The roof is gable, what step to take for boys. Calculation of the distance between the rafters. Distance between rafters: correct calculation

So, in order for the structure to serve for a long period of time, to be strong and also reliable, it is worth thinking not only about the foundation, but also about the roof. The building system of such an element plays a huge role., because it is the roof that takes on negative aspects from changes in weather conditions, as well as other situations.

The shed roof rafter system must be characterized by certain requirements, including:

Rigidity
Little weight
Quality material

Such requirements must be taken into account in order for the structure to serve for a long time.

The rigid characteristics of the element play an important role, because it is with the help of rigid elements that different parts are connected. Such elements should not undergo deformation processes. as well as spraying under no circumstances.

The basis of this design is a triangle, which is made using a special reliable frame. Each element of this frame is fixed to one another in parallel, and with the help of strong fixing, the stability of the entire structure is ensured.

Shed roof rafter system: diagram

But, if such frames are poorly attached, they will be movable, this will only lead to negative consequences... Such a roof can collapse not only from strong winds, but also by itself.

If we talk about weight, then this the roof should not be heavy... That is why this system is made, in most cases, from wood. In the event that the weight is large enough, it is necessary to make a supporting base of metal.

There are times when use coniferous trees, the humidity of which is at least 18 percent. Among the prerequisites for using trees, we note:

Antiseptic treatment
Use of flame retardants

Only in this case, the nodes, in the area of which the entire system is precisely fastened, will be distinguished by high strength and reliability.

The high quality of the materials used is one of the main rules... The tree must meet the following characteristics:

1-3 different grades are used... It is important to pay attention that there are as few cracks as well as knots. For one meter of material, 3 knots with a height of no more than 3 centimeters are allowed. Cracks are also allowed in a minimum amount, but not along the entire depth.
It is advisable to make elements of a bearing nature from parts whose thickness is at least 5 cm, and the area is from 40 m2.
Planks made from coniferous trees can only be used with a length of no more than 6.5 meters, and from deciduous trees - up to 4.5 m.
It is advisable to make pillows, purlins, and also a Mauerlat from trees that are hardwood... Such material should be pre-processed with the help of one or another high-quality antiseptic.

Shed roof structure

So, before starting the manufacture of the system, it is very important to know what are its main parts:

Mauerlat, which can be called the foundation of the system. With this part load is distributed evenly and correctly.
Run represents an element that is confident holds all the legs of the rafters... The ridge version is at the top, but the side elements are located on the sides.
The rafter leg is installed to determine the angle of inclination of the slope, as well as for the reliability of the entire roof, its appearance. It is this product that fixes the individual parts of the system.
The tightening helps the legs to stay in place, do not move apart. This piece connects them at the bottom.
Racks, as well as struts give additional leg stability.
Lathing represents boards, as well as trimmed beams. It is stuffed perpendicularly transfers the load to the rafter legs.
The overhang of the entire roof protects against precipitation.
Ridge is the place where two roof slopes meet. It is along this element that the crate is stuffed, due to which there is reinforcement of one or another part of the roof.
Filly are used when the length of the legs is short, as a result of which they create an overhang.

ATTENTION!

Only if you take into account the described parameters will you get a reliable roof.

A gable roof is characterized by the presence of one slope, which is characterized by an angle of inclination from 14 to 26 degrees. In the case when the roof is made for a small house, then the span will not exceed 5 cm, therefore it is recommended to make a layered version system.

The support of such a roof is made on external walls. as well as on a wall that exists inside the object. Rafter systems are used in truss rafter cases.

Roofing cake, or rather, its design, depends on what kind of final coverage option will be chosen. But, regardless of the material, this element maximizes the "life" of the roof, durability.

The single-slope type requires special attention, since it is this stage of construction that has the maximum effect on the climate that the structure will have.

The structure of the rafter system

Fastening the rafters of a pitched roof

The fastening scheme is quite simple, since it is a parallel laid out boards, which rest on two walls. To install the legs, special transitional elements are used, which are made of wood.

Depending on what material is used, the following can be used as a transition piece:

Mauerlat... In the above single slope roof system, there are two wooden beams that lie separately and complete the walls.
Upper part of the foot, which is made of beams.
Top strapping the whole frame.

Although the design of this roof is simple, there are some subtleties of fastening the rafters that are important to know about.

The fact is that the nodes that are applied must take into account all the negative aspects of a material such as wood.

When designing, one should take into account the solution of the following tasks:

The ability to easily move wood parts from one another
Adaptation to the consequences that may occur after the subsidence of each wall, in order to take a stable position
Elimination of all possible causes of a violation of this or that connection

The triangles are fastened according to the scheme: the horizontal side is installed on the Mauerlat, fixed. It is very important that it has enough space for docking. with other elements.

It is important to set the rafter legs at a certain angle to the supporting elements. It should be understood that two points are small enough for a strong attachment, so there are methods that are used to avoid negative consequences.

First of all, it is important to increase the total area of interaction of the rafters as well as a support part with:

Select cuttings
Saw down the upper and lower edges of the legs. With the help of such actions, you can easily create a support platform, increase stability.

Fastening the rafters

Rafter step

The distance between the rafters of a pitched roof is calculated depending on whether what material is chosen, as well as the section... Such calculations should be done at the stage, building codes and rules are used.

The calculation for the above roof option is very simple. There are no racks, as well as braces, as a result, only the rafters of a single-pitched roof are taken into account.

Usually, for such a roof, coniferous wood material is used, the moisture factor of which is approximately 20-22 percent. Such boards should be characterized by evenness, the absence of blue.

Each roofing material is characterized by its own characteristics, therefore, the step of the rafters is also different:

Using the distance depends on the size of the sheet... Usually, the spacing of the beams is at least 60 cm and up to 90 cm. With a larger distance, boards with a large section - 150 mm are additionally used. It is important to take into account the use of the lathing, the cross-section of which should be 30 * 100 mm, and the installation is carried out taking into account the span of at least 50 cm.
often used, but its weight is taken into account... The beams for such a system are pre-dried. When determining the step size, the length of the boards should be taken into account. At the maximum length, it is worth making the minimum distance between the rafters. The same rule is used with the minimum length of the beams - a large step distance. Usually, 80 cm is considered a safe step.
Under, which is used much more often than the two above materials, beams with a small section are used... The step in this case is equal to a number from 60 to 90 centimeters. The bar should be used with a cross section of about 50 * 150 mm.
Using you should understand that it is in the form of sheets... Beams should be placed with a distance that will not be less than 60 centimeters, but also not more than 90 centimeters. The section of the bar is 50 * 200, and you can also use 50 * 150 mm. When using a smaller section, negative aspects can be expected, since such a section will not be able to provide high strength to the legs.
Under which is used very rarely, rafter legs with a section of 50 * 100,50 * 150 are used. The step is not less than 60 centimeters, and also not more than 80. In this case, the step differs depending on the roof structure.

Rafter pitch table

Installation of the rafter system

When deciding to independently install the rafters of a pitched roof, you should first prepare all the elements, and also process them with special means.

Boards should be laid on both sides of a certain roof and laid in the grooves.

Only after this is it important to attach several extreme rafters.

CAREFULLY!

Consider that it is important to hammer in one or two nails per joint... The legs are set taking into account the previously stretched strings, after which they are similarly nailed. After that, the lathing is installed, and the roof is also laid.

After calculation, design, there are certain stages of installation:

Installation of the supporting beam... A large timber is laid along the wall of the object. Previously, it should be scolded, soaked with an antiseptic... It is important to lay roofing material along the end of the wall; mount the beam on it at the level with the help of anchor bolts.
Processing of timber, roofing elements... It is planned to leave the board above the eaves of the roof - a level of about 40 cm on each side, depending on. It is important to consider that the steeper the angle, the less it costs to fly.... When using metal tiles, as well as corrugated board, the step is 120 centimeters. In the case when the width is more than 6 meters, it is recommended to reduce the step to 1 meter. The board cuts into the Mauerlat for strength.In contact with
The roof frame must be reliable and durable. But without competently carried out calculations, this is difficult to achieve. In the process of carrying out the calculations, it is determined at what distance to put the rafters on the roof.

What can an incorrect or inaccurate calculation of the loads to which the rafter structure will undergo? To the most negative consequences, ranging from deformation of the rafter legs and damage to the roof covering and ending with the collapse of the base of the roof frame. Therefore, when designing buildings, the list of mandatory calculations contains data on what the distance between the roof rafters should be. There is a certain methodology that allows you to calculate this value.

Method for calculating the distance between the rafters

The distance between the rafters on the roof is called the rafter pitch. As a rule, the pitch of the rafter legs in the roof structure usually exceeds one meter, and the minimum gap ranges from 60 centimeters.

The calculation of the required number of rafters for a roof of a certain length and the pitch of the rafters is made as follows:

Roof structure for metal tiles

In the construction of suburban private real estate, metal roofing can be found most often. This roofing material is similar to clay tile decking, but has a number of advantages over it. Sheet metal shingles are easy to install, so the roof can be erected in a shorter time, the rafter system for metal shingles is also not difficult.

Metal tiles are lighter than ceramic products, the difference in weight sometimes reaches 35 kilograms per square meter, depending on the thickness of the products (read also: ""). Due to a significant reduction in the weight of the roofing, it becomes possible to reduce the thickness of the elements of the rafter structure and the dimensions of the cross-section of the sheathing bars, to increase the pitch of the rafters.

Under the metal roofing, the rafter legs are mounted with a distance of 600 to 950 millimeters, while the cross-section of the construction material is 150 by 50 millimeters. According to experts, in this case, if you place a 150 mm thick insulation between the rafters, then such thermal insulation will create comfortable conditions for staying in the attic room. At the same time, for greater reliability, it is advisable to choose a 200 mm insulation.

When installing the rafters, to ensure ventilation of the space that is filled with insulation, holes are drilled in the rafters near the upper roof with a diameter of 10-12 millimeters.

The technology of creating a rafter system for metal tiles does not differ significantly from structures for other types of roofing materials. The only feature is that for the rafters, the upper support is mounted on the ridge girder from above, and not on the side of the ridge beam. The presence of a free zone between the rafters ensures air circulation under the roof deck, and this, due to the use of metal material, reduces the risk of condensation.

Shed roof rafter system, main advantages and characteristics ").
The distance between the rafters of the gable roof is made taking into account the size of the heat insulator, which is laid between them. The approximate step between the rafter legs is 1-1.2 meters (read: ""). Rafters regulate the size of the roof overhang.

The roof structure is one of the main enclosing elements of the building, the quality characteristics of which are subject to rather stringent requirements.

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

From above, the elements are equipped with a polymer coating, which protects metal from aggressive external influences.

Externally, the metal tile is similar to ceramic, but it is more durable. This material is used for covering pitched roofs, the slope of which must be at least 14 degrees.

This is the national team roof frame structure 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 roofs are made, as well as the laying of the roofing finishing roofing layer.

Rafter system

The constituent elements of the rafter roof, and their main characteristics:
- Mauerlat. Softwood beams, which are 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 the load-bearing wall along its entire length. With the help of the Mauerlat, the loads from the roof are evenly distributed throughout the building.
- Sill. A bar with a square cross-section similar to a Mauerlat. It fits transversely to the 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 severity of external atmospheric influences (rain, wind, snow, hail, etc.).
- Rack. Vertical connecting elements that distribute the compressive loads from the ridge assembly over the entire area of the bearing walls. They are made of square beams, the length of the edge of which is determined by calculation.
- Tightening. It is the final horizontal element of the triangle of rafter legs, which does not allow them to creep under the pressure of external loads and the own weight of the roof. Used in hanging rafter systems.
- Braces. They perceive and redistribute bending loads from the ridge knot.
- Lathing. It consists of boards, bars or plywood sheets (in the case of subsequent installation of bituminous tiles), which are located at right angles to the rafter legs, being an additional stiffening element.
- . The junction of two roof slopes.
- Overhang. A roofing element protruding beyond the supporting wall structures at a distance of about 0.4 m. Its purpose is to limit the penetration of moisture to the walls.
- Filly. These elements are attached to the ends of the rafters if they are not long enough to organize the overhang.
Varieties of pitched roofs
Depending on the number of inclined planes, roofing structures can be divided into:

In private housing construction, the option is most often used gable roof since he has a number of advantages. These include:
1. Practicality. The 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 in the most optimal way.
2. Simplicity of the device and operation. The assembly and joining of two pitched elements is much easier than for complex roof structures. In addition, the repair of such a roof will also be easy.
3. Aesthetics. A gable roof structure blends seamlessly with 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 for a gable roof made of metal tiles has no significant differences from structures with other covering roofing materials.

But, due to the fact that metal thin sheets have a low specific weight, the rafters will experience less constant stress.

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

For roofing under metal tiles, the optimal the angle of inclination must be at least 14 degrees.

For roofs with two pitched elements, the following apply options for arranging the frame:

Roof rafters for metal tiles.

In this case, 2 supporting rafter legs are fastened together with the help of bed(horizontally) and racks(vertically). The bed is laid parallel to the Mauerlat element, while taking on part of the force. The rafter system under the metal tile is taken over 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, in this version, two rafter legs fastened together only in the ridge knot... In this case, significant expanding forces on the supporting elements arise, which limits the use of hanging rafters only for buildings with a span of no more than 6 m. In some cases, an additional connecting element is installed - a tightening that takes on part of the spacer loads.

They can be made of wood or metal, as well as installed at the bottom (act as a load-bearing beam) or at the top of a triangular structure. It is worth considering that the higher the puff is, the more efforts it will perceive.

NOTE!

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

Combined option

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

How to calculate the angle of inclination of the rafters?
To implement a gable roof, you need to know a few geometric values of the building, namely:
- Half span width - L;
- Distance from the load-bearing wall to the ridge of the roof (or the height of the support post) - H.
Standard formula: α = arctan (L / H)

Where α is the required angle of inclination of the roof.

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

l = H / sinα.

Where l is the length of the rafter.

The angle of inclination of the rafters

How to calculate the load?

To carry out the correct selection of parts of the roof frame, it is necessary calculate the values of temporary and permanent load acting on its structural elements.

The permanent load includes the weight of all elements, as well as the mass of the supporting elements themselves and the battens.

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).

Constant load calculation

Roof cake weight.

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

The weight of the rafter system.

It is determined by adding the weight values of the lathing, rough flooring, as well as the supporting 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 the length of the elements;

P - Density of the wood used (depends on the species).

Total permanent load = weight of the rafter system + weight of the roofing cake.

Calculation of temporary loading

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

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

Formula for calculation:

Wm = Wo × k × c,
Where Wm is the value of the wind load;

Wo is the normative value of wind pressure, determined from zoning maps;

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

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

Determined by the formula:

S = µ × So;
Where So is the normative value of the snow load, determined from the zoning map.

µ - coefficient, which 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 a bar and calculate the pitch of the rafters for metal tiles?

Determination of the value of the cross-section of the rafter beam is carried out in several stages.

Calculation of the load distributed on each running meter of the structure:

Qр = L × Q;

L - Step of rafters.

The L value is calculated as follows:

The length of the roof slope is divided by the intended step 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. At the last stage, the value of the axial distance between the rafters is determined by dividing the length of the roof slope by the number of rafters.

The distance between the rafters under the metal tile - the standard pitch is 0.6-0.95 m.

Rafter step

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

Where b is the width of the cross section,

r is the value of the normative resistance of wood to bending loads (determined according to the normative documentation, depending on the type of wood).

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

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

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

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

Installation of rafters for metal tiles
All installation work on the roofing is carried out at a sufficiently high height. To minimize the risk of falls and to make it much easier to work at heights, it is possible to assemble the frame of the supporting truss 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 manufactured in several stages:
- The planks are lifted over the walls of the building, aligned, and then held together with a nail.
- Align the angle of inclination of the boards in accordance with the project, by lowering and raising them. The elements are fixed.
- The result should be a structure that resembles 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 to each other. 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 the load-bearing walls in the longitudinal direction. Fastening is done with studs (on an armored belt or masonry) or with a wire rod (for buildings with a low roof height).

CAREFULLY!

When using a hairpin connection, the connecting elements no need to walled 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 run, which serves as a supporting part for the entire structure of a gable roof. It is made from a bar or hewn log. If the span of the building is not more than 6 m, its support can be carried out without additional supporting elements. Otherwise, construction trusses must be used for installation.

Mounting. Part 1

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

Rigid connection. It is carried out using corners and beams. Less commonly, fastening is used by means of a saw 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 wire structure.

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

It is necessary to carry out the installation of wooden trusses in a certain sequence. First, the extreme trusses are installed, located at the ends of the building. Then a cord or rope is pulled between them, with the help of which the verticality of their installation is checked. Further, under the cord, further installation of truss structures is carried out in accordance with a given design step.

Mounting. Part 2

The creation of a roof from a metal tile is a rather laborious process that requires certain skills and a well-stocked hand. Therefore, to carry out the correct installation, you must at least work under the supervision of a competent specialist.

Useful video

Video instruction for self-installation of rafter legs:

The construction of the roof of a building is an important stage in the construction of a house, while it is necessary to calculate the pitch of the rafters as accurately as possible, since the reliability and service life of the roof will depend on this.

If the master does not pay attention to the calculations and installs the rafters, focusing only on his own eye, then the frame will turn out to be either too heavy, moreover expensive, or fragile.

General calculation rules

The step of the rafters is the distance from one to the other rafter leg. It is believed that such a distance is set in the range from 60 cm to 100 - 120 cm (when determining the optimal width, one must take into account the dimensions of waterproofing materials and insulation).

The exact pitch of installing rafters for a gable roof can be calculated according to the following diagram:
- we measure the length of the slope along the eaves of the roof;
- we divide the measurement data by a certain step (we determined the step of 1 m - we divide by 1, if the step is 0.8 m - we divide by 0.8, etc.);
- add 1 to the resulting number;
- we round the total (upwards) - we see the number of rafters for installation on one slope of a gable roof;
- the length of the ramp is divided by the resulting number and we get the exact step between the rafters.
For example, the length of the roof slope is 30.5 meters, taking into account the width of the rolls of insulation and waterproofing, a step of 1 meter is chosen.

30.5 m / 1 m = 30.5 + 1 = 31.5. Rounding up gives a result of 32. 32 rafters are required per roof frame.

30.5 m / 32 pcs. = 0.95 cm - the value of the distance (step) between the centers of the rafters.

However, this formula does not take into account the nuances of certain roofing materials, therefore, in the future, the article will consider how to calculate the correct pitch of the rafters for the most popular coatings.
It is especially worth highlighting the rafter system when erecting a hip roof (envelope). The construction of such a roof begins to be built precisely from the hip legs, into which the rest of the rafters are then cut.

A hip that is over 6 m in length is often reinforced by stitching it in two pieces. Otherwise, the installation and calculation of the pitch of the rafters for a hip roof are similar to the installation and calculation of a gable roof.

System of rafters for ceramic and metal tiles

The use of metal tiles in the construction of houses in the private sector is the most common phenomenon, which is facilitated by a number of its positive qualities.

Firstly, it is the low weight of the coating, which facilitates installation and helps to reduce the load on the supporting structures.

Secondly, large roof areas can be quickly covered with sheets of metal tiles, which is very convenient, especially if you choose a gable roof option.

The pitch of the rafters under the metal tile is set in the range from 60 to 95 cm, since the relatively low weight of the roof does not require increased resistance. Due to the low weight of the coating, the thickness of the rafters can also be reduced.

As for the thickness of the thermal insulation material used to insulate metal roofs, experts believe that when installing an attic under it, for greater confidence in reliability, thermal insulation of 20 cm can be used, in other cases 15 cm is enough.

A feature of roofs covered with metal tiles is the possibility of condensation accumulation.

This can be avoided by organizing ventilation during the installation of the rafters: for this, at a short distance from the top in the rafters, you need to drill several holes (about 10 mm in diameter).

As for the installation of a rafter frame under a coating such as natural (ceramic) tiles, you must remember about its high weight.

In comparison with other modern materials, tiles are 10 times heavier or more. Given this feature, experts recommend using exclusively dry wood under it in order to avoid sagging after drying.

For rafters, in this case, you need to use a bar with a section of 50 - 60 mm * 150 - 180 mm; the width of the step of the rafter legs is set in the range of 80 - 130 cm, while the greater the degree of the roof slope, the greater the distance between the axes of the rafters.

The step of the rafters is also dependent on their length: the greatest length will require the smallest distance, and vice versa. Otherwise, the roof frame will lose the necessary stability.

Taking into account the size of the tiles (as a rule, its length does not exceed 40 cm), it is necessary to correctly calculate the width of the step of the sheathing stuffed on the rafters.

From the length of the slope, you need to subtract the length of the bottom row and the number of centimeters between the crate and the last bar.

Frame for ondulin, corrugated board and soft roof

Such types of roofs as corrugated board and ondulin are relatively new on the market of materials. At the same time, they are successfully used both in the construction of a gable and a hip roof.

The weight of these materials is practically equal to the weight of the metal tile, therefore, the calculation of the step width of the rafters will be similar to the calculation when laying metal sheets. The step of the rafters under the corrugated board is determined from the range of 60 - 90 cm, under the ondulin - 60 - 100 cm.

The sufficient thickness of the rafters themselves when covering the roof with ondulin and corrugated board is 50 * 200 mm.

If it is necessary to increase the distance between the centers of the rafters, then the strength of the transverse lathing can be increased.

The rule for installing the lathing under the corrugated board is similar to installing the lathing under the metal tile: the last board must be taken wider than the others (as a rule, 15 cm thicker).

The lathing for ondulin must be made continuous to increase the resistance of the material to various weather conditions.

Speaking about the device of the truss system for a soft roof, it is worth remembering the types of such material presented on the markets: this is a roll type of roof and bituminous shingles.

The name itself suggests that a very strong foundation is needed for a soft roof, which will allow it to withstand heavy snow cover, gusts of wind and torrential rains.

The main requirements for roof frames for soft roofs are that they must be strong and even.

The strength should be calculated for the thickness of the snow specific to the region in which the structure is being erected and the average weight of an adult male to allow for troubleshooting.

A flat roof should be for the reason that it excludes the possibility of sagging under the influence of the above-described weather phenomena.

Between the axes of the rafters for a roof frame with a soft roof, the step should be small, no more than 50 cm.

If the step is still larger, you will need to make a rough crate, on which the main one will be mounted, solid.

The counter lattice will help the soft roof not to bend and will increase its service life by an order of magnitude. For a solid lathing, a 30 mm board or an OSB 20 mm board is more often used.

If a soft roof is provided as a covering for a hip roof with the organization of an attic space, then it is necessary to think about its insulation, having thought over a filing for laying insulation, hydro and vapor barrier.

These are all the subtleties of the roof frame device for a soft roof.

Slate roof rafters

Despite the richness and variety of modern materials, the good old slate remains quite popular. The use of expensive roofing coatings is far from always justified, and this is when an asbestos-cement sheet comes to the rescue.

The weight of the slate is quite impressive, while its installation does not require any grandiose lathing. This is because such a roof itself is strong enough.

For the construction of the roof frame, in this case, rafters with a section of 150 * 40 mm and a bar with a section of 35 * 35 mm for the lathing are required.

Lumber for the construction of the frame should be stacked and kept for some time to give the same level of moisture.

After completing the drying process, it is necessary to determine the bend. The rafter legs are recommended to be installed with the concave part (tray) upwards - so the water, if it hits the rafters, will slide down, bypassing the attic space.

Before starting the installation, the beams are checked for knots in them and rejected, since the knotty material may not withstand the weight of the roof.

In this case, rafter fasteners are made with nails, the optimal length of which is 15 - 20 cm.

The nails should pierce the beam through, but the protruding ends should never be bent, since it is required to maintain the mobility of the structure.

When the wood dries out and deforms, this technique will prevent cracking of the slate sheets.

The lathing for the device of a slate roof can be solid or sparse. Solid is made from a sheet of OSB or plywood and is more often used when laying flat slate.

Sparse is typical for laying wave slate on it. For a sheet with a standard size of 1.75 m, the lathing step is about 80 cm. It makes no sense to make the lathing more frequent, since the slate has a sufficient margin of safety.

After analyzing the materials of the article, you can independently engage in the construction of the frame of a gable and hip roof, having determined for yourself their features and properties of roofing materials.

It will not be superfluous to remind that the calculation of the rafter step is a very responsible occupation, and it is necessary to approach it responsibly, as this will avoid mistakes and speed up the progress of work in the future.

The rafters are one of the individual elements of the supporting structure of the roof, with the help of which its slope is formed. In the design, the rafters are attached with their upper end to the ridge, and the lower end rests on the Mauerlat, with a straight slope, or on a rack (with a broken roof). Rafters are made from edged boards with a section of 150x60 mm or a bar of 150x100 mm. The distance between the rafters, at which they are from each other after installation, is called a step, which can be in the range of 600 - 1200 mm.

Roof systems, their types

Depending on the type of installation of the rafter legs, systems are divided into 3 types:

Why the step of installing the rafters may depend

The pitch of the rafters on the roof depends on such factors, how:

Taking into account all these indicators when calculating, you can get a strong and reliable rafter structure, which will be a high-quality support for the roof for a long time.

It is the calculation, subject to the foundations of standard loads, allows you to choose the right distance between the rafters. As a rule, the guideline values can be determined by the Sheaves, and the calculated values are derived on their basis separately for each structure.

In this case, it is taken as a template value to use rafter legs with a section of 150x50 mm with an optimal distance between rafters within 0.8 - 1.8 m / p. but it should be remembered that when the slope of the roof slope changes, the distance between the rafters also changes.

Calculation of the rafter structure

The strength and stability of the entire roof directly depends on the quality of the calculation for the selection of the cross-section of the rafter legs and the distance between them. Regardless of what type of coating will be chosen: profiled sheet, slate or metal tile, the initial calculation should remain unchanged. After all, each calculation is based on the structural strength under mechanical loads, and the rest of the effects are no longer important.

When calculating the choice of the optimal distance between the rafters for the roof, the following parameters are taken as a basis:
1. Roof covering type.
2. View of the rafter system and the design features of the roof.
3. Feasibility and economy.
For a small house, the calculation of the structure for the roof can be done by yourself. True, the method of calculating the elements for the roof truss system is rather difficult, and it is recommended to do it using programs specially created for this. Especially if you need to calculate a complex sloping roof with a large area, most likely, you will not be able to do without a specialist. In this case, the calculation of the step of the rafters will also be repelled by the standards - the minimum step is 0.6 m, the maximum is 1.2 m.

Calculation method

Produced in this way.

- The length of the building is measured along the cornice.

- The resulting length is divided by the estimated distance between the rafters. For example, the estimated pitch of the rafters will be 0.8 m / p. (The average distance is considered to be 950 mm).

- After performing this action, add one to the result obtained, and round the resulting amount. Thus, the required number of rafters is obtained on one side of the ramp. After that, the length of the building must be divided by the number of rafters obtained, and as a result, the exact axial pitch of the rafters is determined.

Example, - the length of the building is 26.5 m / p. the distance between the rafters is supposed to be 0.8 m. So:

- 26.5 m ˸ 0.8 m = 33.1 33.1 + 1 = 34.1. As a result, after rounding, it turns out that 34 rafters need to be installed on one slope.

26.5 m / n ˸ 34 Art. = 0.77 m - this value is the distance between the rafters along their central axes.

But this is only a general calculation method, which does not take into account the peculiarity of the planned roofing. Therefore, experts recommend calculating the step between the rafters for a certain roofing material and insulation, for example, for the most popular roofing metal tile today.

Roof structure for metal tiles

Metal tile visually imitates ceramic roof tiles. It is made from thin sheet steel by cold stamping. Thanks to the polymer coating, it has a high resistance to weathering and a rather attractive visual appearance, is not afraid of sudden temperature changes.

The advantage of metal tiles

Often used in the construction of most mansard roofs.

The section of rafters made of wood for a roof made of metal tiles is usually standard 150-50 mm, but the distance between them can be from 600 mm, but not exceed 900 mm (depending on their angle of inclination, which can range from 22 to 45 degrees). This limitation of the pitch of the rafters is due to the fact that the lathing for the metal tile is mounted with a distance from each other within 300 mm. The standard timber used for the lathing has a cross section of 30x50 mm or 50x50 mm. This means that each rafter is subject to additional stress.

Stability of the roof structure against various mechanical loads depends on four factors:

An important factor when calculating a rafter structure, is the estimated maximum load on the roof, the formation of which includes:
1. The weight of the entire rafter structure.
2. The weight of the lathing under the cover.
3. Insulation and roofing weight.
4. Snow load (determined by a special, unique for each region, reference book).
5. Wind load (also according to a special reference book for the region).
6. Weight of a person with a tool (repair work, estimated weight - 175 kg / m²).
When installing the rafter system, the distance of the rafter legs should not exceed an average value of 0.9 m / p. except for certain cases stipulated in advance.

If, when calculating the loads, any inaccuracy is made in the selection of material for the roof and the location of the rafters, it may occur its deformation and destruction of the roofing... A reliable roof structure will be guaranteed only with the correct calculation of the cross-section of the rafters and their installation pitch.

It should be remembered. There is no universal value for calculating rafter structures. When building each house, an individual calculation is required.

Shed roof rafters

Shed roofs can often be found on small outbuildings. They can also be used on private residential buildings, but quite rarely. In such cases, the angle of inclination of the roof is quite small, and with such an arrangement of the load-bearing floor beams, there is a very great pressure on them, especially in winter.

Therefore, for a pitched roof, load-bearing floor beams are installed from a bar of large cross-section from 60x150 to 100x220 mm, depending on the width of the span to be covered. In this case, the distance at which the rafters are stacked from each other should be within 400 - 800 mm, depending on the angle of inclination of the roof.

For a pitched roof no complex rafter construction required, they can be simply laid on the walls, without even using the Mauerlat. In regions where winters are rather snowy with a lot of snow, it is recommended to erect the roof slope at a maximum angle of 35 ⁰ and place the roof in the "wind". This reduces the windage and leads to its self-cleaning.

Gable roof

Represents a structure assembled from rafters connected together in the form of a triangle. The upper part, which rests on the ridge, and the lower part on the Mauerlat, located parallel to each other on opposite walls. In simple terms, this is a roof consisting of two opposite slopes, connected by a ridge.

Gable roof structure, depending on its area, is mounted from separate rigid elements that increase the strength of the roof. These include struts that support the rafters, ties that connect the rafters to each other, jibs, purlins, support beams, etc.

For a gable roof, often the rafters are mounted taking into account the insulation in increments of 0.9 - 1.2 m / p. In this case, the strength of the mounted structure will be the highest if the formed triangle is isosceles. In regions with strong winds, it is recommended to install rafters with a slope of about 20 ⁰, and in snowy areas, the optimal angle should be 45 ⁰.

Although the gable roof is considered a classic, it has several alternative "related" types.

Roof roof

For mansard roof, for the calculated parameter for determining the step between the rafters and their number, the load is taken in the range of 40-60 kg for each 1 m / p. rafters, and the maximum deflection from its length is 1/250. Usually, with a properly selected section, this distance along the centers of the rafters is, as for a gable roof, 0.6 - 1.2 m / p.

It should be noted that the average load on the attic is approximately 200 kg / m2. So, with the standard calculation of the cross-section of the rafters, it is recommended to add a small percentage of the safety factor.

Hip roof

Among all the rafter structures, it is considered one of the most difficult ... It's practically a hipped roof, while the rafters of the end slopes are attached with their upper ends to the corner bowstrings, and not to the ridge. Therefore, certain requirements may be imposed on this type of roof during construction. In this case, the rafters are installed similarly to a gable roof at a distance of 60 cm - 1.2 m / p.

Mansard rooms under such a roof are made in rare cases, since its slopes "eat up" some area of the attic, especially in height.