Installation of the roof truss. DIY gable roof
The rafter system of any object is equivalent to the value of the load-bearing structural elements of the house. The roof plays the role of a node under which the stiffening ribs of the building are assembled. Accordingly, when installing a roof with your own hands, you need to pay maximum attention to all structural units, even when using a simple option - a gable roof.
Advantages of gable roofs
There are a lot of options for pitched rafter systems. Among them, the simple symmetrical one is especially popular. Why? Here are its advantages:
- Variations are created on the basis of a gable roof to reflect the special architecture of the building.
- Simple calculations that are easy to understand.
- The one-piece design creates favorable conditions for dry interior space and unhindered flow of water, snow and ice.
- The maintainability, strength and wear resistance of a gable roof are much higher than other options.
Depending on the size, homeowners always have the opportunity to equip the under-roof space, turn it into a full floor or attic. In a word, a gable roof is the right and profitable solution for any building, be it a residential building, a summer house or a bathhouse.
Elements of the rafter system
Depending on the type of roof, the structural elements vary. Without knowledge of the purposes of each, it is impossible to arrange reliable coverage for your home. Let's look at it in detail:
Mauerlat
The basis of the rafter system. It is a beam with a cross-section of at least 150 mm, or an I-beam channel if the roof structure is metal. It is located on the load-bearing walls of the facility. Its purpose is to distribute the load of the system evenly throughout the entire structure of the house.
Rafter leg
The structural basic unit of a system. Together with others, it forms a truss system - strengthening the strength of the entire roof. It is made of wooden beams, not inferior in cross-section to the Mauerlat or profile pipes.
Rafter stand
Vertical beam or pipes. Depending on the gable roof option, the racks can be located in the center and/or sides. They take part of the weight of the entire rafter system, which is why the cross-sectional size is 150 mm.
Rafter purlins
Horizontal beams laid on the posts and under the ridge to support the rafter legs. They provide rigidity to the structure and relieve stress on the trusses.
Tightenings and struts
Connecting beam for rafters. The action is similar - relieving the tension of timber or metal and imparting rigidity to the structure.
Lezhny
Installation support for posts and struts. To reliably connect these two elements, a large cross-section beam is required - 150 mm or a thick-walled pipe of impressive diameter.
Lathing beam
Elements laid perpendicular to the rafters. They are used to install the selected roofing covering and create a multi-layer protective pie. The cross section is small - 40–50 mm.
If the intended roof structure is made of wooden beams, you should carefully consider the quality of the wood when purchasing - the timber should not have any knots and be made of soft wood.
Also, the wood must have natural moisture, otherwise it will begin to dry right in the structure of the system, cracking, deforming the roof model, depriving it of reliability and safety.
Calculation of the rafter system
A gable roof is a complex structure. The project takes into account many factors - natural nuances, wind, constant and variable loads. It is extremely difficult to make calculations on your own, without special knowledge about the climate of the area, the characteristics of the material for the manufacture of the system, and the nuances of pressure distribution.
Ideally, the calculations are left to professionals; you can choose only the coating material yourself - the following parameter depends on its type:
Tilt angle
The minimum angle of inclination of the roof relative to the parallel of the ground is 5 degrees. However, its dependence comes from the selected roofing material. For this purpose, traditional slate, corrugated sheets, flexible and metal tiles are used.
They are guided by the following rule: the steeper the slope, the more textured the roof can be.
From 5 degrees for laying rolled protective roof insulation. The number of layers matters - up to 15 degrees three-layer coatings, above - two- and single-layer.
- From 6 – ondulin.
- From 11 – slate.
- From 12 – corrugated sheets.
- From 14 to 20 – metal tiles.
- From 15 to 45 – soft roofing.
Thus, the resulting precipitation - snow, water - will not linger on the surface, although complete cleaning requires your own efforts or the involvement of specialists to install the Anti-Ice system.
Determination of rafter parameters - pitch, length, cross-section
The smaller the step, the more impressive the cross-section of the timber or the diameter of the pipes should be. As a rule, for load-bearing structures this parameter is at least 150 mm, 100 mm for country houses and related construction - gazebos, bathhouses, outbuildings.
Next, you need to set the number of rafters per slope: its length is divided by the installation step, ranging from 60 to 100 cm + 1 outer leg. Multiply the result by 2 to get the total quantity. Depending on the cross-section of the beam, the amount of rafter legs and the installation pitch vary.
The length of the rafters is simply calculated if the school knowledge about the right triangle remains in your luggage. The rafter leg is equal to the hypotenuse of the resulting figure. The calculation is as follows: A² + B² = C², where – A is the height of the roof, B is half the length of the pediment, C is the length of the rafter leg. To the resulting value always add from 30 to 70 cm for the eaves overhangs.
Types of rafter systems
Before getting to work, it is important to choose a rafter system option for a gable roof. There are few of them, each has its own advantages and disadvantages:
Hanging
Suitable only for a standard roof width of 6 m, which is the length of the rafter leg. Fastening occurs by fixing the ends to the ridge girder and the load-bearing wall. Be sure to install a tightening that levels out the tension and pressure of the structure.
In addition, they will play the role of load-bearing beams. Without them, the structure will corrode under the weight. The advantages of this option are the absolute dryness of the roof surface during the off-season, and less deformation at the time of shrinkage.
Layered
The option is suitable for any roof width. Reliability and stability are ensured by fixing the bed to the Mauerlat. Thus, the pressure is leveled by the stand, causing the tension in the rafter legs to decrease. The advantage of the system is its simplicity, but the design requires large investments - additional lumber is required to arrange the beds.
Hybrid
These systems are typical for multi-slope roofs, where the transitions are accompanied by numerous reinforcements, beams, posts, beams, slopes and other elements for the stability of the entire structure. The device is expensive and complex, so only a professional should be involved in the design and construction. At least supervise it.
DIY gable roof installation
So, when the rafter system option has been selected, lumber has been purchased, a roof design has been drawn up, you can begin to work. You cannot deviate from the sequence of stages. This threatens to delay installation and loss of structural reliability.
Mounting the Mauerlat
If the length of the timber for installing the Mauerlat is not enough, extensions are made. The ends are connected using the half-tree cutting method. Additional fasteners are anchor bolts. Do not use screws, dowels or nails - they are unreliable. Mounting to the wall is as follows:
- A distance from the edge of at least 5 cm is maintained.
- Holes are drilled along the wall to insert fasteners. Similar actions are carried out with timber.
- The Mauerlat is attached to the edge using steel pins. The fastening step is often 2 times the distance between the rafter legs. Subsequently, before installing the main units, they are guided by metal marks.
Important - before laying the mauerlat, the edge of the wall is protected with waterproofing. Spread one layer even if the house is made of wood.
Manufacturing and fastening of rafters
Roof trusses are convenient because they can be assembled on the ground into a finished structure and moved to the roof. This will reduce installation time, however, the model is heavy and lifting equipment will be required, which, naturally, will increase the cost of the project.
For budget construction, another method is suitable:
- A cut is made at the bottom and top of the rafter legs to connect to the mauerlat and ridge girder. This must be done separately with each unit, after first lifting the wood to the top.
- Places for fixing are marked on the Mauerlat and a ridge girder is installed: racks are installed along the gables, on which the timber is placed. If the length is not enough, it is increased, but in a different way, unlike the Mauerlat - a board is screwed onto the joint on both sides.
- Depending on the chosen model of the rafter system - layered, hanging - cuts are made in the ridge beam, mauerlat, or holes are drilled in them for fastening.
- Next, they begin installing the rafter legs from opposite ends of the roof, gradually moving towards the middle. It’s a good idea to pull a cord between the corners of the outer trusses to ensure that the entire horizontal part matches exactly.
- The rafter legs are connected to each other by ties and struts. Under the ridge part, at the angle formed by the rafters, wooden overlays are stuffed, and the ends themselves are tightened with bolts.
More recently, professional builders have begun to use sliding fasteners to install roofing. Metal plates reliably hold the load-bearing elements and at the same time move due to shrinkage. This neutralizes its consequences.
The work of fastening the rafters is hard and long. You should calculate the time in advance - you cannot leave the roof unfinished during the rainy season, otherwise the rigidity of the structure will be lost in the future due to absorbed moisture.
Pediments and sheathing
The side parts of the roof - gables, are made in the form of ready-made panels from boards and are completely installed at the top. There shouldn’t be any difficulties - it’s just important to carefully cut them at the required angle. The sheathing should be fastened only after the final type of roofing is known. For example:
- Under corrugated sheeting, the pitch of the sheathing beam will be 440 mm.
- The metal tiles are fixed to the sheathing in increments of 350 mm.
- A soft roof requires a continuous plywood covering.
It is important to note the places for the passage of the chimney - the sheathing should not come into contact with the brick or metal surface. The distance to the hot unit is at least 15 cm. Before installing the sheathing, the finished roof is covered with waterproofing with allowances extending beyond the edges of the walls. Then the timber is installed.
If you decide to make an insulation cake from above, then first strengthen the vapor barrier from the inside, then put the selected material into the boxes formed by the rafters. Next, waterproofing and wind protection.
Then you need to re-mark the contours of the rafters with 20*20 timber and then fill in a new layer of sheathing, along which the roofing material will be laid - the formation of ventilation ducts. This method will preserve the capacity of the under-roof space if the owners intend to use it for a specific purpose.
Flooring roofing material
Regardless of the type of roofing material, installation begins from the edges of the roof and goes up, placing one unit on top of another. This way, rain moisture will not get under the material.
The method of fastening depends on the type of material - soft tiles or tiles with a bitumen or polymer base - they are fused. Solid profiled sheets - ondulin, metal tiles - are fixed into pre-drilled holes to the sheathing, using rubber linings to seal and preserve the anti-corrosion layer.
As a result: a description of the installation of the rafter system and roof is easy only on a screen or paper. In reality, the process is complex and multifaceted. Therefore, if knowledge is not enough, it is better to invite professionals to work - their work is always guaranteed.
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When planning the construction of low-rise residential, utility or commercial buildings, most designers choose a gable roof structure. This is due to the relatively simple installation technology, increased structural reliability, effective removal of precipitation from the roof and unpretentiousness to operating conditions. However, to achieve all the benefits, you need to competently design and install rafters for a gable roof with your own hands.
Exterior view of a house with a gable roof
Gable roofs are two rectangular inclined planes (slopes) that rest on a rafter system. The side parts are made blank or windows and trim are installed on them. The main parameters of such a roof are: the angle of inclination and the location of the ridge relative to the center line passing through the walls perpendicular to the slopes. That is, a gable structure does not necessarily have to have the same slope of the slopes or have a symmetrical appearance.
Many original projects use an asymmetrical design of slopes to take into account certain climate features, or to improve the design of the facade. It is worth noting that such solutions are very original, but in practice they are quite difficult to implement. This is due to the following reasons:
- The load on the walls and foundation increases where the roof ridge is displaced. As a result, calculations can become significantly more complicated, especially when using heavy roofing materials such as slate or ceramic tiles.
- It is necessary to manufacture separate structural elements for each slope, which can significantly increase construction time.
- The pressure of wind flows can have a significant influence on the roof at large angles of inclination of the slopes. Therefore, it will be necessary to take into account the preferential direction of the winds when making calculations.
Basic elements of a pitched roof system
Before making rafters for a gable roof, you need to create a project and also study all the structural elements. You will need to design the following main components:
- Mauerlat. Ensures the transfer of the load of the roof structure to the load-bearing walls of the facility, creating its uniform distribution. The timber is made from deciduous wood such as larch, oak, ash. The minimum permissible cross-section is 100x100 mm. It is allowed to use not only solid timber, but also glued timber, but with a cross-section of 100x150 mm.
- Rafters. The main structural element, which is designed to form a load-bearing frame, absorb the load of the roofing material through the sheathing and transfer the load to the mauerlat. The distance between the rafters of a gable roof ranges from 0.6 to 1.2 m, depending on the weight of the roofing material and the amount of precipitation in a particular area.
- Puff. A special design used to fix two inclined beams of slopes at a given angle of inclination, which is mounted at a level just above the beams or slightly below the ridge. It is used in layered types of roofs.
- Rack. It is a vertically installed and firmly fixed element that performs the load-bearing functions of the roof. It is usually installed on the walls of a building to partially transfer the roof load. Gives additional rigidity to the structure.
- Run. There are two types: side and ridge. The side beam is a beam supported on posts and located parallel to the ridge beam. Allows you to prevent the slope from bending under significant loads. The ridge run is installed along the line where one slope joins another and serves as a support for the ridge.
- Strut. It represents auxiliary supports for racks, which are located at an angle of 45 0 to the load-bearing beams of the slopes in order to increase the area of contact with the racks and reduce the risk of deformation of the slope.
- Sill. Serves as a fulcrum for the strut and stand.
- Lathing. It is used to fix the rafter system in the transverse direction, transfer the load of the roofing material and its fastening, as well as provide resistance to loads in the runs between the load-bearing beams.
Helpful information! Due to increased snow and ice loads on roofs, struts for northern regions can be installed not only longitudinally, but also diagonally. Thus, a significant part of the load is carried by the racks, and not the walls of the building.
Calculation of the length and pitch of rafters
When installing rafters for a gable roof with your own hands, you need to observe a fastening step of 0.6-1 m. The choice depends on the design loads, taking into account the safety factor. The smaller the step, the stronger the structure and the greater the consumption of building materials. A large interval of 0.8-1 m can be used only when laying light roofing sheets and inclination angles of 15 0 -20 0. It is recommended to choose a step within 0.6-0.8 m.
The length of the beams, knowing the angle of inclination of the slopes and the distance between the two walls of the object, can be easily calculated using the Pythagorean theorem. However, the actual length needs to be increased by 60-70 cm, which will be used for their joining, as well as for the overhang of the slopes of approximately 0.5-0.6 m.
A gable roof is the best do-it-yourself option for an inexperienced builder. It is simple to implement, but at the same time reliable and can withstand significant loads from both wind and precipitation. She, of course, is not very beautiful, but she looks quite organic in the baths.
To do everything consciously, you need to understand the structure of a gable roof and the purpose of all its elements. Let's start in order.
Mauerlat
This is a large block fixed to the load-bearing walls around the perimeter of the building. It is this element that accounts for most of the load from the roof. And it is the Mauerlat that transfers it to the load-bearing walls.
For this element, square bars measuring 100*100 mm or 150*150 mm are used. They are connected to the walls using embedded studs. If the bathhouse is wooden, then the upper crown usually serves as the Mauerlat. For all other types of walls, a belt is made of reinforced concrete into which studs are embedded. Then the beam of the selected section is “put on” the studs and tightened with nuts. Sometimes it is additionally secured with long pins.
Since the thickness of the walls is often greater than the width of the mauerlat, its outer side can be covered with bricks. This will make the system more reliable. Only the wood needs to be wrapped in two layers of roofing felt to protect it from moisture and rot.
Rafter legs and ridge
A ridge is a horizontal wooden block located at the highest point of the roof and connecting two slopes. The rafters or rafters rest on it and on the mauerlat. Since the ridge bears quite a large load, it needs to be made of a considerable cross-section and choose durable wood.
The height of the roof ridge is determined based on the roof slope and the width of the building. The slope angle of the roof is a value that depends on climatic factors: if there is a lot of snow in winter, then you need to make the slopes steeper. The snow will come off well from them. If there are strong winds in the region, the high roof will experience heavy loads and may be damaged.
For average conditions, the optimal roof slope angle is about 35°-45°. They will not be heavily loaded by the wind, and the snow will not accumulate heavily. In addition, with this angle, you can choose any type of roofing: any of the tiles, soft roofing, slate, metal tiles.
Also remember, the higher the ridge is raised (steeper the slopes), the larger the roof area will be. And this will lead to large costs for the purchase of roofing materials and the volume of work.
Knowing the slope angle and width of your bathhouse, you can calculate the height of the roof ridge. To do this, the width of the building must be divided by two (if the ridge is in the middle and not shifted to one side or the other) and multiplied by the tangent of the slope angle (the first formula in the figure). In order not to look for the required coefficient in mathematical tables, it is written out and summarized in a simple table.
| Roof pitch angle | 5 | 10 | 15 | 20 | 25 | 30 | 35 | 40 | 45 | 50 | 55 | 60 |
| Tg A (ridge height calculation) | 0,08 | 0,17 | 0,26 | 0,36 | 0,47 | 0,59 | 0,76 | 0,86 | 1 | 1,22 | 1,45 | 1,78 |
| Sin A (rafter length calculation) | 0,09 | 0,17 | 0,26 | 0,34 | 0,42 | 0,5 | 0,57 | 0,64 | 0,71 | 0,77 | 0,82 | 0,87 |
Multiply half the width of the house by this coefficient. Get the height of the ridge for your bathhouse. For example, the width of the bathhouse is 4 meters, the angle chosen is 35°. We calculate: 4 m / 2 * 0.76 = 1.52 m - the height of the ridge from the ceiling.
Now about the rafter legs. They are made from pine or spruce bars, or better yet, larch. Section 50*150 mm or 50*100 mm. The choice of thickness of the bars depends on:
The length of the rafter leg is also calculated using a mathematical formula: the height of the ridge is divided by the sine of the angle of inclination (second formula in the figure). The sines of the angles of inclination are also in the table. Find the desired value and count. For example, for the 1.52 m ridge we found and the rafter angle of 35°, 1.52 m / 0.57 = 2.67 m will be needed.
Roof overhang and filly
But the roof does not end exactly above the load-bearing wall. It continues beyond the walls for about 40 cm. This protrusion is called the roof overhang. This is done so that the water flows further from the foundation and does not wash it away. That’s why the rafter legs are longer. If their length is not enough, they are extended with boards, which are called “fillies”.
To organize the roof overhang, boards are added to the rafters - fillies Types of rafter systems
Rafter systems come with hanging or layered rafter legs. Those hanging rest only on the outer walls of the building (on the mauerlat or upper crown). In order to increase the reliability of the system, so as not to collapse the walls, they are connected with ties (also called a lintel or crossbar). This type of rafter system is suitable for buildings of small width (less than 10 m) and in cases where there is no load-bearing wall running in the middle.
Two types of rafter systems - with hanging and layered rafters The second type of system is with layered rafters. They rest on a ridge beam and a mauerlat, but the load from the roof is also distributed onto the middle load-bearing wall, through vertical bars - purlins, which are installed at the same pitch as the rafters and rest on the bottom tie.
Do-it-yourself installation of gable roof rafters
For most baths, the system is made with hanging rafter legs - the dimensions allow this to be done. In this case, there is less consumption of lumber and less time is required for its arrangement. Most of the work can be transferred to the ground.
They make one triangle from the rafters according to all the rules and dimensions. They try it on, and then make the required number of its exact copies. The finished rafters with ties and crossbars, fastened and measured, are lifted onto the roof. There they are placed strictly vertically in designated places and secured to the Mauerlat and the ridge.
For an example of how you can make a gable roof with hanging rafters, see the video.
When the length of the roof slope is more than 4.5 meters, to increase the reliability of the system, vertical posts are installed, which support the rafter leg with one end and rest against the floor beam with the other. This is done regardless of the type of rafter installation: both hanging and layered. They also install slopes that make the structure even more rigid.
In any case, the rafters will need to be attached to the ridge beam, as well as to the mauerlat. The figure below shows options for attaching to the ridge.
It will also be necessary to attach the rafters to the mauerlat. How this can be done - see the photo below.
Sheathing device
Making a gable roof with your own hands ends with the installation of sheathing for the roofing material. To do this, a waterproofing film or membrane is rolled out along the outside of the rafters. Lay it in a horizontal direction. Start from the bottom and work your way up. The second and all subsequent rows are laid with an overlap of at least 15-20 cm. They are secured with small nails or staples from a staple gun.
After installing the rafter system, a waterproofing film or membrane is attached to it, and a sheathing is placed on top There are two ways - with or without counter-latching. The counter-lattice is stuffed along the rafters, and on top there are sheathing bars. This creates an air gap between the waterproofing and the roofing material. This option is better from the point of view that such a roof will dry out better and faster. And this is very important for baths.
Without a counter-lattice, the bars are packed directly on top of the waterproofing. There is a gap here too, but it is smaller, therefore, the ventilation will be worse. But this option is also acceptable: the consumption of materials and work is also less.
After making the sheathing, all that remains is to secure the selected roofing material.
Results
Now you know how to make a gable roof with your own hands. Of all the types, this is the simplest option that can be made by a non-specialist.
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:
Picture 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 desired 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 board, the subsequent installation of the rafters is much more convenient and faster. As a result, you win in time. 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 hem 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.
The roof is a complex and important architectural element of any building. Its construction should be treated with special attention; it must be remembered that installing a rafter system requires considerable experience in performing such work and special tools. Those who are holding carpentry and measuring tools for the first time in their hands should not undertake the task of creating a roof - the results of the activity can be very negative.
There are two types of roofs depending on the number and placement of rafter support points, but each developer can, at his own discretion, slightly change the specific design of the rafter system. This takes into account the operating conditions of the building, the purpose of the attic space, the climatic zone of the location, and the technical parameters of lumber and roofing coverings. Of course, the type of rafter system is influenced by the personal experience and preferences of developers.
Before you start making rafters, you should decide on their type, method of fastening and linear dimensions. Only in this case can you be sure of the strength and safety of the structure.
How do various factors influence the parameters of rafters?
| Physical factor | Brief description of the effect on rafter parameters |
|---|---|
| The rafters must withstand snow and wind loads. During calculations, you need to take the actual maximum values of snow cover from the tables of building codes and take into account the strength and wind rose. The data allows you to find out the total load on the roof slope depending on its area and angle of inclination. Next, you can determine the size of the rafters, their number and pitch. In this case, a safety factor must be included. The fact is that lumber does not have stable and uniform strength values; too many unforeseen factors influence these indicators. For most cases, 50×150 mm or 50×200 mm boards are used to make rafter legs. |
| Gable roofs can be layered or hanging. For hanging roofs, you need to make rafters from stronger boards. In this case, the method of fixing the elements to the Mauerlat is taken into account. If a notch is made, then the width of the boards should increase by the amount of the notch. The fact is that the cut in this place automatically reduces the width of the material that takes the load. If you make a cross cut 60 mm long on a 200 mm thick board, then only the remaining width of 140 mm is taken into account. Accordingly, if, when calculating the loads, rafters from 200 mm boards are selected, but during fastening unintended cuts of 60 mm are made, then the width of the blanks for the rafters increases to 260 mm. This remark is made for those who like to abuse various notches and cuts for the persistent areas of the ends of the rafters. Currently, there are many special devices that allow you to firmly fix the rafter in the desired position without sawing. |
| For residential buildings, rafters must have a safety margin of at least 1.4 of the design values. For non-residential buildings the coefficient is reduced to 1.2. Conclusion - the size of the rafter boards on houses is larger than on garages and other extensions. |
| Residential attics (attics) must have an insulated roof. The width of the rafters must correspond to the thickness of the insulating layer. At the same time, you need to adjust the pitch between the rafter legs depending on the standard width of the insulation. If in a given climatic zone the optimal thickness of roof insulation is 200 mm, then it is recommended to choose the same width for the rafters. Various extensions of narrow rafter legs during roof insulation are not considered the right solution. |
This knowledge will help you make the right decisions both during the manufacture of rafters and during their fixation directly on site. Mistakes in the construction of a rafter system are too expensive; you should not be overly self-confident.
What influences the choicesizes andwaysfasteningsrafters
A very important point. The task of any fixation is to ensure the stability of the connection node, while it can be stationary or have one or more degrees of freedom. This cannot be achieved without knowledge of the loads affecting the rafter legs. Loads can be permanent and temporary, dynamic and static, unidirectional and multidirectional.
- Constant vertical forces. They arise due to the impact of roofing and roof insulation materials. Due to the fact that the rafter legs are located at an angle to the vertical force, they are subject to bending and expansion loads. The magnitude of the forces is determined after constructing the diagram; based on the specific bending and expansion forces, the thickness and width of the boards for the rafters is selected. The fastenings must prevent the rafter system from spreading.
- Variable vertical forces. Appear in winter, the magnitude depends on the depth of the snow cover.
- Lifting wind forces. As a result of gusts of wind, lifting forces are applied to the roof. The dimensions of the rafter legs are not affected; the forces are taken into account only when choosing the type of fixation; it must provide for and support such loads.
- Lateral forces. The value depends on the windage of the roof. As a result of gusts of wind, lateral forces act on the rafter system. They increase bending and tearing loads. This feature also needs to be taken into account during the manufacture and installation of rafter legs.
There are options for rigid fastenings of roof trusses; for this, metal plates, corners, screws and nails are used.
Sometimes it is necessary to use floating rafter connections to compensate for changes in the size of wooden houses. For floating connections, special fasteners and bolts are used. The second allows the rafter legs at the top to rotate slightly.
Another example of a loose rafter connection is a sliding one. It is used on wooden log houses and makes it possible to compensate for the natural shrinkage of the house.
What elements are used to increase the stability and load-bearing capacity of rafters
As a result of the correct choice of the rafter system and methods of fixing its elements, the structure must be stable, compensate for natural fluctuations in linear parameters and withstand various loads that arise during operation. To fulfill the conditions during fixation of rafters, additional fixation elements can be used.
Runs
Most often they are mounted in the ridge part of the system; the upper ends of the rafter legs rest on them. To increase stability, cuts may be provided. The top connection is rigid or floating with bolts. On large roofs, purlins can be installed in the middle of the rafters or in other places with critical loads.
VertikAlinen racks
They are installed to strengthen rafters; through the use of racks, elements can be made from thinner lumber. The upper end of the vertical racks rests against the rafters, and the lower end against the beam or ceiling beams.
CornerOpores
Resists bending and expansion forces, universal use. Corner stops can be placed in any places of the rafter leg that cause concerns about strength. Due to such stops, the resistance of rafters to bending and tearing forces significantly increases.
Puffs(crossbars)
The purpose is to keep the rafter legs from spreading; they are used on hanging rafter systems. Most often they are placed in the upper part of the truss; for manufacturing, you can use boards approximately 20–25 mm thick. The fact is that they work in tension, lumber holds such forces well. The boards do not work well under compression, quickly sag and lose their original strength.
Knucklehellish
They are used in the upper ridge part of the rafters; due to the use of puffs, the strength of the joint connection is increased. Pulls can be made of wood, plywood, OSB or metal.
Lugs(stops)
They have many specific names. They are ordinary pieces of boards 30–40 cm long and 40–50 mm thick, fixed at the bottom of the rafters. They rest against the mauerlat and prevent the structure from slipping. The use of bosses allows for a rigid connection of elements without sawing down the rafters. We talked about the problems that arise in connection with sawing in this article above.
Prices for various types of timber
Options for connecting the ridge assembly of rafter legs
The ridge is one of the main and most loaded elements of the rafter system. The unit has several connection options; you should choose a specific one depending on the general parameters of the roof.
If the slopes are long, it is better not to use a ridge beam, but instead install two parallel purlins and tie-down crossbars. This design is easier to make, more stable and safe.
For a suspended roof, you should choose the most reliable methods of connecting rafter legs; these systems have a minimum number of additional stops.
Prices for various types of fasteners for rafters
Rafter fasteners
Step by stepWithThand of mouthAnew rafters
For the rafter legs, 50×200 mm coniferous boards and first-grade lumber are used. The boards cannot have traces of rot or fungus, significant defects or deep cracks. The use of low-quality lumber for the manufacture of rafter systems is strictly prohibited.
To increase the protection of roof elements from rotting, it is recommended to use fire protection.
Rafter blanks should be impregnated at least twice, and the material should be dry and clean. Processing is done on a level area in dry and clear weather.
You can impregnate with a roller, brush or pneumatic remote control. It is not recommended to use household hand sprayers - they are too time-consuming and difficult. The boards can be raised to the top after the impregnation has completely dried.
Our gable roof has a ridge girder; the vertical supports rest against a beam located on the load-bearing wall in the middle of the building.
Practical advice. If the house is quite tall and the boards are heavy, then it is recommended to make a simple device to protect the window openings from damage. To do this, two boards are knocked together in the form of a square; the length and width are selected taking into account the parameters of the opening. The device is installed on the window sill, and the rafter boards do not damage the foam blocks during lifting.
Prices for fire-bioprotective impregnations
Preparatory operations
The production of rafters begins with preparatory operations.
Step 1. Raise rafter boards into the attic. For convenience, place them evenly along the length of the building, place one end on the mauerlat, and the other on the girder. First you need to install the outer rafters on both sides of the roof of the house, stretch a thread between them and install and align all the remaining ones along it.
Step 2. Check the position of the ridge run again. It should be located exactly in the middle of the roof. Its displacement by 1–2 centimeters will not affect the strength of the roof as a whole, but will somewhat complicate the manufacture of rafters and the laying of roofing materials. In addition, an experienced builder may notice a discrepancy in the sizes of the slopes and, accordingly, the asymmetry of the roof. It is recommended to ensure that the ridge run is located along the line of symmetry, unless this is associated with great difficulties. The final decision is made by the foreman on site and depends on the magnitude of the displacement and the amount of work to correct the error.
How to align a run?
- Attach a sheathing board to the Mauerlat; it is lighter and easier to lift and fix. The second end should lie on the purlin. The board is nailed to the mauerlat with an ordinary smooth nail or screwed with a self-tapping screw.
- Climb to the top of the purlin and use a tape measure to check the distance from the edge of the purlin to the mauerlats installed on opposite walls. Work very carefully, it is advisable to use insurance. Unfortunately, in practice, few people follow safety rules, but in vain. Falls from height can cause very serious injuries.
- Center the purlin and secure the board. To increase rigidity, fix the same board on the other side of the purlin.
Now everything is ready, you can begin to manufacture and install the rafters.
Installationrafter legs
If you work alone, then you need to screw a piece of lath to the purlin at the place where the first rafter is fixed. The rafter board will be temporarily fixed to it to prevent it from sliding down.
And at this time, you can carry out work on the manufacture and preparation for connecting the upper part of the rafters.
Step 1. Lift and place the rafter board in place, using a clamp, clamp it to the previously attached batten.
Step 2. Draw lines to cut out the stop pad. This is done in two stages. First, draw a horizontal line. To do this, press the rail, square or other flat object tightly against the horizontal surface of the purlin.
Second, draw a vertical line. Now the ruler or square should be pressed against the side surface of the purlin.
Important. The width of the ruler should be no more than 2–3 cm, there is no need to make deep cuts and significantly reduce the width of the rafter leg, it loses its maximum design strength.
Make the same markings at the bottom of the rafters. Only now the ruler needs to be pressed against the surfaces of the Mauerlat.
Step 3. Remove the board and carefully cut out the seats. You can work with a hacksaw or an electric circular hand saw.
Practical advice. If the cuts are made with an electric circular saw, then it is better to cut in two steps. The first time, cut to the mark, then turn the board over and cut again to the mark. Use a hammer to knock out the cut piece, and remove the remaining protrusion with a chisel or chisel. There is no need to go beyond the line with the saw and try to cut off the lip in one go. This method increases the cut by 3–5 cm, depending on the diameter of the disk, which significantly reduces the load-bearing performance of the rafters.
Step 4. Place the prepared rafter in place and check that it is made correctly. Perform the same operations with the second leg of the truss.
Step 5. Place the rafters with emphasis on the mauerlat and purlin, tighten them with a clamp at the top. Find the middle of the purlin and transfer the line to the rafters, use a level or a construction square (only when the plane of the purlin is strictly horizontal).
Step 6. Saw two rafters along a vertical line at the same time. The boards must be tightly clamped with a clamp. Pay maximum attention to ensure that the saw blade is perpendicular to the plane of the rafters. If you saw it obliquely, the ridge joint will not fit tightly, and this reduces the stability of the rafter system and is considered an obvious construction defect.
Step 7 Remove the clamps, connect both elements in the ridge, check the correct position.
If there is a lack of practical experience in performing such work, the first leg may have a gap in the ridge part; if it is within 1–2 mm, then there is nothing to worry about. If it is more than 4 millimeters, then the element needs to be corrected. Look at which planes of the thrust pads do not allow the top cut to fit tightly. Approximately indicate the size of the additional cut. Remove the rafters and remove any interfering protrusions. Check the connection again, if gaps remain, repeat the operation. As practice shows, experience appears on the second or third rafter and no further corrections need to be made.
Step 8 Securely secure the rafter legs in the correct locations. To do this, it is recommended to use metal plates and corners; working with them is simple and easy; their strength fully meets the requirements for the rafter system.
For each pair of rafters you will need one large reshaped plate to connect the ridge assembly, two 50x50mm corners for fixing to the purlin and two 60x80mm corners for screwing to the Mauerlat. The thickness of the metal is at least two millimeters.
In the same way, install the outer rafters on the other side of the house, stretch the threads between them. One at the top and bottom and one in the middle. To prevent them from interfering during the manufacture of rafters, make a gap of about one centimeter between the thread and the plane.
Real professionals never make one rafter in the attic of a house. This algorithm of work significantly increases construction time, complicates the process itself and makes it unsafe. Working with electric tools on unsuitable sites is very dangerous; injuries from them are severe and often cause disability.
If the house is built with high quality and strictly adheres to the dimensions and rules, then the rafter legs are made according to one template on the ground. The finished elements are assembled on the roof. This technology increases labor productivity by 3–5 times, while at the same time the quality of the rafter system improves, it is more reliable and durable. Of course, the salaries of builders also increase proportionally. They work from the mine and receive money not for the time spent in the attic, but for the assembled roof.
Prices for popular models of screwdrivers
Screwdrivers
Video - Manufacturing and installation of rafters on a gable roof