Modern roofing systems are increasingly moving away from classic wooden solutions, paying attention to more durable and stable materials. Roof crate made of metal profile becomes the quality standard for objects with increased responsibility, since steel is not subject to rotting, does not deform from moisture and withstands significant loads without loss of geometry. This is especially true for complex roofing structures where the accuracy of each millimeter is important.
The choice in favor of metal is dictated not only by the desire to extend the life of the building, but also by the need to minimize operating costs. Wooden timber, even treated with antiseptics, eventually shrinks, cracks and can become a haven for insects. Profile tube or U-shaped They are devoid of these drawbacks, providing the perfect plane for laying the finishing surface for decades.
In this article, we will discuss in detail the process of creating a load-bearing frame made of metal. You will learn about the types of profiles, the methods of attaching them to the truss system and the nuances that beginners often miss. A properly assembled frame is a guarantee that your roof will withstand any snowfall and gust of wind.
Advantages and Disadvantages of Metal Crate
The main argument for is the absolute non-combustibility of the material. Unlike wood, steel crates do not support combustion, which is critical for the safety of the entire structure. Besides, metallic It has a high load-bearing capacity with less own weight, which allows for wider spans between supports.
However, metal has its own characteristics that must be considered during the design phase. The main enemy of steel is corrosion. Despite the galvanized coating, the places of cutting and drilling require mandatory protection with special compositions. Ignoring this rule can lead to rust, which will eventually destroy the structure.
⚠️ Attention! When cutting the profile with a Bulgarian abrasive circle, a strong heating of the metal occurs, which destroys the zinc layer. Use only metal scissors or a saber saw to preserve anti-corrosion properties.
Another advantage is the stability of the size. Metal does not "lead" when changing humidity, as it happens with wood. This means that the fasteners of the roofing will not experience unnecessary stresses on tearing or compression. Step crate will remain unchanged throughout the lifetime of the service.
Material selection: profile pipe or P-profile
To create a high-quality base under the roof, two types of rolled metal are most often used: a square or rectangular pipe, as well as a special bent profile. The choice depends on the type of roofing and the pitch of the truss system. For lightweight coatings, such as false roofing or flooring, often used U-shaped galvanized steel.
The profile pipe, as a rule, has cross-sectional dimensions from 20x40 mm to 40x60 mm and a wall with a thickness of 1.5-2 mm. It provides high stiffness and is ideal for heavy types of shingles or heavy snow loads. It is important to choose a material with factory galvanizing to ensure the durability of the structure without additional painting.
Bending profiles created specifically for the roof have a number of advantages over tubular analogues. They are lighter, often have already ready-made holes for fasteners and special bends for fast fixation. The use of such elements significantly speeds up installation and reduces labor costs.
Calculation of metal thickness
For spans between rafters up to 1 meter, a wall thickness of 1.5 mm is sufficient. If the rafters pitch is more than 1.2 meters or you plan to walk on the roof during maintenance, choose a profile with a wall of 2 mm or more.
Essential tools and supplies
The quality of installation depends on the tool used. Working with metal will require a reliable screwdriver with high torque and a set of bits for screws. A conventional drill will not work here, as it will not provide the necessary effort to screw the fastener into the metal.
For cutting the profile, metal scissors (manual or electric) or a saber saw will be indispensable. As already mentioned, the use of UCM (Bulgar) with cut-off circles on the metal is extremely undesirable due to the burning of zinc. You will also need a roulette, marker and level to control the plane.
Special stains are used as a fixture. metal-handling with a press puck or a six-sided hat. It is important that they are galvanized and have a rubber pad (EPDM) if the cap is outside or in the area of possible contact with water. Brackets or clamps may be required to connect the profile with rafters.
- 🔧 Screwdriver battery (minimum 18V) and spare battery.
- ✂️ Metal scissors for right and left cut or saber saw.
- 📏 Roulette construction (5-10 meters) and marking cord.
- 🧤 Protective gloves (metal has sharp edges) and glasses.
Installation technology: step-by-step instructions
Installation begins with a check of the geometry of the truss system. All the legs should be in the same plane. If there are deviations, they must be eliminated before the start of fastening the crate, otherwise the roof will go "wave". The first step is to lay waterproofing film on top of the rafters with the mandatory sagging between them for condensate drain.
Then the first element is mounted - the cornice bar or the starting profile. It must be installed strictly parallel to the cornice and fixed to each rafter. The accuracy of the installation of the first row depends on the smoothness of the entire roof, so you can not rush here. Use a tight lace to control the line.
☑️ Checking before mounting the crate
Then, intermediate profiles with a calculated step are attached. Fixing is carried out through the body of the profile or in special grooves, if a specialized system is used. The screws are twisted perpendicular to the surface to avoid distortion. After installing each 3-4 row, it is recommended to check the diagonals and the general plane.
In places of adjoining, end and around chimneys, the step of the crate is usually made continuous or reduced. This is necessary for reliable fastening of the finishing elements and preventing deflections of the roofing under the weight of snow or man. A more powerful profile or paired elements can be used here.
Calculation of the step of the crate under different coatings
The crate step is the distance between the profile centers. It depends on the type of roofing material and the angle of slope. For metal roofing, the pitch is strictly tied to the length of the coating module (wave) so that screws fall into the crest of the wave and into the center of the crate profile.
For the flooring step can be arbitrary, but it is usually from 50 to 100 cm, depending on the bearing capacity of the sheet. Finger roofing requires a solid base or very frequent step to prevent the metal from clapping in the wind. Errors in calculations can lead to deformation of the roof.
Below is a table with indicative step values for various materials:
| Type of roofing | Recommended step (mm) | Profile type | Note |
|---|---|---|---|
| Metal tile | 300 - 400 | P-profile 40x20x1.5 | Depends on the length of the module |
| Profnastic flooring (C8-C21) | 500 - 1000 | Pipe 40x20x2 | Depends on the thickness of the sheet. |
| False roofing | Solid / 300 | U-profile enhanced | Requires a hard base |
| Ondulin/Schifer | 450 - 600 | Pipe 40x40x2 | 3 bars per sheet |
Accurate compliance with the step of the crate under the metal roof is critically important: an error of even 2-3 cm will lead to the fact that screws will fall past the wave, violating the tightness of the roof.
Fixing and adjoining points
Fixation of the metal profile to wooden rafters is carried out using screws on wood with a wide hat or through special brackets. If the rafters are also metal, metal screws or bolt joints are used. In places of docking profiles along the length, it is necessary to do a cover of at least 10-15 cm.
Particular attention should be paid to the nodes of the communication passage and adjoining the walls. Here the crate should be reinforced with additional elements. Metal has a high coefficient of thermal conductivity, so in places of contact with other materials (for example, with a brick pipe), it is recommended to use thermal fracturing gaskets or sealants.
All sections of the profile obtained during installation must be treated with an anti-corrosion composition (for example, zinc-containing paint or primer). This will restore the protective layer and prevent the formation of rust foci that can spread further along the profile.
⚠️ Attention! When working at height with a metal profile, be especially careful. Metal is slippery, especially after dew or rain. Use safety belts and shoes with non-slip soles.
Frequently Asked Questions (FAQ)
Can I cook a metal crate?
Welding is possible, but not recommended for a galvanized profile, as the high temperature destroys the zinc coating in and around the seam area. The welded seam will have to be thoroughly cleaned and covered with several layers of anticorrosion paint. It is better to use mechanical fastening (bolts, screws, rivets).
Do I need to treat a metal profile with an antiseptic?
No, the metal does not rot and is not affected by fungus, so treatment with bioprotective compounds, as in the case of wood, is not required. The main task is to protect against corrosion. If the profile is galvanized, additional processing is needed only for the cutting sites.
Which profile is better: square tube or P-shaped?
The U-shaped profile is lighter and cheaper, easier to mount, but less resistant to twisting. The square tube is stronger and stiffer, but heavier and more expensive. For a private house with a conventional roof, a high-quality P-profile 1.5-2 mm thick is often enough.
How to connect a profile if you do not have enough length?
Docking is done by the fly. The minimum length of the overhang should be 150-200 mm (or 3-4 wave profile, if it is corrugated). The connection is fixed by screws on both sides of the joint. It is important that the joint falls on the truss leg for support.