Techniques for lengthening rafters from boards 50x150. Board for rafters: selection of building materials, calculations of parameters, installation nuances

In this article I want to tell you how a simple pitched roof is built. Why did I call it simple? Just because her truss truss consists only of rafters. No racks, struts, braces, etc. there is no. This type of roof is most often used in the construction of small garages, sometimes baths, various outbuildings to the house, any outbuildings, etc.

In general, when you read about shed roofs in literature or the Internet, you usually see such a statement - supposedly they are the cheapest, easiest to build and reliable.

Regarding cheapness and simplicity, I absolutely agree, but about reliability, I’m ready to argue.

Of course, maybe I live in the wrong climate zone, but in my practice I have never seen a roof that has two or more slopes (for example, hip, tent, etc.) collapse on a private low-rise building. All the collapses that have ever occurred have been on shed roofs. The reason for them is almost always snow loads plus the weight of people who work on the roof (for example, throw off the same snow).

So why is this happening. I think everything is simple here. Often, developers do not take a very serious and deliberate approach to the construction of a pitched roof. Basically, one of three mistakes is made, or several at once:

An unacceptably small slope angle is made;

As rafters, boards with an unsuitable section are used;

Too much step is taken between the rafters.

How to avoid these mistakes, we will now understand using the example of building a shed roof over a garage.

Let's say we have a box of foam concrete blocks with a wall thickness of 30 cm. Its dimensions are shown in Fig. 1.

Picture 1

Having started laying blocks, we must already decide on the angle of inclination of the roof slope. What should be followed here?

I think many people know that for each roofing there is a minimum angle of inclination of the slope at which it can be used. These values ​​are presented in table 1., compiled on the basis of SNiP II-26-76 * (“Roofs” - updated version of 2010):

Table 1.

I am sure some of you who have already studied similar tables on the Internet will be a little embarrassed when you see such numbers. I want to tell them about a little confusion that has arisen on various construction sites due to the banal inattention of their authors. Often, when compiling such a plate, they take the numbers from the above-mentioned SNiP II-26-76 *, but do not notice that in this document the angles are indicated in percentages (%), and not in degrees, as we used to measure them from school. I will not now explain how to convert percentages to degrees. There is this information on the network (there are also formulas, there are also tablets). Basically, we don't need it.

Now another note. Each manufacturer of any roofing (whether it be metal or bituminous tiles, etc.) sets the minimum angle of inclination of the roof for its products. It is indicated in the installation instructions. For example, for different manufacturers of metal tiles, you can see the numbers at 14 °, and at 16 °, etc. Often these numbers are higher than those determined by SNiP and indicated in Table 1.

But that's not all. All the figures given above characterize the angle of inclination of the roof, at which this roofing will not overflow water between adjacent elements under certain weather conditions. And these conditions in our country are very, very diverse. So snow loads differ significantly in different climatic zones. And wind turbines in general may differ within the same locality, depending on the location of your building relative to others.

Snow loads affect the possible deflection of the truss system, which changes the geometry of the roofing. In addition, with a large amount of snow, the so-called “snow bag” often forms on the roof (see Fig. 2):

Figure 2

Strong winds can also force rainwater through the joints of the roofing elements.

At one time I looked through many different sources, but nowhere did I find a specific dependence of the minimum angle of inclination of the roofing on the climatic conditions in the region. As I understand it, no one brought it out. Everyone uses values ​​based on previous years of experience. I can say that for shed roofs, in central Russia, it is usually not recommended to make the slope angle less than 20 °. We will also build on this value.

So, let on our garage (Fig. 1) we decided to make the angle of inclination of the ramp equal to 20 °. We will cover with corrugated board. Now we need to decide how high the walls need to be laid out. In this case, we make a low wall with a height of 2.4 meters. This value is chosen in each case individually, depending on your personal preferences and the features of your building. The height of the opposite wall is determined by a simple formula:

H in \u003d H n + V × tg α,

where H in - the height of the high wall;

H n - the height of the low wall;

B - the width of the building (garage);

α is the angle of inclination of the slope.

In our case, H in \u003d 2.4 + 4.8 × tg 20 ° \u003d 4.2 m. (Slightly rounded up).

Now you can start laying the foot of the garage. Please note that the last row is not laid at the high wall. Why will become clear later.

STEP 1: We begin the construction of the roof with the installation of a Mauerlat. As a Mauerlat, we use a bar 100x150 mm (Fig. 3). It is placed flush with the interior walls. Notice how the sloping wall is laid out.

Figure 3

Also, instead of a beam, you can use two 50x150 mm boards sewn together with nails. I wrote about such an example in an article about installing a Mauerlat. It describes several ways to fix the Mauerlat on the wall. In addition to them, I want to show you one more, which we sometimes use when building a roof on gas and foam concrete walls, when the customer does not want to make an armored belt (Fig. 4):

Figure 4

A reinforced roofing corner 90x90 is used here. We fasten it to aerated concrete using two ʺGBʺ dowels with a diameter of 14 mm. They keep great. We put such corners on the Mauerlat after about 80-100 cm.

Please note that a roofing material must be placed under the Mauerlat so that there is no contact between wood and aerated concrete and metal. In all subsequent figures, the roofing material is simply not shown, but its presence is mandatory.

STEP 2: We begin the installation of rafters. To do this, first of all, we need to decide on their cross section and the step between them. In this we will again be helped by the program described in the article “Rafter system. Calculation of rafters and floor beamsʺ ().

I want to clarify again. I am not the author of this program. But I always use it, for lack of anything else (more or less understandable). I have full confidence in the strength of the roofs that we have already built. This confidence comes during the construction process, when you climb the rafters yourself and when you inspect the rafter system a few years after the construction of the house (I have such opportunities).

The program is certainly not perfect and sometimes you have to make some assumptions yourself. Therefore, do not judge strictly. The main thing is that all these assumptions work towards increasing the margin of safety of rafters and beams.

Let's go back to our garage. Let's take the Moscow region as an example. The sum of snow and wind loads will be 196 kg/m 2 . Where this figure comes from, I described in detail in the article (link above). I think it makes no sense to repeat. By the way, just here I make one assumption in the calculation. In the program, when entering the initial data, the value of only the snow load is requested (Fig. 5). There is no column for entering the wind load at all. Therefore, I simply add it to the snow one, although I know that it acts in the other direction (snow - from above, wind - from the side).

Figure 5

We entered the pitch of the rafters 0.5 meters. The calculation result (in the Sling.1 tab) is shown in Figure 6. Boards with a section of 50x200 mm were selected for the rafters. Of course, the step is small, but where to go. If we take it equal to 0.6 meters, then this section does not pass the calculation. Of course, you can take, for example, a bar 150x100 as a rafter, then the minimum step will change. Here you can already improvise. I am used to working with boards of either 50x150 or 50x200 mm.

Figure 6

By the way, in the figure, the distance between the supports (4.2 meters) is the internal width of our garage.

Having determined the cross section, we mark the cuts of the rafters. We take a board 50x200 mm of a suitable length and put it on the Mauerlat (see Fig. 7). It should hang from the walls with a margin (we got 53 cm), so that after the final trimming, the cornices will turn out to be 40-50 cm wide.

Figure 7

Now, using either a square or a tape measure with a small level, we mark the lower and upper cuts. In this case, we make the width of the cut equal to the width of the Mauerlat - 150 mm. The depth of the gash in this case will be 48 mm (see Fig. 8). Such exact values ​​are given to me by the program in which I draw a three-dimensional model of the roof (Google SketchUp). In real work, of course, there will not be such accuracy up to a millimeter, but it is not particularly needed there.

In other articles, when considering roofs with large slope angles, such cuts are made not based on the width of the mauerlat, but on the basis of the maximum allowable cut depth. It is usually 1/3 of the height of the rafter section. Now we have 1/3 of 200 mm - this is 66 mm. We fit into this value. And making the width washed down more than the width of the Mauerlat makes absolutely no sense.

Figure 8

So, we got a template according to which we make all subsequent rafters and install them (see Fig. 9):

Figure 9

The end rafters do not touch the sloping walls. You can see this in the figure above. The gap is about 5 cm.

STEP 3: We manufacture and install cornice fillies (see Fig. 10):

Figure 10

We make them from boards of the same section as the rafters. On an inclined wall, before installing the filly, we roll out the roofing material. It is not shown in the figure.

The sequence is like this. First, we put two extreme fillies and pull the lace between them (see Fig. 11):

Figure 11

Then, with a step of about 0.8-1 m, we install the rest (see Fig. 12).

Figure 12

It is enough to fix the filly with 2 nails (120 mm) hammered into the end through the rafters. The end caps can be fastened with roof angles directly to the sloping wall.

STEP 4: We install end (wind) boards (see Fig. 13):

Figure 13

We use inch boards 25x200 mm.

Also, we need to lay the Mauerlat on a high wall (see Fig. 14). This can be done either with aerated concrete or ordinary brick. Again, the tree must be separated from other material by a layer of roofing material.

Figure 14

STEP 5: We hem the cornices from below. This is done depending on the final finish of the roof. The cornices are either sewn up completely, or, as in our case, only belts are hemmed for subsequent siding trim (see Fig. 15):

Figure 15

It is enough to use boards 25x100 mm as belts.

STEP 6: Now we make a crate (see Fig. 16):

Figure 16

The required section of the boards of the crate can be determined in the program that is used to calculate the rafters and beams (see Fig. 5). In our example, boards with a section of 25x100 mm are taken, their pitch is 350 mm. In the figure we see the inscription - "The bearing capacity of the crate is provided".

As a base for the corrugated board with which we want to cover this roof, in order to save money, you can use unedged inch boards. But you need to take only the so-called "second board" (see Fig. 17):

Figure 17

The price of such material is almost 2 times lower than that of edged material. There is just one very important note. Before laying the boards on the roof, it is imperative to clean off the bark from them. Beetle larvae (bark beetle) often live under it, which first eat the bark, and then proceed to the wood itself. Getting rid of them afterwards is quite difficult. Some say it's not possible at all.

STEP 7: Well, the truss system is ready. Now we cover the roof with corrugated board and sheathe the cornices with siding (see Fig. 18):

Figure 18

Thus, we made a non-insulated shed roof. It is clear that this design is only suitable for cold rooms. If we are going to heat the room, then the roof will need to be insulated. Let's see what additional work needs to be done for this.

We do the first five steps in the same way as described above. Then we expose the plugs for laying the insulation (see Fig. 19). We make them from inches (board 25 mm thick).

Figure 19

Now we put the heater. From below, a vapor barrier film should be sewn to the rafters. It is not shown in the figure.

The truss structure is the fundamental element of a pitched roof. Incorrectly calculated distance between the rafters, incorrect calculation of the load on the erected system of beams, their incorrect installation, most likely, will lead to deformation and collapse. The stability of the truss system depends on:

1. from strength at the bottom, to the ridge at the top;
2. the validity of the drawing of the support for the rafters, taking into account the length of the span;
3. wood quality;
4. rafter steps.

Obviously, the main condition for the reliability of the roof structure is a correctly calculated distance between the rafters. You can figure out how to determine this value for a single-pitched, gable, hip roof.

What are span length calculations based on?

A competent design calculation, in which the pitch of all rafter legs is calculated according to the same principle for any type of roof, is based on the following indicators:

1. type of roofing material (metal tile, slate, etc.);
2. distance (span) between adjacent supports;
3. the angle at which the legs of the rafter are attached.

• rafter weight;
• insulation weight;
• roof weight;
• crate weight;
• snow;
• wind;

the weight of a person or people who will subsequently be engaged in the repair, maintenance of the roof itself and the objects located on it.

Snow and wind are different values ​​for each region, you need to look for these indicators in the reference information of a particular area, region.

How to calculate truss gaps

The exact distance between the rafter legs is calculated using complex mathematical formulas, resistance materials, but many craftsmen cope with this task in their own way. After the calculation of the maximum load is carried out, the following actions should be performed:

• measure the length of the roof;
• divide the result by the span of the roof frame or the approximate step for installing the rafters, (the step of the rafters is the distance from one to the other leg of the rafter system, usually a standard value, approximately selected, is taken into account);
• add one to the result, round the resulting value;

After that, the length of the roof slope should be divided by the obtained value (the number of trusses) - the required step of the rafters will be obtained.

Calculation example. The slope has a length of 27m, the selected step is 0.8m.

27:0,8=33,75
33,75+1= 34,75
round = 35, The number 35 means that you need to put 35 rafters.

We determine the distance between the rafters: 27: 35 \u003d 0.8. That is, the leg is set one from the other at a distance of 80 cm.

The generally accepted standard is a value equal to 1 meter, a step of eighty, seventy, ninety cm can also be optimal. Obviously, the calculation procedure cannot be called accurate, because the type of roofing material is not taken into account.

Intervals between rafters used for different types of roofing materials

When calculating the step of the rafters, it is necessary to take into account the characteristics and dimensions of the roofing material. The most popular types of roofing are:

• corrugated board;
• ceramic tiles;
• metal tile;
• ondulin;
• slate.

These types of roofing are used for the installation of roofs of residential buildings, baths, outbuildings. For each type of roof and roof shape, single-pitched, double-pitched or otherwise, a certain gap between the rafters is used.

Decking

Decking is a modern durable material made of galvanized sheet formed into a specific profile. The material is lightweight and durable. When using it, the calculation of the distance between adjacent rafters is 60-90 centimeters. A greater distance is possible only if there is a large cross-section board that fastens the rafters. The crate for corrugated board is made from a board of thirty, mounted 50 cm apart, if the roof angle is 15 °, the corrugated board is laid on the crate, laid without gaps.

The step of the rafters under the corrugated board does not depend on its brand. So, C44, the heaviest material, is attached to a crate with a span of 30 cm, but the pitch of the rafters does not change.

Ceramic tile

The calculation of the pitch of the rafters for ceramic tiles, a heavy, expensive material, is somewhat different from others. For a material whose weight is large, only dried strong beams with a section of 50x150, 60x180 cm are used. The optimal distances between the rafters taken as standards are from 80 to 120 cm. The choice of interval depends on the slope and type of roof. The calculation must be made taking into account the length of the rafter beam. For the longest rafter, a minimum step is required, and vice versa, the short length of the rafter allows you to use a step of maximum width.

metal tile

Metal tile can be safely called the leader among all roofing materials. It is used for complex, hip, gable, hipped, pitched roofs. Its installation is much simpler than ceramic tiles. Metal tiles can be put on the old roof, ceramic tiles, slate can be replaced using the old step. The metal tile is 10 times smaller, therefore, beams of a smaller section of 50x150 are used, the step between the rafters is from 60-90 cm, standard values. It is especially convenient to insulate such a roof by including the width of the roll or sheet insulation in the calculation.

Ondulin

This type of soft roof is becoming more and more popular, lightweight, easy to install, strong and durable. Ondulin sheets are overlapped on a 40x50 crate made of coniferous boards (60 cm step).

The pitch of the rafter legs is from 60 to 90 cm. Beams are needed with a section of 50x150 or 50x200.

Slate

Slate is widely used to cover farm buildings, baths, houses, garages. Therefore, what should be the distance between the rafters when using this roofing material, many people know. The use of this particular material created a system of rafter pitch 60-80, battens 50x50. The crate is made of bars 50x50 or the thirtieth board, depending on the slope. For a sloping pitched roof, a batten pitch of 45 cm is used, for a gable roof - 65 cm.

How do the steps of the rafters of gable and shed roofs differ?

Each type of roof has its own strength. The pitch of the rafter beams depends on what margin of safety should be laid during the installation of a particular type of roof.

Shed roof structures, which are typical for simple household buildings, are made of beams mounted on walls. The distance between the roof rafters directly depends on their length. It is also important to take into account the cross section of the timber used, based on the fact that the longer the gap, the greater the load.

The gable system, which includes gable, tent, hip and other structures, is always mounted with thermal insulation. The standard step for such roofs is 1-1.2 meters. In each case, the calculation is carried out taking into account, as already mentioned, the weight of the roofing material and other things, SNiP 2.01.85 is taken as the basis, which considers all types of loads and impacts. The step is calculated according to the usual scheme given above. Be sure to take into account the angle of inclination. An angle of 45° allows the use of all types of roofing. With the same roof slopes, the pitch of one side is calculated.

Stick to the following tips:

• If a decision is made to independently arrange the roof, check the correctness of your calculations with specialists or, at worst, use the services of online calculators of construction companies.
• When determining the pitch of the rafters, remember about thermal insulation, any rolled or sheet insulation shrinks over time. Remember about ventilation holes, waterproofing.
• If the slope of the roof is 45° or more, the weight of the person is subtracted from the sum of the maximum load, which allows the use of fewer rafters (by 20%).
• Decide which type: layered or required for the selected roof geometry.
• Take your time with the choice of timber, it must be dry (residual moisture not more than 20%), made of coniferous wood.

The quality and durability of the roof largely depend on the correct calculation of the pitch of the rafters. It affects the laying of insulation, the fastening of roofing material and the installation of additional parts. Pay attention only to the requirements for the distance under the roofing sheets, then there may be problems with the insulation boards. And vice versa, adjusting the size of the insulation can make the frame too weak, and in winter there will be a threat of collapse. How to correctly calculate the distance between the roof rafters? We will talk about this in our article.

As a rule, the pitch between the rafters depends on several factors. But usually the distance fluctuates between 0.6 and 1.2 meters. These figures are rounded, in practice the distance may differ by several centimeters downwards. For an accurate determination, the following calculations must be performed:

1. Determine the length of the slope by measuring along the eaves of the house. Suppose that it turned out 17.8 meters.
2. Divide the figure obtained by the planned step of the rafters. If it was decided that the distance between the beams would be 0.8 meters, then 17.8 / 0.8 = 22.25.
3. Further, we round the result up and add one: 23 + 1 = 24. At this stage, the number of rafters required is determined.
4. Now we calculate the distance between the axes of the beams. To do this, the length of the slope must be divided by the number of rafters: 17.8 / 24 \u003d 0.74 m.

So, you will determine the actual distance at which the rafters for a roof made of metal or some other material should stand.

Often, when planning a roof frame, specialized calculators are used. They enter basic data and get the finished result. Nevertheless, you should not completely trust the program, since only a person can take into account some conditions. When calculating, you can understand how the system works, what loads are acting. If necessary, adjustments are made to strengthen or facilitate the design. Self-calculation will help to more accurately determine the required pitch of the rafters of a gable and single-pitched roof.

Step calculation depending on the roofing material

For each coating, its own standards and dimensions are developed for the truss system. The main factors are the strength of the material, its weight and resistance to external loads. Consider the main types of coatings.

Decking

The step of the rafters under the corrugated board can vary from 0.6 to 0.9 m. The final result depends on additional conditions, which we will discuss below. If for some reason the step should be larger, a transverse board with a large section is added. In this case, usually the rafters themselves are chosen with dimensions of 50x100 or 50x150 mm.

In addition to the rafters, a crate of 30x100 millimeters is used. The gap between the boards should be about 0.5 meters. It can be more, it all depends on the type of corrugated board and the height of the wave. Sheathing boards protruding beyond the boundaries of the eaves should have a thickness of 1.5 cm more than usual. This is done based on the need to mount ventilation, a chimney or a drain.

Ceramic tiles

The main difficulty in designing a roof frame for ceramic tiles is the large weight of the material for the roof. It is 10 times heavier than corrugated board and accounts for 40 to 60 kg per square meter.

Under such a coating, dry beams are used, with a moisture content of only 15%. Their cross section should be either 50x150 or 60x180 mm. With such indicators, the maximum allowable distance between the rafters can be 1.3 meters. The minimum allowable step through which rafters can be placed is 0.8 m. The roof slope affects the final decision: at 15 °, the step is 0.8 m, at 75 ° - 1.3 m.

The length of the rafter leg is also taken into account, the shorter it is, the larger the gap, and vice versa. In addition, if the slope is less than 45 °, and movement is planned on the surface, the beams are placed in increments of no more than 0.85 m.

The distance between the boards of the crate is selected so that each intersection of the tiles has its own base. The standard length of the material is 400 mm, and the amount of overlap during installation varies between 55 and 90 mm. It turns out that the distance between the central axes of the crate can be either 310 or 345 millimeters.

metal tile

In recent years, the question has been particularly acute: how to determine the distance between the rafters under the metal tile? It imitates more expensive ceramic material, but at the same time it has the positive properties of corrugated board. Installation of such a coating is simple and does not require large financial costs. All this makes the material attractive for the roofs of private houses.

The mass of metal tiles is less than ceramic, so a simpler frame is required. The section of the beams is reduced to 50x150 mm and the step between the crate is increased. The step of the rafters under the metal tile varies between 0.6 and 0.95 m.

Ondulin

The allowable step for covering from ondulin is 0.6-0.9 meters. The standard section of the rafters is 50x200 millimeters. Such dimensions will allow to withstand the load of the roofing pie on the gable roof.

On top of the counter-lattice, a crate of bars measuring 40x50 millimeters is attached. The pitch between the central axis is 600 mm.

Additional factors

When calculating the pitch of the rafters, attention is paid not only to the type of roofing. Many other points are taken into account, data on which can be found in reference books and SNiPs. Here are some of the factors:

1. Snow and wind loads. The more snow falls in winter and the stronger the winds blow, the smaller the distance between the beams should be. But, if you increase the angle of the roof slope over 45 °, then it is allowed to increase the step.
2. Choice of heater. To reduce the cost of insulation boards, it is recommended to take into account their standard sizes. They produce mats with a width of 600, 800 and 1200 mm. If this condition is neglected, then a large number of undercuts will appear, cold bridges and construction will be delayed.
3. lumber quality. It takes into account the type of wood, grade and section. As mentioned above, strength is affected by how well the beam was dried. When buying wood, pay attention to evenness and the presence of defects in the form of knots and traces of pests.
4. Floor beams and puffs. If you equip the attic floor under a gable roof, then the maximum distance between the rafters should be 0.75 meters.

The calculation of the distance between the beams for a gable and single-pitched roof is different. Even if he makes several slopes, for each it is necessary to make a calculation individually. This is especially true for buildings with different lengths of cornices.

Taking into account all these factors, it is possible to determine how far the rafters should be installed. Although all calculations can be done independently, since reference data is freely available, it is better to turn to professionals. They have experience in designing, they will quickly determine the required distance between the rafters. So, you will avoid possible mistakes and be sure of safety.

In building your dream home, are you already at the finish line, and it's time to deal with the intricacies of the truss system? Let's just say: pleasant worries await you: calculating the angle, weight and safety factor of rafters, an agreement with a familiar craftsman or company, or preparing all the necessary tools for independent carpentry work.

And so that tomorrow all these worries do not become a headache and you do not worry about whether this or that knot is done correctly, we have prepared this article for you. So, let's figure out how to make high-quality rafters for a gable roof with your own hands so that it is no worse than purchased ones.

• Short production time.
• Technological precision of all details.
• The same, already fitted dimensions of all structural elements.

But then be prepared for such cons:

• High cost (at least twice as high as if you planed the rafters yourself).
• Delay in delivery (especially in season).
• The use of low-quality or under-dried wood (and then the roof will “lead”).

So convenience or quality? If this is not the first time for you to cut or plan something out of wood, feel free to take on the manufacture of rafters! Here's what it all looks like in real life:

Rafters in the building world in a simple language are usually divided and the main ones, i.e. carriers, on which the roof rests, and on auxiliary ones, which are located inside the roof and serve as a support for hemming the ceiling and walls of the attic (if one is planned). The strength and reliability of the future roof depends on how accurately and correctly you calculate the truss system in advance.

The truss system of any gable roof itself consists of the following basic elements that you need to make:

• Mauerlat.
• Vertical racks.
• Crossbars.
• Rafter legs.
• Struts.
• Skate ride.

Complex roof structures with multiple elements are best left to a professional, but you can handle a small roof of a private house. To do this, you will need these simple formulas that will help you find out how thick the rafters should be, with what slope and what span:

How to draft a future roof?

The golden rule applies in the construction of roofs - measure seven times, and cut off only once. And first of all, it is important for you to understand that each rafter leg has its own individual location. Therefore, first, be sure to draw up a detailed project, and preferably in a special program. Only after that, according to your 3D model of the future roof, mark exactly where and what exactly the connections of the rafters with the Mauerlat and among themselves will be.

It is important to determine the angle of inclination of the rafters as accurately as possible and at what angle they need to make cuts. And don’t worry about how to make all these rafters for a gable roof yourself: you just need a regular machine.

Determine the angle of the roof: calculate the load

The angle of inclination of a gable roof is made from 5 ° to 90 °. But the most proven and standard option is 35 ° -40 °, where loads are most rationally distributed and building materials are consumed.

Straight slopes are built when only a non-residential attic will be under the roof in the future, the main function of which is ventilation and heat exchange regulation. But when the under-roof space is planned to be residential, attic, they initially plan the so-called broken gable roof. Its difference is that the slopes in the middle have, as it were, a kink that changes their angle to a steeper one. And for arranging the attic, and for protecting the whole house from the weather, this design is quite suitable.

Please note that most roofing materials are suitable only for slopes greater than 45°.

Fixed and variable roof loads

From the same loads depends on what step the rafters need to do for your gable roof. This table will help you choose the desired section of the rafter legs:

Indicators of rafters for deflection

Even strong-looking rafters may not be suitable for building the roof of a residential building due to the fact that they do not have enough deflection indicators. There are separate items in the section of SNiPs, which are called "Loads and Impacts".

And the easiest way to increase the strength of the rafters for deflection is to make the section larger. A little more difficult - to strengthen it with a beam, bringing its edge to the strut.

Reinforcing elements for rafters

The more racks, struts and fights - the more stability and stability the entire truss system has.

If you have a suspicion or even an accurate estimate that a simple roof structure will not withstand future loads, make additional reinforcement elements for it. Such prevention will never hurt, but it will save you from many problems. Note that it is especially disappointing when the roof of the garage falls through - right on the car. And for a residential building, such problems are not a joy.

Strengthen the rigidity of the truss structure struts, additional runs and support posts. Struts are designed to reduce the span of the rafter legs. The angle of their inclination to the horizontal is usually at least 45°.

A run is a horizontal beam, which is parallel to the ridge and is fixed on vertical posts. More on video:

Determine the type of roof: cold or warm?

And now about the concept of the attic. If you are building the roof of a bathhouse or a small master's room, it can be done using the most simplified technology - they put rafters, connected them in a ridge and covered them with sheets of roofing material. But for the roof of a residential building, where ventilation is important, this principle is indispensable. There will already be at least three levels:

1. The upper or first level of the rafters is about 200 mm.
2. The average is always equal to the height of the auxiliary rafters.
3. The third is already on the edge of the wall.

It is so convenient to lay insulation, because the roof of a residential building is distinguished by the fact that heat rises up and, in the absence of thermal insulation, the roofing is constantly heated.

Bottom line: in winter, the snow melts and slides down, freezing and accumulating even more near the cold eaves. There are many problems from this: long dangerous icicles, and a clogged drainage system, and the gradual destruction of the entire roof. Decide for yourself!

We determine the type of truss system: layered or hanging?

So, now is the time to think over the supporting bases for future rafters, which also need to be prepared in advance and on which many parameters of the roof itself will depend. So, the rafters are divided into layered, hanging and hybrid.

Hanging rafters are usually the lot of small and light roofs, the distance between the supports of which does not exceed 6 meters. But in buildings with a load-bearing middle wall or additional supports for the roof fortress, layered rafters are arranged. Or a combination like this:

Another difference is that the hanging truss system makes the Mauerlat work in compression, and the layered one in shear. But the main task of both layered and hanging rafters is to transfer the loads of the entire roof to the walls and foundation as evenly as possible.

We select material for rafters

So, if you have decided on future loads, it's time to choose the right material. As it is usually used for the manufacture of rafters:

• Wood. Solid wood, boards or glued beams.
• Lightweight metal profile. These are galvanized steel profiles.
• Black metal. These are I-beams and steel channels.
• Heavy reinforced concrete structures for industrial construction.

Dry board: an economical option

If heavy loads are not expected on the rafter system, then make the rafters from a dry planed board with a small section. But if knee-deep snow is not uncommon in your area and the roofing material will not be easy, then you will have to make some of the constituent elements glued. That's the whole difference.

It is most convenient to make elongated side rafters and diagonal rafter legs from the board. So, a board 40 mm thick, which is often used for outbuildings, is not suitable for a roof. Not less than 50 mm! Moreover, the longer the rafter leg is planned, the wider the board itself should be. So, rafters 6 meters long will have to be made from a board 150 mm wide, and even longer - from a board 180 mm.

For the roof of a frame house, this is really one of the best options!

And also the rafters from the board are the most economical, and at the same time they are almost not inferior in strength to the timber ones. It is only important to choose the right section and use high-quality material. Therefore, when buying material, be sure to take a special device for measuring wood moisture and use it. There is nothing worse than damp rafters. And it's not just about future mold: such a roof will lead and warp, because this material changes its shape when it dries. At the rafters, fasteners will fly and even the cover of your gable roof will bounce in places. In short, no problems!

But from an ordinary board it is most convenient to splice the rafters along the length:

Durable metal: resistance to dampness

And, you will be interested to know that rafters can be made not only from wood! So, iron truss systems, which were once used exclusively for industrial construction, are returning to their former popularity today. And, note, this material for the roof has many advantages, the most valuable of which is the complete absence of fungus from dampness. The under-roof space, after all, most often “pleases” with accidental leaks.

And the work itself with such rafters during installation is no more difficult than with wooden ones - see for yourself:

Beams: the benefits of quality wood

The beam is more durable, but it is bad because it has a lot of weight and cuts have to be made at the attachment points. For a log, this is not only a problem, but also some loss in the bearing capacity of such a rafter leg. But so far this material is the most popular for the manufacture of rafters.

Most of all, lumber is suitable for the manufacture of rafters, which meets the requirements of GOST 8486-86 or 2695-83. And this:

• Humidity is not more than 18%, measured with a moisture meter.
• Cracks that are not through and do not exceed half the length of the board.
• For each linear meter - no more than three knots, and each of them - no more than 30 mm in diameter.

Therefore, when buying wood for rafters, be sure to check the documents from the seller that speak of product quality.

The type of wood is also important. The fewer knots and cracks on the beams, the better. Some varieties also please with good moisture resistance and resistance to decay and pests. For the roof, this is what you need. Therefore, we recommend making rafters from coniferous wood, which is rich in resin, and resin is a natural barrier against decay. But special processing is still needed.

And take into account also this fact: in the manufacture of the rafter system, the material needs to be purchased 5-7% more than necessary, because it will not always be possible to make an ideal cut of the rafter or cut of the required depth. There will still be an overrun, and therefore stock up on it in advance so that you have a tree of the same moisture content and properties for the entire rafter system.

Otherwise, if you had to purchase some individual roof elements separately, they may take longer to dry (wood always dries), or vice versa. Distortions can turn out to be considerable, i.e. the entire roof frame will be constantly affected by various physical tensile and pressure forces. Any experienced roofer will tell you how bad it is and what it is fraught with. And therefore - take more material for the manufacture of rafters than you plan. If everything goes smoothly, there will be plenty to make the first bench in front of the new house.

Treatment with antiseptics and propylene

And at this stage it is already important to protect the future truss system from biological destruction. You do not want the roof to collapse after a couple of years of operation, do you? Therefore, be sure to treat the wood for the rafters with fire and bioprotection.

The rafters are usually impregnated with an antiseptic, and treated with a flame retardant on top. It is also possible to alternate such processing several times. If you use universal impregnation, be aware that it usually includes products with different service lives. For example, fire protection will end earlier than bio.

But the choice of means for processing today is huge. These are universal protective equipment, and a variety of flame retardants, and antiseptics. It is easy to decide: if you are building in a fairly hot and dry area, first of all use fire-retardant impregnations that deprive the wood of natural flammability. And if your house will stand where the humidity is high almost all year round, protect it from rotting.

You can, of course, use both drugs - but only without mixing, otherwise the whole material will deteriorate. You just need to choose one agent as an impregnation, and the second as a protective surface layer. Just try to dilute everything in the concentration indicated by the manufacturer. But do not treat frozen or damp wood with anything: its fibers simply will not absorb anything.

Video hint on the topic of rafter processing:

Note that a brush or a spray when processing rafters give little result - complete immersion and subsequent drying are much better. Just use a regular container, cover it with a film from the inside and make a “bathroom” for future rafters. Moreover, it is desirable to turn all this on the ground, as soon as you bring the material to the place, because. in the finished rafter system it will be difficult to get to the internal elements of the joints. And they are the most defenseless in terms of moisture. Dry after processing the part so that all sides are ventilated, and for at least 24 hours.

Do not forget also that wood, like any natural material, is subject to biological destruction. Therefore, in addition to fire-bio-protection, it is important to consider waterproofing in all places where the truss system adjoins the brick walls of the house, if any.

We make the right cuts on the rafters

Now let's move on to practice. First of all, you definitely need to make a convenient template, according to which you will make even, identical rafters:

And follow these instructions:

You will have to tinker with a rigid mount:

If we are talking about moving nodes, then follow this principle:

In practice, everything is really simple:

As you can see, the eyes are afraid, but the hands are doing!

How to assemble a truss system?

Finally, the rafters are ready, and you can proceed with their installation.

Build on the ground or on the roof?

So, in fact, everything is quite simple and somewhat similar to a children's designer. The easiest and most convenient way is to make farms right on the ground, and only then raise them. It is a little more difficult to assemble the rafters directly on the roof, but it is easier to lift them there. So start from this: if you have the opportunity (a crane, for example) to drag 200 kg of one truss onto the roof, drag it, if not, lift each individual rafter by 50 kg using improvised means and do the assembly on the spot.

So, first of all, for convenience, make a template according to which you will assemble the trusses, and another template for mounting cuts on the rafters (use plywood). You just have to cut the mounting cuts on the rafters, attaching a template, and connect them together at a certain angle. This triangle is called the truss truss.

Attention to strength - rules for increasing the length

If the thickness or length of the board is not enough to make a normal rafter leg, build up the rafters. And there are several ways:

1. Bring the boards together, folding them with wide sides and stitching them with nails.
2. Lay the boards in half the length, resulting in a particularly strong rafter leg that can withstand considerable loads.
3. By making an oblique cut at the ends to create a vertical anti-slip stop, and connect with a bolt.
4. Lay two boards with an overlap of a meter in length, connecting the rafters with studs or nails.

Also consider when calculating that the roof ridge accounts for about 50% of the load from the entire truss system. Therefore, always make the beam for the ridge so that it has a safety margin of at least 25% more than it was originally calculated.

And the most vulnerable parts of the truss structures are the lower ones, those that rely on the Mauerlat.

Cooking truss trusses

You need to fix the rafter knots with the help of:

• External straight brace.
• Metal corner plate.
• Internal metal rod.

You can also connect such rafters with studs - it will even be stronger. To do this, instead of a cut, we now make a cut in half a tree and connect the rafters with a ledge. Next, we drill a hole for the stud 12-14 mm and fix it with nuts with wide washers.

Let's start with an overview of proven grandfather methods:

Here's how they work:

When assembling a hanging type truss truss, you need to connect the upper ends of the rafter legs. To do this, cut the end of each at exactly the same angle at which you make the roof, connect the beams with cut planes and fix with two nails. Close the joint with a wooden lining or a metal plate.

Another useful tutorial:

Lifting and installation of finished trusses

Already on the roof, first of all, you need to start by installing those rafters that form the two extreme gable roof trusses (they are also called gable). To further secure them, put temporary struts. Next, stretch a strong cord between the extreme tops of the trusses, which will become the level for the intermediate rafters.

Now we raise and place all the other roof trusses at a distance of at least 0.6 meters from each other. Again, if some of the structures turned out to be quite bulky, prop them up with the same temporary supports.

The rest is a matter of technique:

The reliability of the roof and its service life mainly depend on how correctly the calculations are made.

One of the most important parameters of the rafter system is how far apart the rafters are located.

After all, the distribution of the load on the frame depends precisely on this desired parameter.

If the calculation is made incorrectly, then deformation may occur and the roof will collapse.

Therefore, it is extremely important to perform an accurate calculation of the interval between when drawing up a roof project.

Basic provisions of the calculation

The pitch of the rafters is the distance from one rafter leg to the other.

In the construction of roofs of private houses, this value is 1 meter.

But this figure is approximate.

To get the exact size of the interval, it is necessary to calculate the bearing capacity of the truss system of the selected type.

To perform the correct calculation, the following scheme should be used:

• first you need to determine the length of the roof slope;
• now the resulting figure should be divided by the value of the approximately selected rafter pitch. If you previously chose its value of 1 meter, then you need to divide by 1.

  If 0.8 was chosen, then it should be divided by 0.8, etc.;

• after that, one is added to the result obtained and the resulting value is rounded up. This action is necessary in order to get the exact number of rafters that will need to be installed on one slope;
• the total length of the slope must be divided by the number of rafter legs obtained in the previous calculation. And we get the exact distance between them.

To better understand everything, let's look at an example.

By measuring the length of the roof slope, we got 27.5 meters.

We choose a step of 1 meter to make it more convenient to count.

Further calculations will look like this:

Now we add the unit 27.5 m + 1 = 28.5 m.

We round up to the nearest value and get the number 29.

That is, 29 rafter legs must be installed on one slope of our roof.

Now we divide the length of the roof by their number: 27.5 / 29 \u003d 0.95 m.

So, in our case, the step of the rafter legs should be 0.95 meters.

This is a general calculation.

In which the peculiarity of a particular roofing material is not taken into account.

And he can significantly change this parameter.

When you know what kind of material you will use on the roof, some changes will have to be made to the calculation procedure.

Optimal and minimum value

The step is the unit of account.

After all, it depends, first of all, on the load on the roof frame and the section of the rafter legs.

You can take a thick board for their construction and make the interval between them 120 cm.

At this distance, the crate may begin to sag.

Yes, and how to lay the heater?

Indeed, for most materials, the width is 1 meter.

So they take an approximate step of 1 meter when calculating.

The minimum distance between is 70 cm.

And to obtain the optimal value for each material, it is necessary to perform a calculation.

Determining the pitch for a pitched roof

Shed roofing is the simplest.

Indeed, in the truss farm of such a roof there are only rafter legs.

There are no struts, racks, braces in its design.

Such a roof is usually arranged on garages, outbuildings, baths.

In order to determine the pitch of the rafters on a pitched roof, you can use the table:

As can be seen from the table, the rafter step depends on their length and cross section.

Distance between rafters for a gable roof

A gable roof is much more common than a shed roof.

And to explain such popularity is simple: the design is very simple, but for all its simplicity, the gable roof is distinguished by its reliability.

Its design is easy to adjust to any climatic conditions and any roofing material.

When calculating the pitch of the rafters of a gable roof, everything is performed according to the general calculation system (see above).

If the slopes have the same length, then it is enough to perform calculations for one slope.

If the slopes are of different lengths, then the calculation is performed for each slope.

It should be remembered that the limit values ​​\u200b\u200bof 70 and 120 cm.

What is the step depending on the material of the roof

Ondulin

If ondulin is used as a roofing material, then the rafter system is constructed from pine boards with a section of 50 x 200 mm, and the rafters should be located at a distance of at least 60 cm and not more than 90 cm from each other.

A crate of timber with a section of 40 x 50 mm is laid on top.

metal tile

Roofing from metal tiles is most often used in the construction of country houses.

Because this material is much lighter than ceramic or cement tiles.

Although in appearance it is very similar to her.

A small one makes it possible to use boards of a smaller section when creating a truss system, and use thinner bars for the crate.

Reducing the size of the elements of the rafter leg system, in turn, reduces the load on the walls of the building and its foundation.

During the construction of the rafter system under the metal tile, the rafters are mounted in increments of 60 - 95 cm.

The cross section of the material is 50 x 150 mm.

According to experts, if a heater having a thickness of 150 mm is placed between the rafters, then the most comfortable living conditions will be created in the attic.

To ensure ventilation of the space where the insulation is laid, when installing the rafter system, holes will be drilled near the upper roof with a diameter of 12 mm.

The technology for manufacturing a truss system for metal tiles does not differ significantly from the technology for manufacturing a frame for other roofing materials.

Its only difference is the installation at the top.

The upper support is mounted not on the side of the ridge beam, but on the ridge run.

The presence of a free zone between the rafters allows the air to fully circulate under the flooring, which helps to protect against the formation of condensate.

Ceramic tiles

The design of the system for ceramic tiles has its own characteristics.

After all, clay is used to make such a roofing material.

And this is very heavy material.

If we compare metal and ceramic tiles, the latter weighs 10 times more.

Accordingly, the truss system is significantly different.

On 1 square meter of the roof surface there is a load of 40 - 60 kg, depending on the manufacturer and brand of the product.

The rafters for such a frame system are made from wood that has been dried for a long time.

Such wood should have a moisture content of no more than 15%.

A beam with a section of 50 x 150 or 60 x 180 mm is used.

So more reliable.

And the distance between can be 80 - 130 cm.

The exact value can be called if the angle of inclination of the slopes is known.

If the angle of inclination is 15 degrees, then the pitch of the rafters will be 80 cm.

And if the angle of inclination, for example, is 75 degrees, then the step can be larger - 130 cm.

More than 130 cm interval between the rafters do not.

Also, when calculating the pitch of the rafters, their length is taken into account.

The larger the dyne, the smaller the distance between them.

The shorter the rafter legs, the greater the distance can be.

If the angle of inclination is 45 degrees, then the roofer can safely move along the roof if the pitch of the rafters is 80 cm.

Decking

When creating a rafter system for corrugated board, the minimum distance between is 60 cm.

The maximum value is 90 cm.

If for some reason the pitch of the rafters was more than 90 cm, then it becomes necessary to install transverse boards of large cross section.

The rafter legs themselves can have a section of 50 x 100 or 50 x 150 mm.

Slate

Despite the emergence of a large number of new roofing materials, asbestos-cement slate remains one of the most popular.

If it is planned to lay slate on the roof, then the rafters should have a section of 50 x 100 or 50 x 150 mm.

The distance between them is made not less than 60 and not more than 80 cm.

The crate is made from a bar having a section of 50 x 50 mm or a board with a section of 25 x 100 mm.

When constructing any building structure, it should be remembered that there are still unforeseen situations.

And, therefore, at and distances between them, it is necessary to provide a margin of safety.

Video about the installation of the truss system.