

There are two main problems for which rafters need impregnation:

  1. Protection against fungus and insects. If the rafters are not treated with antiseptics in a timely manner, there is a high risk of grinder beetles appearing in the wood, which will gradually gnaw away at the wooden parts of the roof.
    Fungus and mold pose no less danger to rafters. Improper installation of roofing materials can lead to such undesirable results as mold and fungal colonies, and these factors destroy rafters even faster than insects.

Having correctly calculated all the necessary parameters of the future rafter system, you can begin its construction, maintaining confidence in its future reliability and durability.

A gable roof or gable roof is a roof with two slopes, i.e. having 2 inclined surfaces (slopes) of a rectangular shape.

Due to its design features, the frame of a gable roof ideally combines simplicity of design and maintenance with reliability and durability. These and many other parameters make the construction of a gable roof a practical and rational solution for private and commercial housing construction.

In this article, we will look at how to make a rafter system for a gable roof with your own hands. For effective perception of the material, it is presented in the form of step-by-step instructions from A to Z, from selection and calculations, to installation of the Mauerlat and sheathing under the roof. Each stage is accompanied by tables, diagrams, drawings, drawings and photos.


The popularity of the house roof is due to a number of advantages:

  • design variability;
  • simplicity in calculations;
  • naturalness of water flow;
  • integrity of the structure reduces the likelihood of leaks;
  • efficiency;
  • preserving the usable area of ​​the attic or the possibility of arranging an attic;
  • high maintainability;
  • strength and wear resistance.

Types of gable roof

The installation of a gable roof truss system depends, first of all, on its design.

There are several options for gable roofs (types, types):

The most common roof installation option due to its simplicity and reliability. Thanks to symmetry, a uniform distribution of loads on the load-bearing walls and mauerlat is achieved. The type and thickness of the insulation does not affect the choice of material.

The cross-section of the beam makes it possible to provide a reserve of bearing capacity. There is no possibility of rafters bending. Supports and struts can be placed almost anywhere.

An obvious drawback is the impossibility of arranging a full-fledged attic floor. Due to sharp corners, “dead” zones appear that are unsuitable for use.

The arrangement of one angle of more than 45° leads to a reduction in the amount of unused area. There is an opportunity to make living rooms under the roof. At the same time, the requirements for calculations increase, because the load on the walls and foundation will be distributed unevenly.

This roof design allows you to equip a full second floor under the roof.

Naturally, a simple gable rafter roof differs from a broken roof, not only visually. The main difficulty lies in the complexity of the calculations.

Design of a gable roof truss system

Building a roof of any complexity with your own hands requires knowledge of the purpose of the main structural elements.

The locations of the elements are shown in the photo.


  • Mauerlat. Designed to distribute the load from the rafter system onto the load-bearing walls of the building. To arrange the Mauerlat, a timber made of durable wood is selected. Preferably larch, pine, oak. The cross-section of the timber depends on its type - solid or glued, as well as on the expected age of the structure. The most popular sizes are 100x100, 150x150 mm.

    Advice. For a metal rafter system, the Mauerlat must also be metal. For example, a channel or an I-profile.

  • Rafter leg. The main element of the system. To make rafter legs, a strong beam or log is used. The legs connected at the top form a truss.

The silhouette of the roof truss determines the appearance of the structure. Examples of farms in the photo.

The parameters of the rafters are important. They will be discussed below.

  • Puff- connects the rafter legs and gives them rigidity.
  • Run:
    • Ridge run, is mounted at the junction of one rafter to another. In the future, the roof ridge will be installed on it.
    • Side purlins, they provide the truss with additional rigidity. Their number and size depend on the load on the system.
  • Rafter stand- vertically located beam. It also takes on part of the load from the weight of the roof. In a simple gable roof it is usually located in the center. With a significant span width - in the center and on the sides. In an asymmetrical gable roof, the installation location depends on the length of the rafters. If there is a broken roof and one room is arranged in the attic, the racks are located on the sides, leaving free space for movement. If there are supposed to be two rooms, the racks are located in the center and on the sides.

The location of the rack depending on the length of the roof is shown in the figure.

  • Strut. Serves as a support for the stand.

Advice. Installing the brace at an angle of 45° significantly reduces the risk of deformation from wind and snow loads.

In regions with significant wind and snow loads, not only longitudinal struts are installed (located in the same plane as the rafter pair), but also diagonal ones.

  • Sill. Its purpose is to serve as a support for the rack and a place for attaching the strut.
  • Lathing. Designed for movement during construction work and fixing roofing material. Installed perpendicular to the rafter legs.

Advice. An important purpose of the sheathing is to redistribute the load from the roofing material to the rafter system.

Having a drawing and diagram indicating the location of all the listed structural elements will help in the work.

Advice. Be sure to add information about the passage of the ventilation shaft and chimney to the gable roof rafter system diagram.

The technology of their installation is determined by the type of roof.

Selection of material for rafters

When calculating the material for a gable roof, you need to choose high-quality wood without damage or wormholes. The presence of knots for beams, mauerlat and rafters is not allowed.

For sheathing boards, there should be a minimum of knots, and they should not fall out. The wood must be durable and treated with the necessary preparations that will increase its properties.

Advice. The length of the knot should not exceed 1/3 of the thickness of the timber.

Calculation of the rafter system of a gable roof

Calculating the material parameters is an important step, so we present the calculation algorithm step by step.

It is important to know: the entire rafter system consists of many triangles, as the most rigid element. In turn, if the slopes have different shapes, i.e. are an irregular rectangle, then you need to divide it into separate components and calculate the load and amount of materials for each. After calculations, summarize the data.

1. Calculation of the load on the rafter system

The load on the rafters can be of three types:

  • Constant loads. Their action will always be felt by the rafter system. Such loads include the weight of the roof, sheathing, insulation, films, additional roofing elements, finishing materials for. The weight of the roof is the sum of the weight of all its constituent elements; such a load is easier to take into account. On average, the constant load on the rafters is 40-45 kg/sq.m.

Advice. To make a safety margin for the rafter system, it is better to add 10% to the calculation.

For reference: The weight of some roofing materials per 1 sq.m. presented in the table

Advice. It is desirable that the weight of roofing material per 1 sq.m. roof area did not exceed 50 kg.

  • Variable loads. They act at different times and with different strengths. Such loads include: wind load and its strength, snow load, precipitation intensity.

In essence, the roof slope is like a sail and, if you take into account the wind load, the entire roof structure can be destroyed.

The calculation is carried out according to the formula: wind load is equal to the regional indicator multiplied by the correction factor. These indicators are contained in SNiP “Loads and Impacts” and are determined not only by the region, but also by the location of the house. For example, a private house surrounded by multi-story buildings experiences less load. A detached country house or cottage experiences increased wind loads.

2. Calculation of snow load on the roof

The roof calculation for snow load is carried out according to the formula:

The total snow load is equal to the weight of the snow multiplied by the correction factor. The coefficient takes into account wind pressure and aerodynamic influence.

The weight of snow that falls on 1 square meter. roof area (according to SNiP 2.01.07-85) is in the range of 80-320 kg/sq.m.

Coefficients showing the dependence on the slope angle are shown in the photo.

Nuance. When the slope angle is over 60 ° the snow load does not affect the calculation. Because the snow will quickly slide down and will not affect the strength of the beam.

  • Special loads. Accounting for such loads is carried out in places with high seismic activity, tornadoes, and storm winds. For our latitudes, it is enough to make a safety margin.

Nuance. The simultaneous action of many factors causes a synergy effect. This is worth considering (see photo).

Assessment of the condition and load-bearing capacity of walls and foundations

It should be borne in mind that the roof has significant weight, which can cause damage to the rest of the building.

Determining the roof configuration:

  • simple symmetrical;
  • simple asymmetrical;
  • broken line

The more complex the shape of the roof, the greater the number of trusses and rafter elements needed to create the necessary safety margin.

The angle of inclination of a gable roof is determined primarily by the roofing material. After all, each of them puts forward their own demands.

  • soft roof - 5-20°;
  • metal tiles, slate, corrugated sheets, ondulin - 20-45°.

It should be noted that increasing the angle increases the area of ​​space under the roof, but also the amount of material. What affects the total cost of work.

Nuance. The minimum angle of inclination of a gable roof must be at least 5°.

5. Calculation of rafter pitch

The pitch of the gable roof rafters for residential buildings can be from 60 to 100 cm. The choice depends on the roofing material and the weight of the roof structure. Then the number of rafter legs is calculated by dividing the length of the slope by the distance between the rafter pairs plus 1. The resulting number determines the number of legs per slope. For the second, the number must be multiplied by 2.

The length of the rafters for the attic roof is calculated using the Pythagorean theorem.

Parameter "a"(roof height) is set independently. Its value determines the possibility of arranging a living space under the roof, the convenience of being in the attic, and the consumption of material for the construction of the roof.

Parameter "b" equal to half the width of the building.

Parameter "c" represents the hypotenuse of the triangle.

Advice. To the obtained value you need to add 60-70 cm for cutting and moving the rafter leg beyond the wall.

It is worth noting that the maximum length of the timber is 6 m.p. Therefore, if necessary, the timber for the rafters can be spliced ​​(extension, joining, joining).

The method of splicing rafters along the length is shown in the photo.

The width of the roof rafters depends on the distance between opposite load-bearing walls.

7. Calculation of the rafter cross-section

The cross-section of the rafters of a gable roof depends on several factors:

  • loads, we have already written about it;
  • type of material used. For example, a log can withstand one load, timber - another, laminated timber - a third;
  • rafter leg lengths;
  • the type of wood used in construction;
  • distances between rafters (rafter pitch).

You can determine the cross-section of the beam for the rafters, knowing the distance between the rafters and the length of the rafters using the data below.

Rafter cross-section - table

Advice. The larger the installation pitch of the rafters, the greater the load on one rafter pair. This means that the cross-section of the rafters needs to be increased.

Dimensions of lumber (timbers and boards) for a gable rafter system:

  • thickness (section) of the Mauerlat - 10x10 or 15x15 cm;
  • the thickness of the rafter leg and tie is 10x15 or 10x20 cm. Sometimes a beam of 5x15 or 5x20 cm is used;
  • run and strut - 5x15 or 5x20. Depending on the width of the foot;
  • stand - 10x10 or 10x15;
  • bench - 5x10 or 5x15 (depending on the width of the rack);
  • thickness (section) of the roof sheathing - 2x10, 2.5x15 (depending on the roofing material).

Types of gable roof rafter system

For the roof structure under consideration, there are 2 options: layered and hanging rafters.

Let's consider each type in detail in order to make an informed choice.

Hanging rafters

They are used for roof widths of no more than 6 lm. Installation of hanging rafters is carried out by attaching the legs to the load-bearing wall and the ridge girder. The design of hanging rafters is special in that the rafter legs are under the influence of a bursting force. Hanging rafters with a tie installed between the legs reduce its impact. The tie in the rafter system can be wooden or metal. Often the ties are placed at the bottom, then they play the role of load-bearing beams. It is important to ensure that the tie is securely attached to the rafter leg. Because a bursting force is also transmitted to it.

Advice.
The higher the tightening is located, the greater strength it should have.
If the tightening is not installed, the load-bearing walls may simply “move apart” from the pressure created by the rafter system.

Layered rafters

They are used for arranging roofs of any size. The design of layered rafters provides for the presence of a beam and a stand. The bench lying parallel to the Mauerlat takes on part of the load. Thus, the rafter legs are, as it were, inclined towards each other and supported by a stand. The rafter legs of the layered system work only in bending. And the ease of installation also tips the scales in their favor. The only drawback is the presence of a stand.

Combined

Due to the fact that modern roofs are distinguished by a wide variety of shapes and complexity of configurations, a combined type of rafter system is used.

After choosing the type of rafter system, you can accurately calculate the amount of materials. Write down the calculation results. At the same time, professionals recommend drawing up drawings for each roof element.

Installation of a gable roof rafter system

After the gable roof rafters have been calculated, installation can begin. We will divide the process into stages and give a description of each of them. The result will be a kind of step-by-step instructions containing additional information on each stage.

1. Attaching the Mauerlat to the wall

The beam is installed along the length of the wall on which the rafters will rest.

In log houses, the role of the mauerlat is played by the upper crown. In buildings built from porous material (aerated concrete, foam concrete) or brick, the Mauerlat is installed along the entire length of the load-bearing wall. In other cases, it can be installed between the rafter legs.

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Since the length of the Mauerlat exceeds the standard dimensions of lumber, it has to be spliced.

The connection of the Mauerlat to each other is done as shown in the figure.

How to connect the Mauerlat?

The beams are cut only at an angle of 90°. Connections are made using bolts. Nails, wire, and wooden dowels are not used.

How to attach the Mauerlat?

The Mauerlat is installed at the top of the wall. The installation technology provides several ways to attach the Mauerlat:

  • strictly in the center of the load-bearing wall;
  • with a shift to one side.

Advice.
The Mauerlat cannot be placed closer than 5 cm to the outer edge of the wall.

To protect the timber for the Mauerlat from damage, it is laid on a layer of waterproofing material, which most often is ordinary roofing felt.

The reliability of the Mauerlat fastening is an important aspect of construction. This is due to the fact that the roof slope is like a sail. That is, it experiences strong wind load. Therefore, the Mauerlat must be firmly fixed to the wall.

Methods for attaching the Mauerlat to the wall and rafters

Anchor bolts. Ideal for monolithic structures.

Wooden dowels. Used for log houses and beams. But, they are always used with additional fasteners.

Staples.

Stud or fittings. It is used if the cottage is built from porous materials (aerated concrete, foam concrete).

Sliding mount (hinge). Tying in this way allows for the displacement of the rafter legs when the house shrinks.

Annealed wire (knitting, steel). Used as an additional mount in most cases.

2. Manufacturing of trusses or pairs

Installation is carried out in two ways:

  • installation of beams directly on the roof. It is not used often, since it is problematic to carry out all the work, measurements, and trimming at height. But it allows you to completely do the installation yourself;
  • assembly on the ground. That is, individual elements (triangles or pairs) for the rafter system can be assembled below and then raised to the roof. The advantage of such a system is faster performance of high-altitude work. The disadvantage is that the weight of the assembled truss structure can be significant. To lift it you will need special equipment.

Advice. Before assembling the rafter legs, you need to apply markings. It is very convenient to use templates for these purposes. The rafter pairs assembled according to the template will be absolutely identical. To make a template, you need to take two boards, the length of each of which is equal to the length of one rafter, and connect them together.

3. Installation of rafter legs

The assembled pairs rise to the top and are installed on the Mauerlat. To do this, you need to make a gash at the bottom of the rafter legs.

Advice. Since the slots on the Mauerlat will weaken it, you can only make cuts on the rafter leg. To ensure that the cut is uniform and fits tightly to the base, you need to use a template. It is cut out of plywood.

Methods of fastening the rafter leg are shown in the figure.

You need to start installing rafter pairs from opposite ends of the roof.

Advice. To correctly install the rafter legs, it is better to use temporary struts and spacers.

A string is stretched between the fixed pairs. It will simplify the installation of subsequent rafter pairs. It will also indicate the level of the ridge.

If the rafter system is mounted directly on the roof of the house, then after installing the two outer rafter legs, the ridge support is installed. Next, the halves of the rafter pair are attached to it.

It is worth noting that the opinions of professionals differ on this issue. Some advise using a staggered fastening pattern, which will allow the increasing load to be distributed more evenly on the walls and foundation. This order involves installing one rafter in a checkerboard pattern. After part of the rafter legs is installed, the missing parts of the pair are mounted. Others insist that it is necessary to mount each pair in a sequential manner. Depending on the size of the structure and the configuration of the truss, the rafter legs are reinforced with supports and racks.

Nuance. Additional structural elements are connected using cutting. It is preferable to fix them with construction staples.

If necessary, you can lengthen the rafter leg.

Methods for splicing rafter legs are shown in the photo.

Advice. The method by which the mauerlat is lengthened (cut at 90°) cannot be used in this case. This will weaken the rafter.

4. Installing the ridge of a gable roof

The roof ridge unit is made by connecting the rafter legs at the top.

Roof ridge structure:

  • Method without using a support beam (see figure).

  • Method using rafter beams. Timber is needed for large roofs. In the future, it can become a support for the rack.
  • Method of laying on timber.

  • A more modern version of making a ridge knot can be considered the method shown in the photo.

  • Cutting method.

After the rafter system is installed, we perform major fastening of all structural elements.

5. Installation of roof sheathing

The sheathing is installed in any case, and is designed for more convenient movement along the roof during work, as well as for fastening roofing material.

The sheathing pitch depends on the type of roofing material, for example:

  • for metal tiles - 350 mm (the distance between the two lower boards of the sheathing should be 300 mm).
  • for corrugated sheets and slate - 440 mm.
  • We lay a continuous sheathing under the soft roof.

Rafter system of a gable roof with an attic - video:

Conclusion

As you can see, despite its apparent simplicity, the installation of a gable roof rafter system contains many pitfalls. But, based on the recommendations given, you can easily build a reliable structure with your own hands.

Correct installation of sheathing under metal tiles is the key to high-quality installation of roofing material. Let us highlight the main points on choosing the type and pitch of the sheathing, as well as calculating the required number of boards and their size in the case of installing a metal roof.

Counter-lattice is an important element of the roofing “pie”

Before installing the sheathing, make sure that the roofing “pie” is made correctly. In particular, is there a ventilation gap between the waterproofing film and the board on which the metal tiles will be installed. After laying the waterproofing membrane along the rafters, a block measuring 50x50 mm (counter-lattice or counter-batten) is nailed along the rafters, with the help of which air will circulate under the roofing material. The pitch of the counter-lattice is equal to the span width of the rafter system, usually 700 - 800 mm.

Roofing "pie" for metal tiles

  1. Rafters
  2. Waterproofing (diffusion membrane)
  3. Counter-lattice (bar 50x50 mm)
  4. Lathing for metal tiles
  5. Metal tiles
  6. Vapor barrier
  7. Sheathing starting board
  8. Cornice strip
  9. PVC ventilation tape or aluminum mesh
  10. Kapelnik
  11. Gutter holder
  12. Frontal board

The main purpose of the counter-lattice is to preserve the roofing material and the wooden roof structure by “weathering” excess condensation formed under the metal tiles. The rule is valid for both a cold roof and an attic one.

Types of lathing

A board with dimensions of 25 (30) x 100 mm is used as a base for metal tiles. Its thickness is not of fundamental importance (25 or 30 mm), since the weight of a metal roof does not exceed 7 kg/m2. The material will also easily withstand snow loads during winter operation. The main thing is that the thickness of each board should be the same or with a slight deviation of 2-3 mm. This condition will ultimately allow you to obtain a flat slope plane.

For metal tiles, three types of lathing can be distinguished: sparse(or stepper) solid And combined. The first type is the most common, as it is used on various roof shapes with a slope of more than 20 degrees. The distance between the centers of the boards in this case is equal to the wavelength of the metal tile.


Sparse lathing

For flat structures (14-20°), continuous sheathing is used. Let us remind you that minimum permissible roof slope for metal tiles- 14 degrees. Please note that despite the name “solid”, it is not recommended to lay the boards closely: it is necessary to leave a technical gap of 2-3 cm.


Continuous sheathing

The combined installation scheme for metal tiles includes the first two types. Stepping is performed over the entire roof area, except for additional roof components: the junction of the roof with a pipe or wall, valleys. It is recommended to install continuous sheathing in these areas of the roof.


Continuous sheathing: on the left - the valley assembly, on the right - the junction of the metal tile to the pipe

A continuous sheathing also needs to be installed:

Lathing pitch for Monterrey and other types of metal tiles

To determine the pitch of a sparse (not continuous) sheathing, it is necessary to know the wavelength of the metal tile. For the Monterrey profile, the distance between adjacent boards will be 350 mm.

The sheathing pitch is calculated from the center (axis) to the center of the board. The step between the starting and second board is usually considered to be from the bottom edge of the starting board to the center of the second.


Sheathing pitch for metal tiles Monterrey

The distance between the starting sheathing board and the second board is 300 mm, while the subsequent sheathing pitch for Monterrey metal tiles is 350 mm. This is due to the need to extend the roof by 50 mm (see image).

The offset of the roof relative to the first sheathing board for most types of metal tiles is 5 cm.

Here are the data for the most popular types of profiled roofing to determine the pitch of the board for metal tiles:

Metal tile profiles Lathing pitch, mm
from the bottom of the 1st to the center of the 2nd board from center to center of subsequent boards
Monterrey 300 350
SuperMonterrey 300 350
Maxi 350 400
Cascade 300 350
MaxiCascade 350 400
Classic 300 350
Kvinta (Kvinta plus) 300 350
Country (Quinta) 300 350
Quadro profi 300 350
Kamea (Cameo) 300 350
Finnera 300 350
Adamante 300 350
Decorrey 300 350
Spanish Dune 300 350
Andalusia 350 400
Joker 350 400

As you can see, most profiles come down to two types of sizes between adjacent boards: 350 and 400 mm, which are also relevant for modular metal tiles with hidden fastening (for example, Andalusia or Spanish Dune).

You cannot increase the gap between the sheathing (for example, make a distance through a wave), because deformation of the roofing profile due to snow mass or other mechanical influences is possible.

Lathing scheme for metal tiles from manufacturers

When installing a roof, it is very important to have reliable and authoritative information on the technical aspects of installing each structural element. Manufacturers of metal tiles, as a rule, offer their instructions describing the correct design of their products. Let us give examples with lathing schemes for the most famous brands of metal roofing presented on the domestic market.


Starting sheathing and installation of end strip from Grand Line

Please note that to securely fasten the end strip, you should install the support board above the level of the ordinary sheathing. Its height should be approximately equal to the height of the tile profile.

Offers similar schemes Metal Profile, especially focusing in its instructions on the installation of sheathing in areas of the valley, roof fencing and snow retention elements. In all of the above cases, continuous sheathing is required.

Continuous sheathing in the valley area

Manufacturing and trading company Unikma in its instructions for installing a metal profile, it pays special attention to fastening roofing screws if the lathing pattern is incorrect (see image below).


Fasteners for continuous sheathing and lathing with imprecise pitch

Thus, we can conclude that a continuous deck under a metal roof is undesirable. You should also carefully observe the distance between the boards.

Products for treating wooden roof structures

An important step before installing the rafter system and sheathing is the treatment of wooden raw materials with special means that give additional durability to individual components and the roof as a whole. An important point before choosing an antiseptic is not only the type of wood, but also the general climatic conditions of the location of the construction site. Experienced builders know that in hot climates wood must be protected from fire, and in humid climates - from water.

The main types of such funds include:

  • fire retardants (fire retardants);
  • bioprotective;
  • water-repellent;
  • protect against mold and mildew;
  • universal means.

One of the most popular and universal antiseptics is "Senezh", which, thanks to its chemical properties, penetrates deeply into the layers of wood, protecting rafters and sheathing from premature rotting, insect damage and other factors that destroy wood.

Wooden roof elements can be treated by impregnating the surface with a regular brush. A more effective and widespread way of treating wood is to apply an antiseptic using spray devices of a mechanical or automatic operating principle.

Before starting the processing process, the wood must first be cleared of debris and dried.

To fasten the sheathing board to the counter-batten, galvanized nails are most often used, less often - wood screws. It is better to use screw or razor type nails. The optimal nail length is 70 mm.

Each board at the intersection with the counter-lattice is connected to it with two nails in the upper and lower parts at a distance of about 20 mm from the edge of the board.


Fastening sheathing boards under metal tiles

If the standard length of the board (usually 6 meters) is not enough, it is better to place the joint of the boards for building up the sheathing in the center of the counter-batten bar (see figure). Knowing the dimensions of the boards, the distance between them, the width and height of the roof slope, you can easily calculate the amount of material for sheathing under a metal tile roof.

The problems of building low-rise buildings have been solved with the help of metal tiles for a long time. The combination of steel endurance with lightness and efficiency gives the material a great advantage over its rivals. Large sheets are laid much faster, and their service life is longer than other materials for similar purposes. You can cover the roof and install the rafter system under the metal tiles yourself if you know the structure of the gable roof, the features of the rafter system and the methods of laying the roofing material, taking into account its characteristics.

Description of metal tiles

Metal tiles can be called one of the rolled steel products. In general, the material is sheet steel, which is profiled both horizontally and vertically. As a result of this process, transverse and longitudinal waves are formed on the surface, making the material look like ceramic tiles. On the outside of the sheet there is a colored polymer film designed to perform a protective and decorative function.

Disadvantages and their elimination

Despite the visual similarity to ceramic tiles, the standard disadvantages of the material remained unchanged. The metal heats up very quickly when exposed to sunlight and cools easily when the air temperature drops. The sound insulation coefficient is relatively low, since metal surfaces freely transmit sound waves. In addition, the metal is capable of collecting drops of condensate due to different thermal properties with the contacting elements of the frame.

These are quite significant shortcomings, but the problem of their existence is easily solved with the correct assembly of the rafter system and roofing pie. If the installation of the rafter system is carried out according to all the rules in compliance with technological requirements, then the installation of the roofing material will proceed without complications.


To reduce the impact of metal imperfections on the roof structure and prevent premature wear of the roof, it is necessary to correctly compose the roofing cake.

All responsibility in this regard falls on the rafter system, which is assigned the following functions:

  • Retention of layers of roofing cake located on top of the rafters, below these elements and between them.
  • Creating conditions for better ventilation, preventing the formation of condensation and creating channels for the removal of moisture.
  • Formation of supports located in the same plane for laying roofing material.

In other words, the rafter system is a kind of skeleton that is necessary for the normal functioning of the roof. Consequently, the shortcomings of the metal coating can be eliminated by choosing the right scheme for installing the “skeleton” under the metal tile.

Rafter system for metal tiles - rafter pitch

Metal tiles can be seen on any buildings: both residential and non-residential. Metal “scales” look good on gazebos, verandas and bathhouses.

The presence of insulation is determined by the functional purpose of the building, and the structure of the rafter system largely depends on this:

  • The frame of an insulated roof contains three different layers of insulation and a mandatory ventilation circuit.
  • A cold roof consists of a ventilation circuit and one layer of insulation.

A gable roof under metal tiles with insulation is necessary if a living space is to be built in the attic. When calculating such a rafter system, the size of the insulation is taken into account so that it fits tightly into the spaces between the rafter legs.


A roof without insulation is erected over buildings, the stay in which does not take much time.

Also, a roof frame under metal tiles without insulation is erected when the ceiling is insulated. An example is the roof over a bathhouse or a residential building, the attic of which is not intended for use. In this case, laying insulation between the ceiling beams will be more effective.

The roof frame for metal tiles can be made of rolled metal or lumber. The first option has similar characteristics to a metal coating, but for private houses it is recommended to use wood. This material is more convenient to use for a private developer who has decided to independently build a rafter system for metal tiles. Firstly, it is easier to make frame elements from wood and assemble them into a single structure. Secondly, wooden products are warmer and comply with environmental requirements and standards.

The advantage of a gable roof

The simplest version of the rafter system for metal tiles is a gable structure. Due to the similarity of the shapes of the slopes and sheets of roofing material, ideal conditions for installation are created. A hip structure, or any complex roof for that matter, requires a lot of effort and time. In addition, complex structures require increased consumption of roofing material due to the complexity of the cut.

The manufacturer's instructions for laying metal tiles indicate the optimal roof parameters. In particular, we are talking about the slope of the slopes, which should be 12-15 degrees. A smaller inclination angle requires enhanced waterproofing; on steeper slopes it is necessary to increase the fastening elements. Both situations lead to an increase in the roof construction budget.


The number of laid rows of metal tiles directly depends on the size of the sheet and the area to be covered. In most cases, the material is installed in one row so that water does not leak into the transverse seams. On the roofs of private houses, sheets 4-4.5 meters long are most often used, although many manufacturers offer services for cutting sheets into appropriate elements. This greatly simplifies the installation of metal tiles on individually sized slopes. To determine the required length of the sheet, sum up the length of the slope and the length of the eaves overhang, which is 40-60 cm.

The metal tiles are laid on the sheathing attached to the rafter system. A gable roof has only vertical and horizontal lines, so laying sheets with similar edges can be done without much difficulty. A properly constructed rafter system allows you to install sheathing and lay roofing material quickly and without problems.

Frame and rafter options

The design of the rafter system is determined by the number of layers of the roofing pie. Consequently, a more complex insulated option requires elements that a cold roof can do without.

For the rafter system of a gable roof made of metal tiles, it is necessary to install a row of several pairs of rafters, the design of which is determined by the features of the main structure.

To manufacture the rafter frame of a gable roof, the following methods are used:

  • Using layered technology. In this case, it is necessary to provide strong supports for the rafter legs at the top and bottom. Its use is allowed only if there is an internal load-bearing wall or powerful columns replacing it. A layered rafter system can only be installed in cases where the racks under the ridge girder are installed on sufficiently strong ceiling beams or reinforced concrete slabs.
  • Using hanging technology. The rafters of such a system require mandatory support for the lower heel. The upper heels rest on each other in pairs. A hanging rafter system is installed in the absence of an internal load-bearing partition.

Construction of a frame for an insulated roof

The presence of insulation in the roofing pie requires choosing the correct pitch of the rafters for the metal tiles, and arranging the rafter structure so that the heat-insulating layer does not lose its qualities. This can happen as a result of the insulation getting wet, since water serves as a good conductor of heat waves.

Thermal insulation material gets wet in the following cases:

  • Household fumes rising upward penetrate the thermal insulation from the inside.
  • The temperature difference between the street and the attic contributes to the formation of condensation.
  • Failure to comply with roof installation technology leads to the formation of leaks, which are observed during snowmelt and heavy rainfall.

To prevent unpleasant situations from occurring, you need to properly lay the roofing cake, distribute it over the roof and securely fix it to the rafters. In addition, the rafter system under the metal tile must form ventilation channels that allow air flow to wash the thermal insulation layer and the inner layer of the metal tile.


Installing lathing and counter-lattice allows you to create channels that facilitate regular ventilation and removal of condensation from under the roof space. This extends the service life of both the roof and the rafter system.

In cross-section, the insulated roof from the side of the finished room looks like this:

  • Material used for finishing work inside the attic.
  • Internal sheathing on which a vapor barrier layer is attached.
  • Directly a vapor barrier layer, which is an obstacle to household fumes.
  • Rafter legs, in the spaces of which there are slabs of heat-insulating material. Moreover, to form a ventilation gap, the thermal insulation must be slightly thinner than the width of the rafters. If the insulation lies flush with the rafters, then additional sheathing should be nailed to create the necessary gap.
  • The waterproofing layer is laid directly on the rafters or on the counter-lattice, if there was a need to install it. The fact is that waterproofing in the form of polyethylene film cannot be in contact with the insulation in order to prevent the formation of moisture. When using a diffuse membrane, a counter-lattice is not needed, since this waterproofing material allows moisture to pass out, but does not let it back in.
  • External sheathing, a necessary element for fixing waterproofing material, creating a ventilation duct and laying metal tiles.
  • The roofing material itself is metal tiles.


It is not recommended to use bitumen-based roll materials as a waterproofing layer. Heating of such material and the roof is accompanied by the release of substances, due to which mutual destruction of both materials occurs.

Based on the above, the conclusion suggests itself that the installation of a gable roof made of metal tiles with insulation involves the use of a three-layer cake and two ventilation circuits when using the classic version of waterproofing. The diffuse membrane included in the roofing pie allows the installation of three layers of insulation and one ventilation duct. The basis for fastening all layers is the rafter system, which is responsible for holding the roofing material and the snow load.

In most cases, rafters for metal tiles are made from boards with a cross-section of 5*10 cm or 5*15 cm, subject to the standard pitch of the rafter legs when installing the roof.

Installation of a rafter system for a cold roof

A cold roof implies the absence of insulation, therefore, there is no need to use materials to protect it. But waterproofing cannot be neglected; it will protect the wooden rafter system from leaks. In addition, there must be ventilation between the waterproofing layer and the metal tile in any case.

In cross-section, the cold roofing pie has the following composition:

  • Rafters.
  • Waterproofing.
  • Lathing.
  • Roofing material.


Regardless of the presence of insulation, the sheathing is laid in a special way. The distance between the elements is determined by the gap between the transverse steps of the metal tile.

The first element of the lath should be slightly larger than ordinary laths.

The given examples of cold and insulated roofing are a general recommendation. In practice, each individual case requires certain calculations with specific data.