Rafters serve as the basis for the entire roofing structure, and their installation is one of the most important tasks when building a house. The frame of the future roof can be made and installed independently, observing the technological features of roofs of different configurations. We will present the basic rules for the development, calculation and selection of a rafter system, and also describe the step-by-step process of installing the “skeleton” of the roof.

Rafter system: rules for calculation and development

The rafter system is a load-bearing structure capable of resisting gusts of wind, taking on all external loads and evenly distributing them to the internal supports of the house.

When calculating the truss structure, the following factors are taken into account:

1. Roof angle:
   • 2.5-10% - flat roof;
   • more than 10% - pitched roof.
2. Roof loads:
   • constant - the total weight of all elements of the “roofing pie”;
   • temporary - wind pressure, the weight of snow, the weight of people who carry out repair work on the roof;
   • force majeure, for example, seismic.

The amount of snow loads is calculated based on the climate characteristics of the region using the formula: S=Sg*m, Where Sg- weight of snow per 1 m2, m-calculation coefficient (depending on the slope of the roof). The determination of wind load is based on the following indicators: type of terrain, regional wind load standards, building height.

Coefficients, necessary standards and calculation formulas are contained in engineering and construction reference books

When developing a rafter system, it is necessary to calculate the parameters of all components of the structure.

Elements of the truss structure

The rafter system includes many components that perform a specific function:

Materials for making rafters

Rafters are most often made from coniferous trees (spruce, larch or pine). For roofing, well-dried wood with a humidity level of up to 25% is used.

A wooden structure has one significant drawback - over time, the rafters can become deformed, so metal elements are added to the supporting system.

On the one hand, metal adds rigidity to the rafter structure, but on the other hand, it reduces the service life of wooden parts. Condensation settles on metal platforms and supports, which leads to rotting and damage to the wood.

Advice. When installing a rafter system made of metal and wood, care must be taken to ensure that the materials do not come into contact with each other. You can use moisture-proofing agents or use film insulation

In industrial construction, metal rafters made of rolled steel (I-beams, T-beams, angles, channels, etc.) are used. This design is more compact than wood, but retains heat less well and therefore requires additional thermal insulation.

Choosing a rafter system: hanging and suspended structures

There are two types of rafter structures: hanging (spacer) and layered. The choice of system is determined by the type of roof, floor material and natural conditions of the region.

Hanging rafters rest solely on the external walls of the house, intermediate supports are not used. Hanging type rafter legs perform compression and bending work. The design creates a horizontal bursting force that is transmitted to the walls. Using wooden and metal ties you can reduce this load. The ties are mounted at the base of the rafters.

A hanging rafter system is often used to create an attic or in situations where roof spans are 8-12 m and additional supports are not provided.

Layered rafters are installed in houses with an intermediate columnar support or an additional load-bearing wall. The lower edges of the rafters are fixed on the external walls, and their middle parts are fixed on the internal pier or load-bearing pillar.

Installation of a single roofing system over several spans must include spacer and layered roof trusses. In places with intermediate supports, layered rafters are installed, and where there are none, hanging rafters are installed.

Features of arranging rafters on different roofs

Gable roof

A gable roof, according to building codes, has an inclination angle of up to 90°. The choice of slope is largely determined by the weather conditions of the area. In areas where heavy rainfall prevails, it is better to install steep slopes, and in areas where strong winds prevail, flat roofs are installed in order to minimize the pressure on the structure.

A common version of a gable roof is a design with a slope angle of 35-45°. Experts call such parameters the “golden mean” of consumption of building materials and load distribution along the perimeter of the building. However, in this case, the attic space will be cold and it will not be possible to arrange a living room here.

For a gable roof, a layered and hanging rafter system is used.

Hip roof

All roof slopes have the same area and the same angle of inclination. There is no ridge girder here, and the rafters are connected at one point, so the installation of such a structure is quite complicated.

It is advisable to install a hip roof if two conditions are met:

• the base of the building is square in shape;
• in the center of the structure there is a load-bearing support or wall on which it will be possible to fix a rack that supports the junction of the rafter legs.

It is possible to create a hip roof without a stand, but the structure must be strengthened with additional modules - tie-down stands.

Hip roof

The traditional design of a hip roof involves the presence of slanted rafters (diagonal) directed towards the corners of the building. The slope angle of such a roof does not exceed 40°. Diagonal runs are usually made with reinforcement, since they account for a significant part of the load. Such elements are made from double boards and durable timber.

The joining points of the elements must be supported by a stand, which increases the reliability of the structure. The support is located at a distance of ¼ of the length of the large rafters from the ridge. Shortened rafters are installed in place of the gable roof gables.

The rafter structure of a hipped roof can include very long diagonal elements (more than 7 m). In this case, a vertical post must be mounted under the rafters, which will rest on the floor beam. You can use a truss as a support - the beam is located in the corner of the roof and fixed to adjacent walls. The truss truss is reinforced with struts.

broken roof

Sloping roofs are usually created to accommodate a larger attic. The installation of rafters with this roofing option can be divided into three stages:

1. Installation of a U-shaped structure - supports for purlins that hold the rafter legs. The base of the structure is floor beams.
2. At least 3 purlins are installed: two elements run through the corners of the U-shaped frame, and one (ridge purlin) is mounted in the center of the attic floor.
3. Installation of rafter legs.

Gable roof: do-it-yourself rafter installation

Calculation of inclination angle and loads

Of course, you can calculate a gable roof yourself, but it’s still better to entrust it to professionals in order to eliminate errors and be confident in the reliability of the structure.

When choosing the angle of inclination, it is necessary to take into account that:

• an angle of 5-15° is not suitable for all roofing materials, so first choose the type of coating, and then calculate the rafter system;
• at an angle of inclination over 45°, material costs for the purchase of components of the “roofing cake” increase.

Load limits from snow exposure range from 80 to 320 kg/m2. The design coefficient for roofs with a slope angle of less than 25° is 1, for roofs with a slope from 25° to 60° - 0.7. This means that if there are 140 kg of snow cover per 1 m2, then the load on a roof with a slope at an angle of 40° will be: 140 * 0.7 = 98 kg/m2.

To calculate the wind load, the aerodynamic influence coefficient and wind pressure fluctuations are taken. The value of the constant load is determined by summing the weight of all components of the “roofing cake” per m2 (on average 40-50 kg/m2).

Based on the results obtained, we find out the total load on the roof and determine the number of rafter legs, their size and cross-section.

Installation of Mauerlat and rafters

Do-it-yourself installation of rafters begins with the installation of a mauerlat, which is fixed with anchor bolts to the longitudinal walls.

Further construction of the structure is carried out in the following sequence:

Installation of rafters: video

Methods for connecting rafter structure elements: video

In previous articles that described the structure of the roof, we already said that the hanging rafters rest with their lower ends on the mauerlat, and the upper ends of adjacent rafters rest (either directly or through a ridge board) against each other. In the most simplified version, this is shown in Fig. 1:

Figure 1

I think it is obvious to everyone that with such an arrangement, bursting loads appear on the walls. To reduce them, tie downs are added to the truss. But let's talk about everything in order.

As an example, let’s take a house with a semi-attic in the Volgograd region. The sum of snow and wind loads is 155 kg/m2. The dimensions of the house box are 8x10 meters. The thickness of the walls is 50 cm. The angle of inclination of the slopes is 40° (see Fig. 2):

Figure 2

STEP 1: We install. In this design, in addition to the usual loads, pushing forces will act on it, tending to move it from the wall. For more reliable fastening, you can add metal fastening plates to the anchor bolts (or studs) (see Fig. 3). The plates can be secured to the wall, for example, with frame anchors, and to the Mauerlat using nails, self-tapping screws, and wood grouse.

Figure 3

STEP 2: We determine the required section of the rafters. We carry out the calculation in the “Arch” tab (see Fig. 4):

Figure 4

The cross-section of the rafters is taken to be 50x200 mm in increments of 60 cm.

A question may immediately arise here. Where do we get the distance from the ridge to the tie rod? For us it is 2 meters. Earlier on the site we already said that before we start building a roof, we need to make a drawing of it on paper, always to scale (with all proportions respected). If you know how, you can draw on the computer. Further, using this drawing, we determine all the dimensions and angles that interest us.

Tie-downs are installed between hanging rafters to reduce bursting loads on the walls. The lower the tension, the more benefit it will provide. Those. the less bursting load there is on the walls. But since in our example the tie rods also serve as ceiling beams for the attic floor, we determine the height of their location based on the ceiling height we need. I took this height of 2.5 meters (see Fig. 5):

Figure 5

STEP 3: We make a template for the lower cut of the rafters. To do this, we take a piece of board of the required section about a meter long, apply it to the mauerlat at our angle of inclination of the slopes of 40° (focus on the pediment) and make markings, as shown in Figure 6:

Figure 6

We draw the vertical and horizontal lines we need (shown in blue) using a level. The depth of the cut is 5 cm.

So, let's make a template.

STEP 4: We install a ridge board, through which all the rafters will be connected to each other. First you need to outline the location of its installation.

We take the template we made earlier and apply it to the Mauerlat. We are interested in the size shown in Figure 7 (here it is 18 cm):

Figure 7

Let's call the lowest point on the Mauerlat point “A”.

We transfer the resulting size to the top of the pediment, make markings in accordance with Figure 8:

Figure 8

We will designate the lower right corner as point “B”. Now we can measure the distance from the attic floor to point B (the length of the temporary racks).

We install strictly vertically temporary racks from 50x200 boards and place a ridge board of the same section on them. Under the racks to fix them, you can put a board secured with simple dowel nails to the floor slabs (see Fig. 9). There is no need to fasten it too much, then we will remove it. The distance between the posts is no more than 3 meters.

Figure 9

We attach the ridge board to the gables with metal brackets. The stability of the racks is ensured by the jibs.

Perhaps you could see somewhere how hanging rafters are installed without a ridge board (see figure on the left). I am very familiar with this method; we did this before too.

But when we tried the option with a ridge board, we settled on it. Despite the fact that it takes some time to install the racks and ridge boards, subsequent installation of the rafters is much more convenient and faster. As a result, in time you win. In addition, the design is more stable and more geometrically smooth.

STEP 5: We manufacture and install rafters.

We make a rafter like this: we take a board of the required length, apply a template to one end, mark it and make the bottom cut. Then use a tape measure to measure the distance between points “A” and “B” (see Fig. 7-8). We transfer this size to our workpiece and make the top cut. The angle we need for the top cut is on our template (see Fig. 10). For us it is 90°+40° = 130°

Figure 10

This is how we install all the rafters (see Fig. 11)

Figure 11

The connection of the rafters with the Mauerlat here does not look the same as it was, for example. I think you already understand that this is due to the presence of bursting loads, which were not present in that version. However, in future articles you will see that this option is just one of the possible, and not the only correct one. We will also use cuts that are more familiar to us. The main thing is to securely fasten the rafters to the Mauerlat.

At the top point, the rafters will protrude beyond the ridge board. You can drive small bars between them, or you can leave them as is. This, in principle, does not play any role (see Fig. 12):

Figure 12

We fasten the rafters to the ridge with nails or self-tapping screws. It is not necessary to install any additional fasteners here. In general, in this design, thanks to the lower gash, the rafters seem to be sandwiched between the Mauerlat and the ridge board.

STEP 6: We install the tightening.

We make them from boards of the same section as the rafters. It is not necessary to make any cuts or cuts here. We make the puffs overlapping the rafters. We fasten them with several nails and tighten them with a threaded rod with a diameter of 12-14 mm (see Fig. 13):

Figure 13

Thus, we install all the tightening and remove our temporary stands on which we placed the ridge board:

Figure 14

Now you can guess the purpose of the small windows in the upper part of the pediment. Through them, ventilation of the insulation will be carried out, which will lie on the ceiling of the semi-attic floor (between the puffs).

STEP 7: We attach the eaves overhang fillets to the lower ends of the rafters (see Fig. 15). We make them from boards with a section of 50x100 mm. We make the length of the filly such that we get the eaves overhang of the width we need (40-50 cm), and so that it overlaps the rafter by at least 50 cm. We fasten the filly with several nails and tighten it with 2 threaded rods. In the middle part, for additional support on the wall, you can fasten a small block to the fillet with nails or self-tapping screws.

Figure 15

Please note that at the junction of the overhang fillet with the mauerlat, we do not make a cut on it, because this will reduce its already small cross-section. Here we first make a small cut in the Mauerlat itself (see Fig. 16):

Figure 16

To make the cornice even, use lace. Place the outer fillies first, then pull the string between them and place the rest. In Figure 17, the lace is shown in blue.

Figure 17

Step 8: We already know the following steps from previous articles. We place the fillies on the pediment and attach the wind boards (see Fig. 18):

Figure 18

STEP 9: Now we can leave the cornices as they are.

Let's look at another version of the eaves overhangs (see Fig. 19):

Figure 19

These “earrings” are made from inch boards 10-15 cm wide. We fasten them with self-tapping screws.

Thus, now all we have to do is sew the siding belts to the bottom of the eaves; Having secured the protective film to the rafters, make a counter-lattice and sheathing; cover the roof with roofing material. We discussed these steps in previous articles. I think there is no point in repeating myself here and when considering other roof designs in the future.

Among the main stages of roof construction, the construction of its frame - the rafter system - is considered particularly important. This is due to the fact that during operation the roof is under the influence of very serious constant and periodic loads - snow, wind and others.

The production of rafters and the subsequent installation of a supporting structure is the cornerstone of roof construction. In fact, it is a load-bearing “skeleton” that takes on all the loads that the roof experiences. Thus, it is the rafter system that largely determines the level of protection of the building from all kinds of influences.

Types of rafters

The extreme importance of the supporting structure dictates a special approach to the choice of its type, material of manufacture and other important details. All of them are determined at the design stage of the structure.

Roof trusses are usually made of wood or metal. In rare cases, they are made of reinforced concrete.

Metal trusses arrive at the construction site ready-made, manufactured in a factory. They are lifted using a crane and then secured by welding.

The manufacturing method of wooden rafters is more varied:

• they arrive ready-made, made in the factory;
• the structure can also be assembled on a construction site from individual elements manufactured in a factory;
• production of a rafter system directly at the site under construction from elements cut on site.

The use of factory-made blanks requires maximum compliance with the project, since it will be very difficult to remake finished trusses or change the dimensions of parts, and in some cases, simply impossible.

Note

Nevertheless, this solution has an undoubted advantage - with properly constructed walls, installing the frame is no more difficult than assembling a children's construction set.

Finished factory products are mainly used in the construction of complex roofs. For example, this is how a frame is assembled over a bay window. As for prefabricated buildings, during their construction the trusses are supplied as a set.

If you decide to follow the last option, make and assemble the rafters yourself, you first need to study all the terminology associated with the roof, so that confusion does not inadvertently lead to unpredictable negative consequences.

Main components of the rafter system

The main component of the truss structure is the truss. It is a flat structure in the shape of a triangle. What elements it consists of and the number of components in the frame structure depends on the characteristics of the roof, say, type or dimensions.

Let's note some of the main components:

• Rafter legs (rafters) - lathing is stuffed onto them, on which the roofing covering is laid. The truss is formed by two beams. Connected at the ridge, they form a triangle. Their slope coincides with the slope of the roof slopes.
• The tie is a crossbar that holds the rafters together horizontally, which prevents the rafter legs from moving apart to the sides under loads. Tightening is necessary in the construction of hanging rafters.

• The grip is used in inclined rafters. It connects the rafters horizontally, increasing the stability of the truss.
• The bolt resembles a puff, but it works on a different principle - instead of stretching, it contracts. The transom holds the rafters together in the upper section.
• The stand additionally fixes the rafters horizontally.
• The brace provides the system with additional stability. This element is installed at an angle.
• Fillies are used to lengthen rafters when creating overhangs.

Sequence of actions when installing the rafter system

Working at height is not very conducive to numerous fittings, so the roof structure must be carefully thought out in advance and calculated. This will make roof installation much easier.

The rafters are of the same type in their design, so to obtain rafters from a wooden beam, it is advisable to use a template. Knowing all the required dimensions, it is not difficult to make. This should be an exact horizontal copy of the truss, which is formed by the rafters in the vertical plane. It can be done in several ways.

The template for the rafters can be made to suit such roof parameters as its slope and the dimensions of the building.

Using a similar device and a pencil, typical cuts are marked on the workpiece in the following sequence:

• The ridge part of the rafter leg. The template is applied to the workpiece and a cutting line is drawn.
• Length of the ramp. Taking the lower point of the ridge part as the starting point, set aside a distance equal to L (the length of the slope) and mark point C. Then apply a template and draw a horizontal line of the flange of the rafter tooth.

• Marking the tooth. Along the resulting line, a segment CA is laid, which is equal in length to the thickness of the beam that forms the upper frame in the wall structure. Then, according to the template, line AD is drawn, which should be parallel to the “ridge” cut. Obviously, point D will be located on the lower side of the future stop. In this way, a triangle ACD is obtained, which will actually be the tooth of the rafter.
• Overhang marking.

Having marked one rafter, the rest are made using a technological rail, onto which the control points are transferred.

You can use another option.

• To make a template, inch boards are used. They should be 100 - 150 mm longer than the designed rafter length. This makes it possible to adjust, if necessary, the connection points with the harness.
• The two boards are sewn together at the top using a nail or bolt. Such a connection will not prevent them from rotating freely around the connection point. The resulting design will resemble scissors.
• A rail is installed in the middle of the future gable and the design height of the trusses is noted. Another mark placed above marks the height of the tooth, that is, the length of the vertical that connects the base of the tooth and its top.
• Now you can determine the angle of inclination of the slope. To do this, the “scissors” are positioned with their free edges so that each board rests at an angle into the socket of the future tooth.
• The connection point and the top mark on the rail, which determines the total length of the rafter leg and tooth, are combined.

• The height of the tooth is measured from the top of the lower corner of each rafter. The template blank is lowered downwards, then the tooth is cut out according to the markings.
• Next, the workpiece is returned to the roof again, then the teeth are inserted into the corresponding sockets. It cannot be ruled out that the top of the template and the mark on the staff will not coincide. In such cases, you need to pull out the fixing nail and correct the position of the top. The mark must be made again.
• After the adjustment of the top is completed, a line of their future joint is drawn vertically on the boards.

The rafters are cut both on the ground and on the floor of the house. Both options have their pros and cons: it is certainly more convenient to work on the ground, but assembly on the roof allows you to try on the finished part on the spot and, if necessary, correct errors.

Truss assembly procedure

It is recommended to pre-assemble the end trusses without permanently connecting them. The fact is that they are the ones who ensure the correct geometry of the roof, therefore their installation must be treated with particular care: the pair must be measured repeatedly and, if necessary, adjusted.

The correct installation is checked as follows. The bottom corner of each of the temporarily fixed trusses is connected with twine to the top of the opposite corner. Thus, diagonals are formed on the slope plane. Now you can check the geometry of the ramp.

On roofs that are angular, broken or have other complex shapes, measurements are taken on all flat planes present on it.

One of the difficult moments in building a frame house, which some novice builders are faced with, is the question of how to correctly make cutouts in the rafters of the house. If you carefully study the material and the experience of experienced builders, it turns out that making them is quite simple.
So that the cutouts in the rafters do not confuse you, I am writing this article.

When writing this article, I relied on an experienced American carpenter. I simply translated some parts of the article, wrote the technical part in a similar way, but with my own dimensions, in the metric system and without a construction calculator (not everyone has a calculator), plus I slightly changed the calculation scheme (since, again, not everyone has a calculator ). This article has become more adapted for Russian realities.
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Rafter system of a frame house

When I was a young carpenter (or should I say carpenter's assistant), I admired the skills of roofing carpenters. They effortlessly made complex cuts in the rafters of a frame house, knowing only the dimensions of the roof. This puzzled me.
In those years, I tried to repeat their actions, but failure overtook me over and over again. Then the senior carpenter took me with him to one of the roofs and helped me mark and cut the rafter system using a carpenter's square and the roofer's Bible (there is such a very popular book in America, you can buy it on Amazon, Larry Hone used exactly this in his film - translator's note). This experience inspired me to master the art of making correct cuts in the rafters of frame houses. I can't say that I have become a master of this business, but I have come a long way and have figured out a little about how to do it correctly.

For more comfortable calculations, you will need a construction calculator or a special application for your smartphone.

Let's move on to measurements

(I'll show you how to calculate everything manually, without a calculator - approx. translator).

Here are the measurements of the rafter system we need: rafter angle(Pitch) rise(Rise) mileage(Run) and diagonal(Diagonal). If you know the dimensions of any two of these four dimensions, you can easily find all the others.

Watch the video for more details:

(for those who understand English - approx. translator)

Look at our roof model (picture above), initially we need to know the dimensions of its two elements: building width And ridge board thickness.

The width of the building, for example, will be 8.8 meters. (8.75 meters and 0.05 m inch paneling on each side of the house):

Each rafter stands on its own half of the building and is connected to each other on a ridge board. Therefore, you need to subtract from the total width of the building ridge board thickness, otherwise you will make a mistake when calculating the length of the rafters. Let's take its thickness 50 mm.

We consider the total width of the building without ridge board: 8.8 meters – 0.05 meters (50 mm) = 8.75 m.

Now you need to divide the result by 2 to get "mileage» (Run) of each rafter.
We count "mileage" each rafter: 8.75m/2 = 4.375m.

Now we need one more element that we know in advance, this is the roof pitch angle. In our case, let it be 6 to 12 (26.5 degrees– approx. translator).

Since our roof has a slope 6/12 , which means rise in our two times less, how mileage(since 6 is 2 times less than 12).
We count rise: 4,375/2 = 2,187m.(let's round off half a millimeter)

We count diagonal:
Run(“2)+Rise(“2)=Diagonal(“2) (“2”) - I designated “squared”.
19.1406 + 4.7851 = Diagonal("2)
Diagonal= square root of 23.9257
Diagonal = 4,891 = 4 meters 89 cm 1mm

Rafter template.

The next step after calculations is making a template for rafters. To do this, you need to screw the bosses to your square (this is more convenient, but you can do without it) at 6 and 12 inches (or 15 and 30 cm in the metric system).

Now I apply a square to the side of the board along its width and begin to mark the place of the cut at the top of the rafter (at where it joins the ridge board– approx. translator). Please note that most cuts in frame house construction are done exactly this way: the board is cut lengthwise on the thin side, and widthwise in a horizontal position.

I make this cut at the top of the rafter using a circular saw (in the video) before marking cutout at the bottom of the rafter(so-called "bird's beak" or entering corner or notch - approx. translator). This is convenient because I can hook the end of the tape measure to the saw at the top and one mark the distance on the rafter to the “bird’s beak” (see below in the picture)

Now we measure the “diagonal” from the top point of this line 4 meters 89 cm 1 mm.

Then, using a regular carpenter's square (some carpenters prefer the Swanson protractor measuring square, you can read about it on the forum - approx. translator), I draw a parallel line to the first saw across the rafter. This line represents the plumb line (i.e., parallel to the wall and perpendicular to the floor of a frame house) on the rafter at the edge of the building.

The following short video will show you how to draw such a line using an alternative Swanson square:

I personally love my Swanson angle very much; it has been my faithful assistant in construction since the very first days.

So, "bird's beak" starts from this line. If you are building and you have clear dimensions of rafters and cuts (project), you must select at this stage the size of the horizontal cut, the plane of the rafters that lies on the ceiling (see the bottom photo on the bottom left). Canadian codes require this saw to be at least 38 mm.

The horizontal size should be such that the rafter does not weaken too much, i.e. the cut did not go further than a third of the board (see picture below).

According to the author, this is the fastest way to mark this cut (pictured above). To do this, you need to turn the square 90 degrees to the previous saw and press the bosses against the board, while slowly moving the square towards the top of the rafters until the required distance is from the drawn line and the angle of the board in the direction of the square (in the original it was 4 inches).
There is another method (in the picture below).
We apply the square to the drawn line and move the square along the vertical line until the desired horizontal scale mark (110-120 mm) touches the edge of the board.

Let's look at our case.

Let's take for example that our rafters are made of boards 200×50mm. For her, with a roof slope angle of 6 to 12, it will be safe to make a horizontal cutout 120 mm. In this case, it will be vertically subtracted from the board 60mm(since with such a slope we always have a vertical dimension that is 2 times smaller than the horizontal, remember?) and the rafter will definitely not be weakened.
And here are some interesting estimates for notches at other angles and different widths of the board (according to one authoritative frame builder from the forum):

We consider the “rise” in reality.

Yes, we already have the “lift” size and it is equal to 2.1875 meters. But let's look at our rafter system diagram. Obviously, our size is not the same as that of the board that supports the skate (even if only temporarily).

First we need to add to our “lift” the so-called H.A.P., which is equal to the size remaining vertically above the wall trim below the bottom of the rafters, where we made the vertical cutout (pictured above).

We consider ours H.A.P.: 223.6 mm (full width of the board at an angle of 26.57 degrees) subtract 60 mm (our vertical cut) = 163 mm.

Now to our rise (2.1875 meters) add H.A.P ( 0.1635 m.), it turns out 2.35 m.

We found ourselves at the highest point where the rafters meet at the ridge board. But that's not what we need. Now we will finally get the height of the required board for the ridge board.

Height ridge boards: 2.35 m subtract the height of the ridge board 200 mm = 2.15 m, i.e. 2 m 15 cm.

Find the full length of the rafters.

After all this fuss, I would like to know the length of the ENTIRE rafter, i.e. with eaves overhang. Everything is simple here.

For example, we need overhang 80 cm, This means that with a roof 6 to 12 down, the overhang drops by ½ of the length of the overhang, i.e. 0.4 meters.

We count overhang diagonal= 0.16 (0.4 squared) + 0.64 (0.8 squared) = 89.5 cm

Total total length of each rafter with overhang = 4 meters 89 cm 1mm + 89 cm 5 mm = 5 meters 78 cm 6 mm.

A small bonus to the text.
Square Swanson deserves its own video (below). And for those who are inspired by it and decide to buy it, be sure to have at hand a translation of the book that comes with it for sale in English. language.

So, I hope that after reading this article it has become much clearer to you how to properly make cuts in the rafters of your frame house. If you still have questions, please ask.

How the site can help you

1. Make it convenient and understandable for you (or help in designing a frame house).

4. Bring it to you from Belarus

5. 1. Consult on any issue of frame house construction. 1 hour - 1000 rubles(or 2 weeks of answers in text format also for 1000 rubles)

You can contact me via email or phone +79200221811

J. Carroll (Canada)

BUILDING one

CONSTRUCTION OF THE ROOF

Building without help is not easy. There you need to support, and here you need to tighten up. Only a magician can be in two or even three places at once. Won't it burst? The author of this article proves by his example that one person can also build a house. Well-thought-out technology and special devices allow this to be done very effectively. Today he talks about how he built the roof alone.

Erection of the roof is the most important and difficult stage of construction. You have to work at heights, and any kind of fittings are practically impossible here. This means that everything needs to be carefully calculated and the design thought through so that the installation of the roof becomes less labor-intensive.

Work traditionally begins with the preparation of rafters. To do this, I use a template made for the specific parameters of the roof (the angle of the slopes and the overall dimensions of the building). This device (Fig. 1) allows you not only to mark typical cuts on workpieces, but can also serve as a guide when working with a circular saw. The sequence of marking rafters using a template is shown in Fig. 2.

Rice. 1. Template for rafters. Attach with screws

Guide strips are nailed on both sides of the template

I start working on the rafters by installing the ridge girder. I assemble the support posts for it from two boards. This not only increases the rigidity of the supports, but also simplifies future installation work. Since the boards are knocked down with an offset in height, the ridge beam is securely fixed in the “saddles” of the posts. I raise the purlin in stages, and my assistant is replaced by two pairs of L-shaped brackets and clamps (Fig. 4).

I attach the first pair of brackets to the racks at a height of about 1 m from the floor and lay the purlin on them. To prevent it from jumping off the shelf, I temporarily secure its free end with another clamp. Then I install the second pair of brackets and raise the ends of the purlin one by one to a new level. I repeat the process until the timber “sits into the saddle.”

Having marked the first rafter, then I use a technological rail with control points C, D, E and F transferred to it (Fig. 3). For each subsequent rafter, I first file the ridge part according to the template, then measure the distance corresponding to the length of the slope, and finally I apply a technological strip to point C and transfer points D, E and F to the workpiece. All that remains is to draw the necessary lines according to the template, and the marking is complete .

However, the most labor-intensive operations are associated with the installation of the supporting roof structure. For roofs with slabs

54 Tips from professionals No. 109

Rice. 2. Marking the rafters.

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Step 1. Marking the ridge part of the rafter Attach the template and draw a cutting line with a pencil.

Step 2. Marking the length of the slope. Set aside a distance from the bottom point of the ridge cut that corresponds to the selected length L of the slope and get point C. Attach the template and draw a line of the horizontal flange of the tooth with a pencil.

Step 3. Marking the tooth. From point C, mark on the resulting line the distance corresponding to the thickness S of the beam

the top frame of the wall, and then, using a template, draw a line parallel to the “ridge” cut through the resulting point A and get point D on the bottom edge of the workpiece. Triangle ACD - rafter tooth.

Template of the cross section of the front plate B

Step 4. Marking the rafter overhang. At a distance corresponding to the thickness of the outer wall cladding, draw a line parallel to segment AD and obtain point E on the bottom edge of the workpiece. Without moving the template, draw a line along the other side of the triangle - this is the lower edge of the rafter overhang. Before lowering a perpendicular from the top edge of the workpiece onto it and getting point B, use the template for the cross-section of the frontal board covering the rafter overhangs - it should “fit” inside the contour of the workpiece.

When building a rafter system, it is important to monitor every detail to ensure the reliability of the structure. Particular attention is paid to the attachment point of the rafters to the Mauerlat. It is in this place that the main part of the load is transferred to the load-bearing walls. In this case, it is important not only how to fasten what to use, but also the accuracy of the cut. After all, if the board is not fully supported, then it can break and lead to the collapse of the roof. In this article we will look at how to cut rafters and what methods exist for this.

Types of fastening rafters

Depending on the design solution, the presence of internal walls and the design load, various types of fastening are used. Each of them implies its own option for preparing rafters for joining with the Mauerlat. The three main mounting methods are listed below:

• hard;
• layered;
• sliding.

We will not consider the last option, since when using it there will be no need to make cuts. It is usually used when installing roofs on houses made of timber. It is most suitable, since wooden walls shrink over time. Because of this, the rafter system may change geometry and leaks will appear.

In other options, you will have to make precise cuts. You will need precision measuring instruments, a construction pencil and an electric or chainsaw.

The strength of the roof depends not only on how correctly the cuts were made. Consider the following tips:

1. For rafters, select high-quality materials, since even if you make precise cuts, the block may not withstand the load. You can’t save money here, as this part takes all the load on itself.
2. The mounting points with the Mauerlat must be free of wood defects, such as knots. Although they are stronger than wood, turbulences form around them, which break at the slightest load.
3. When installing a roof, do not hesitate to ask for help, as this is a dangerous and responsible task.

A well-made junction between the rafter leg and the Mauerlat guarantees a long service life of the structure.

Cutting out a seat

It is important to understand that it is impossible to make a perfect cut on a construction site. The reasons may be different: lack of high-precision tools, uneven position of the Mauerlat, inconvenient position, and so on. Therefore, relative to the design value, the angle of inclination of the slope may change. The main thing here is to maintain a single line of rafter position.

The easiest way to make the same cut on the rafters is to use a template. True, this option is not suitable in all cases, as roofs are often uneven. Then you will have to calculate the angle and location of the cutting on each rafter individually.

For the base of the template, take a piece of board, a piece of fiberboard or plywood, even thick cardboard will do. On the workpiece, draw a line from the bottom edge at a distance of no more than a third of the width of the rafter. The same line must be drawn on all the beams that you plan to trim. The fact is that cutting deeper is not recommended due to loss of strength. Next, mark the points at which the rafters will be adjacent to the mauerlat, make a perpendicular line relative to the previous line.

Now let's move on to making the template, determining the angles of the vertical and horizontal parts of the notch. To do this, attach the workpiece to the end of the Mauerlat, maintaining the slope of the future roof. Opposite the corner there should be a point of intersection of the lines that were made before. Draw the lines of the triangle and cut out the resulting template.

Before transferring the markings to the rafters, check the accuracy of the finished product. Walk along the roof and check the degree of connection along the entire length of the Mauerlat. Make adjustments if necessary, but don't expect it to be perfect. Differences of 2-3 millimeters are acceptable.

Maximum concentration is important so as not to go beyond the outlined boundaries. If you are not confident in your own abilities, then use a hand tool. This way you will reduce the percentage of defects and the time for rework.

The second cut is made with an ax, since the power saw can be stuck. This also requires skill and strength. It is important to make sure that the ax is quite sharp, then the job will work better and you can avoid chipping.

Finally, check the resulting cut against the template and make adjustments if necessary. After which you can install the finished rafter leg or make seats on the remaining parts.

Trimming for direct joint with Mauerlat

A simpler option is to make a butt joint. To do this, you need to determine the location of the cut and its angle of inclination. For this purpose, two options can be used: theoretical and practical.

For the theoretical method, you need to have a good understanding of geometry and calculate the desired angle on paper. Divide the distance from the ridge to the eaves by the length of the rafter. So, you will get the cosine of the required angle. In order to transfer it to the workpiece, you can use either a miter saw or a special square.

If you don't have a special tool at hand, make a simple template. Take a durable material, such as chipboard. On the sheet, mark 500 mm along the bottom edge, then determine the tangent of the required angle and multiply by the measured length. This will give you the second side of a right triangle. By marking all the boundaries and cutting out the workpiece, get the desired angle. The sawed-off parts can be assembled immediately or you can wait until the entire set is completed.

In practice, you can easily mark a separate rafter by attaching it to the design position. To do this, position the beam so that its lower part is flush with the Mauerlat. Draw a horizontal line from the corner to the bottom of the rafter; it should be strictly parallel to the wall. Now you can safely saw off with any available tool and install the part. The remaining part will serve as a template for the remaining rafters only if the base is level.

Knowledge of geometry helps not only in determining the angle of the rafter leg, but also in determining the height of the roof, the length of individual elements, and so on.

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The roof is of great importance for the integrity of the entire house. Therefore, many are interested in how to properly assemble a rafter system so that it is reliable and does not have to be repaired in the near future. There are many types of roofs, some of them can be seen in the photo, but the most popular are single-pitched and double-pitched structures. Let's figure out how to make a rafter system correctly.

Types of roofs

Before moving on to how to make a rafter system, you need to understand what the common types of roofs are.

A pitched roof is the simplest; even a person who does not have much experience in construction can cope with its creation. However, this type of roofing is used mainly in the construction of commercial buildings. For residential buildings, gable or mansard (sloping) roofs are usually made. These structures are more complex, but you can easily handle them on your own if you know how to make gable roof rafters and follow all the recommendations of specialists (read: "").

The most reliable roofs are hip roofs; they can withstand even enormous loads. They are recommended to be done in regions where there is a lot of snow and strong winds often blow. But their design is very complex, so it is better to entrust their construction to professionals.

A hipped (hipped) roof is used in the construction of square buildings; in its design, it is a type of hip roof.

The most complex roof is a cross roof. During its construction, complex structural elements are used - valleys (grooves). These diagonal auxiliary rafters are installed as additional elements. When building such a complex roof, haste is unacceptable. The bulk of the snow accumulates in the area of ​​the valleys, and the reliability of the roof depends on how to make rafters in these places.

Each type of roof consists of rafters and roofing. The rafters are the load-bearing part of the roof, and the roof surface is the enclosing part.

Types of rafters

Before laying the rafters, you need to learn about their design features and decide on the installation option.

There are two types of rafters: layered and hanging .

Hanging rafters - These are inclined beams installed on supports with different heights. The support can be the external walls of the house (in the case of a pitched roof) or both internal and external walls (in the case of a gable roof). The rafter legs do not have to be laid in the same plane opposite to the slopes. They can be mounted alternately on the ridge girder. Alternate laying of rafters in the ridge area makes it possible to create a roof truss. For this purpose, all parts are connected together into a single rigid structure.

Materials for rafters

As for rafters made from boards, they are not heavy and are easy to install. You can easily work with this material yourself, without resorting to outside help. Many experts do not advise making connections with nails - it is better to use self-tapping screws. If the work will be carried out using nails, do not forget about linings and liners.

As for how to build a rafter system, it is better to use notches to connect the racks to the purlin or beam.

Installation of the rafter system with your own hands, details in the video:

Options for connecting the rafter system

The rafter system can be connected in three ways:

• struts;
• stands;
• simultaneously struts and racks.

How to properly make rafters depends on the span between the outer walls. A 10x10 centimeter beam is used to create a ridge girder. The bench and mauerlat can be made from logs by cutting them into two edges, or by taking a 10x10 centimeter beam.

When designing a ridge assembly, it is necessary to nail special clamps made of steel strip to the mauerlat and purlin with large nails, taking into account. You don’t have to use steel clamps, but then you need twists made of thick wire with a diameter of 6 millimeters.

Regarding how to make a brick or stone house, you need to lay a mauerlat on the masonry. To secure it securely, it is recommended to place a piece of log or timber about 50 centimeters under each rafter leg. Then they are attached using clamps to metal hooks, which were previously installed 30 centimeters below the Mauerlat.

Many people have a question about how to make rafters for the roof of wooden houses. Rafters in wooden buildings are laid on the upper crown of the wall. A plank roof truss can be created using a crossbar or with spans (6-8 centimeters). Its structural elements are arranged as follows. They make a single tightening using boards, the thickness of which is equal to the thickness of the rafters. For double tightening, thinner boards (from 40 millimeters thick) are used. For the crossbar and linings, 30 mm parts are used.

How to determine the section of rafters

Before laying the rafters correctly, you need to decide on their cross-section.

This parameter depends on:

• span dimensions;
• expected load (wind force, weight of snow cover and roofing material);
• pitch and installation angle of rafters (roof slope).

There is a dependence of the cross-section of the rafters on the length of the rafter leg.

It is expressed as follows:

• with a step of 300 centimeters, beams with a section of 10x12 centimeters or boards with a section of 6x14, 8x14 or 4x18 centimeters are used;
• with a step of 400 centimeters, beams with a section of 10x16 centimeters or boards with a section of 6x20, 8x20 centimeters are used;
• with a step of 500 centimeters, beams with a section of 10x20 centimeters or boards with a section of 8x22 centimeters are used.

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The roof covering must be selected taking into account the roof slope. Also, the choice of roofing material depends on financial capabilities. The greater the roof slope, the more money will be required to create the roof - this is due to the increased consumption of materials. However, steep roofs drain rainwater and snow better, so they are more reliable and will not require repairs longer. But given the huge selection of roofing materials on the market, this will not pose any difficulties.

Creating a rafter system for a bathhouse

As for how to make rafters for a bathhouse, it is better to choose a gable roof - then the building will have an attic space that can be used to store brooms and other bath accessories (read: " "). Thus, it is advisable to create a rafter system for a gable roof, it is simpler and more practical.