A properly designed do-it-yourself carport made of metal can withstand a snow load of up to 200 kg per square meter, if a profile with a wall thickness of at least 3 mm is used during installation and the geometry of the trusses is observed. An error in choosing the section of the rack or saving on the foundation often leads to deformation of the structure after the first winter, when heavy wet snow falls on a gentle slope. It is the calculation of the load-bearing capacity and rigidity of the nodes that becomes the critical factor determining the durability of the entire building, and not just the decorative cladding of the roof.
⚠️ Attention: The use of a profile pipe with a thin wall (less than 2 mm) for main racks with a height of more than 2.5 meters without additional stiffeners is strictly not recommended, as this creates a risk of collapse in strong winds.
Before purchasing materials, it is necessary to clearly determine the dimensions of the future parking space, taking into account not only the length and width of the body, but also the necessary margin for comfortable opening of the doors. The standard width of one parking space is 3 meters, but for a full-fledged shed, where it is possible to store equipment or install additional supports, this parameter is often increased to 3.5–4 meters. The height of the span should ensure unobstructed passage even for cars with high ground clearance or an installed roof rack, so the minimum vertical clearance is taken to be 2.3–2.5 meters.
Selection of materials and design calculations
The basis of longevity is the right choice rolled metal, which will absorb all static and dynamic loads. For racks, a square pipe with a cross section of 100x100 mm or 80x80 mm is most often used, as it provides maximum resistance to bending in two planes. The rafter system can be made of a pipe of a smaller diameter, for example 60x40 mm or 50x50 mm, which allows reducing the overall weight of the structure without loss of strength if the pitch of the trusses is calculated correctly.
A critically important parameter when choosing a metal is the thickness of the pipe wall: for load-bearing elements it should not be less than 3-4 mm, otherwise the welds may burn through the profile during installation, weakening the assembly. For the lathing on which the roofing material is directly attached, a 40x20 mm or 20x20 mm pipe, laid in increments of 60-80 cm, depending on the rigidity of the selected coating, is optimal.When calculating the amount of materials, it is necessary to take into account technological allowances for welding and trimming, which usually amount to 10-15% of the total volume. It is also worth deciding in advance on the type of connection of the elements: welded joints provide solidity, but require qualifications, while bolted joints allow the structure to be disassembled if necessary, although they are inferior in rigidity.
Preparing the foundation and installing racks
Installation of support pillars begins with marking the territory and digging holes or drilling holes to a depth below the freezing point of the soil, which in the middle zone is about 1.2–1.5 meters. Neglecting this requirement and installing the racks to a depth of 50-70 cm will result in the forces of frost heaving pushing the supports out of the ground, warping the entire frame and compromising the integrity of the roof. As a base for the racks, concreting in a well or installing ready-made concrete cups is used, which guarantees the immobility of the structure.
☑️ Foundation preparation checklist
After installing the pipes in the holes, it is necessary to strictly control their verticality using a building level or plumb line, fixing the position with temporary spacers until the concrete hardens. The concrete mixture should be prepared with the addition of crushed stone of a fraction of 20-40 mm to increase strength, and it is advisable to cover the upper part of the heads with metal plates to protect against moisture getting inside the pipe cavity.
Frame assembly and welding work
Installation of the top trim and trusses requires precision, since any distortions at this stage are difficult to correct without dismantling the structures. Trusses are assembled on the ground in the form of ready-made triangular or trapezoidal modules, which simplifies welding work and allows you to check the geometry before lifting to a height. Welding is performed with a seam along the perimeter of the junction, avoiding spot tacks, which are not able to withstand wind loads and can burst due to thermal expansion of the metal.
| Design element | Profile type (mm) | Installation pitch (m) | Connection type |
|---|---|---|---|
| Support posts | 100x100x4 | 3.0 | Welding/Concreting |
| Bottom harness | 80x80x3 | 3.0 | Butt welding |
| Roof trusses | 60x40x3 | 1.5 - 2.0 | Welding with gussets |
| Lathing | 40x20x2 | 0.6 - 0.8 | Screws/Welding |
During the welding process, it is important to follow the sequence of seams in order to minimize thermal deformations of the metal, which can “drive” the entire structure. Experienced craftsmen recommend first making tacks in the corners, then checking the diagonals and only after that welding the joints with a continuous seam, knocking off the slag after each pass of the electrode.
Welding safety
When performing welding work at height, it is necessary to use a safety belt and a reliable platform. Sparks from welding can cause dry materials to ignite, so the work area must be cleared of flammable items.
Roofing installation
The choice of roofing material directly affects the requirements for the sheathing and the overall weight of the canopy, so this stage is approached taking into account the load-bearing capacity of the assembled frame. Polycarbonate is a popular option due to its lightness and ability to transmit light, but it requires a special thermal gap during installation and the use of thermal washers to compensate for expansion. Corrugated sheets or metal tiles are heavier and noisier when it rains, but they are highly durable and durable with proper anti-corrosion coating.
The sheets are fastened through a wave into the lower part of the profile to avoid leaks, with the obligatory use of rubber sealing washers. When working with polycarbonate, it is important not to overtighten the screws, as this can lead to cracking of the material around the hole, and also to maintain the orientation of the sheets relative to the UV protective layer, which is usually marked on the protective film.
Helpful advice: To drain water from a flat or flat roof of a canopy, install gutters and downpipes, otherwise the flowing stream will quickly wash away the soil around the racks and damage the blind area or covering of the site.
Protecting metal from corrosion
A metal canopy is constantly exposed to aggressive environmental influences, so high-quality anti-corrosion treatment is a mandatory step, and not a recommendation. Before painting, all welds are sanded smooth with a grinding machine, rust and scale are removed, after which the surface is degreased with a solvent to improve primer adhesion.
The primer is selected taking into account the type of metal and operating conditions; compositions with a rust converter are often used, which make it possible to neutralize foci of corrosion without mechanical stripping to bare metal. The final coating is applied in two layers with intermediate drying, with special attention paid to hard-to-reach places and internal cavities of pipes, which can be protected with special aerosol compounds before welding.
Additional equipment and electrification
A modern carport is often equipped with additional systems that increase operating comfort, such as lighting, video surveillance or automatic gates. Electrical cables are laid in corrugated pipes or metal hoses attached to frame structures, with the mandatory use of circuit breakers and RCDs to prevent fires.
Main conclusion: The reliability of a canopy depends not so much on the thickness of the metal, but on the quality of the foundation and the correct geometry of the trusses, so saving on the design or depth of concreting is unacceptable.
When planning electrification, it is worth providing an outlet for connecting an electric vehicle charger or a car washing tool, as well as motion sensors to automatically turn on the lights. All electrical installation work must be carried out in compliance with the rules of the PUE, with grounding of the metal frame, which in the event of an insulation breakdown may be energized.
⚠️ Attention: When installing electrical wiring on a metal frame, use only double insulation of cables and be sure to ground the entire structure to prevent electric shock.
How to calculate the roof slope angle for a canopy?
The angle of the roof depends on the type of roofing material and the amount of rainfall in the region. For polycarbonate, the minimum angle is 5-10 degrees, for corrugated sheeting - 8-12 degrees, and for metal tiles - at least 14 degrees. In snowy regions, the angle is increased to 20-30 degrees for better snow melting.
Is it necessary to make a concrete platform under a canopy?
A concrete or asphalt deck under a canopy is desirable as it prevents dirt and mud from forming after rain. If the budget is limited, you can use a fill of medium-fraction crushed stone with geotextiles or lay paving slabs, which will ensure drainage and cleanliness.
What truss pitch is optimal for a 6-meter canopy?
For a span of 6 meters, the optimal truss pitch is 1.5–2 meters. Increasing the pitch will require strengthening the cross-section of the purlins and trusses, which will lead to excessive consumption of metal, and reducing the pitch is not practical from an economic point of view and will make the structure heavier.
What is the best way to paint a metal canopy?
For painting metal canopies, alkyd or acrylic enamels for exterior use, as well as specialized hammer paints that hide minor surface defects, are best suited. It is important to use a 3-in-1 enamel primer, which combines a rust converter, a primer and a topcoat.