Installation of a single-sided structure is often chosen for garages, outbuildings and extensions to the main buildings due to its simplicity and economy. Properly mounted ramp provides efficient removal of precipitation and snow, which is critical for the longevity of the entire building. If you plan to build such a roof, you need to clearly understand the principles of load distribution and the sequence of assembly of the nodes.
Unlike gable or valm systems, there is no skate, and the entire mass of the structure rests on two walls of different heights. Errors in calculating the angle of inclination or pitch of the rafters can lead to a deflection of the frame or a failure of the roofing cover by the wind. Therefore, before starting work, you should carefully study the method of fastening mauerlat and truss legs.
The success of the event depends on the quality of the materials used and the accuracy of the technology. load-bearing capacity The walls should be sufficient to withstand the weight of the snow cover in your area. Next, we will analyze each stage of work so that you can perform the installation without the involvement of expensive specialists.
Calculation of inclination angle and preparation of materials
Before fastening the elements of the frame, it is necessary to determine the angle of slope, which directly depends on the type of roofing material selected and climatic conditions. For soft coatings such as ruberoid or bitumen shingles, a minimum slope of 5-10 degrees is allowed, whereas metal tile or slate require a steeper stingray ranging from 20 degrees. Snow load In your area dictates the requirements for the strength of the truss system: the more snow, the steeper the slope or the more powerful the beams should be.
For the manufacture of the frame, a dry trimmed timber or a board of conifers is most often used. It is important that the wood was treated with flame retardants, which will significantly prolong its service life. The humidity of the lumber should not exceed 20%, otherwise, after drying, the structure can lead, which will lead to deformation of the roof.
Use a laser level or hydraulic level to mark the height of the walls – this will provide a perfectly flat line of support for rafters.
Calculation of the amount of materials is made taking into account the pitch of the rafters, which is usually from 60 to 100 cm. The heavier the roofing, the smaller the step should be. It is also necessary to lay a stock on overhangs that protect the walls from oblique rain.
Installation of the support bar (mauerlat)
The basis for fastening the truss system is mauerlat - a bar laid along the perimeter of the walls. On multi-level walls of a single-sided roof, the mauerlat is attached to both supports: higher (front) and lower (back). Mounting is carried out using anchor bolts, studs or metal staples, depending on the material of the walls (brick, gas block, wood).
If the walls are made of porous materials, such as aerated concrete, an armopositor belt is necessarily laid under the mauerlat for a uniform distribution of the load. Without a reinforced belt, the fasteners can loosen under the influence of wind or the weight of snow. Between the wood and the wall is always a layer of waterproofing, usually a ruberoid or bitumen tape.
The timber fastening should be rigid and reliable, since it is he who perceives the bulk of horizontal effort. When using studs, they are laid at the stage of laying walls or pouring concrete. For wooden walls, a screw or forged brackets driven from the end are often used.
Installation and fastening of rafting legs
The rafters are the main bearing element of the roof, so their fastening requires special attention. At the lower end, the truss leg rests on the lower wall mauerlat, and at the upper end, on a high support. To ensure reliability, special fastening elements are used: metal corners, sleds (sliding supports) or logs.
If the span between the walls exceeds 4.5 meters, the rafters must be reinforced with tarmacs or intermediate supports to exclude deflection. Rigid attachment Both ends are allowed only for small buildings, where temperature deformations of wood will not lead to cracking of the nodes. In wooden houses, sliding fasteners are often used to compensate for the shrinkage of the walls.
☑️ Installation of the truss system
The step of installation of rafters is selected in accordance with the cross-section of the board and the planned load. A standard 50x150 mm board allows you to take a step of up to 1 meter, but for heavy coatings it is reduced to 60 cm. All rafters should lie in the same plane, which is checked by a strained thread or laser level.
Crate and counter-crate device
After installation of rafters, a crate is mounted, which serves as the basis for the roofing material. The type of crate (solid or sparse) depends on the type of finishing. For bitumen shingles and roll materials, a solid flooring of OSB boards or plywood is required, and for slate, profnastile or metal tile, a sparse crate of bars or boards is enough.
An important element is counter-crate - bars that are attached along the rafters on top of the waterproofing. They create a ventilation gap necessary to remove moisture from the underroof space. Without proper ventilation, condensate can cause decay of wooden structures and metal corrosion.
| Type of roofing | Crate type | Step (mm) | Materials |
|---|---|---|---|
| Metal tile | Sparse | 350-400 | Board 25-32 mm |
| Fresh-natil | Sparse | 400-500 | Board 25 mm |
| slate | Sparse | 500-550 | Bruss 50x50 mm |
| Bitumen shingles | It's all over. | - | OSB-3/Plywood |
Mounting elements of the crate is made by nails or screws. The length of the fastener should be such as to break through the board of the crate and enter the rafter by at least 25-30 mm. This will ensure the monolithicity of the entire structure.
Waterproofing and wind protection
Laying of waterproofing film is a mandatory step that protects the insulation and wooden structures from moisture. The film rolls horizontally, starting with a cornice overhang, with the overlap of the canvases 10-15 cm. It is important not to confuse the sides of the membrane if a diffusion material is used that allows steam to pass only one way.
⚠️ Warning: Don’t stretch the waterproofing film too much! Between the rafters should remain sagging 1-2 cm to compensate for the temperature expansion and compression of the material.
The joints of the film must be glued with special tape to ensure the tightness of the contour. At the exit points of pipes or ventilation channels, the film is carefully cut and glued to the passage elements. The quality of this stage directly affects the heat-efficiency roofs and no leaks.
Do I need vapor insulation?
Steam insulation is laid on the inside of the insulation (from the room) to protect wool from water vapor coming from the inside of the house. Waterproofing is outside, under the roof.
Roofing fixing
The final stage is the installation of the finishing coating. Sheets of metal roofing or profnatile are fastened in the lower wave by special roofing screws with a rubber washer (EPDM). The screws are twisted strictly perpendicular to the surface to avoid deformation of the metal and violation of tightness.
When installing, it is important to observe the sequence of stacking, usually starting from the bottom row and moving up. The lateral overlap of the sheets should be one wave, and the vertical - 15-20 cm, depending on the angle of inclination. For metal cutting, use metal scissors or jigsaw, but not a Bulgarian, so as not to damage the zinc layer.
Use only galvanized screws with colored polymer coating in the tone of the roof - this will prevent the appearance of rusty flows after 2-3 years.
In places adjacent to the walls, metal slats are installed, which are injected under the roof or into the slab, providing reliable protection from water leakage. All open metal sections are recommended to be treated with anti-corrosion paint.
Frequent errors in installation
One common mistake is saving on fasteners. Using conventional nails instead of screws or the absence of washers can lead to the fact that the roof will be torn off by the first strong wind. Also often forget about ventilation, which leads to rapid rotting of the rafters.
Incorrect calculation of overhangs leads to the fact that water drains directly onto the foundation or walls, causing their destruction. The minimum length of the overhang should be 30-40 cm. In addition, ignoring the treatment of wood with antiseptics reduces the service life of the structure at times.
⚠️ Warning: Never use nails for roofing without rubber washers or sealant - leaks are guaranteed to begin through such holes.
Questions and Answers (FAQ)
What is the minimum angle of inclination for a single-sided roof?
The minimum angle depends on the material: for roll coatings (euroruberoid) allowed 3-5 degrees, for the flooring - from 8 degrees, and for metal roofing and slate recommended at least 14-20 degrees for a confident snowfall.
Do I need to make a ventilation gap under the roof?
Yes, ventilation clearance (ventzor) is mandatory for all types of roofs, except for flat ones operated with floatable waterproofing. It provides air circulation by removing moisture from the insulation and preventing the wood from rotting.
Can you fasten a rafter directly to the wall without a mauerlat?
Mounting the rafters directly to the wall is not recommended, since it is difficult to ensure a uniform distribution of the load. Mauerlat serves as a connecting element that unites the truss system into a single design and transfers weight to the walls.
Which is the best plank to use for rafters?
The optimal choice is a dry trimmed board of conifers (pine, spruce) of the first grade. The standard cross-section for flights up to 4 meters is 50×150 mm or 50×200 mm, depending on the pitch and snow load.