Truss for a garage from a profile pipe: step-by-step guide with drawings and calculations

Garage owners often face a problem: how to strengthen the roof so that it can withstand snow loads, does not sag and does not require constant repairs? Solution - profile pipe truss, which evenly distributes the weight of the roof, increases structural rigidity and extends the service life of the building. Unlike wooden beams, metal trusses do not rot or burn and last for decades if installed correctly.

But how to calculate the dimensions, choose a profile and weld the truss so that it does not collapse under the first snow? In this article - step-by-step instructions with drawings, calculation of loads for different regions of Russia, list of tools and 5 critical errorsthat beginners admit. And also - ready-made diagrams for garages 3, 4 and 6 meters wide.

If you are planning to build a garage from scratch or strengthen an old roof, a metal truss will save you up to 30% of your budget compared to buying ready-made structures. The main thing is not to make a mistake with the cross-section of the pipe and the angle of inclination of the slopes. For example, for snowy regions (Siberia, the Urals), the minimum roof slope should be 25–30°, and for the southern ones - 10–15° is enough. More on this and other nuances below.

1. Why do you need a farm in the garage: 3 key functions

Many garage owners mistakenly believe that trusses are only needed for large hangars or industrial buildings. In fact, even for a standard 3x6 meter garage, a metal frame solves three critical problems:

• 🏗️ Load distribution: The truss transfers the weight of the roof (snow, wind, sheathing) to the load-bearing walls, preventing the roof from sagging. Without it, the risk of collapse in winter increases 5 times.
• 🔧 Simplified installation: The finished truss weighs 2–3 times less than concrete beams and can be installed manually without a crane.
• 💰 Saving materials: A profile pipe is cheaper than an I-beam or channel, and in terms of strength it is not inferior to them if calculated correctly.

According to GOST 27751-2014, the snow load in central Russia reaches 180 kg/m², and in the Urals - up to 320 kg/m². Wooden beams will not support such a weight, but a metal truss will cope if it is designed correctly. For example, for a 4x6 m garage in the Moscow region, a pipe truss is sufficient 40×40×2 mm, and for Krasnoyarsk it will be required 60×60×3 mm.

⚠️ Attention: If in your region the standard snow load exceeds 240 kg/m², profile pipe trusses 40×40 mm cannot be used - they are deformed. Check the data for your city on the website Rostechnadzor.

2. Types of trusses for the garage: which one to choose?

Structurally, trusses are divided into three types, each of which is suitable for different conditions:

Farm type	Benefits	Disadvantages	Recommendations for use
Triangular	Easy to manufacture, minimal material consumption	Only suitable for roofs with a slope of 30° or more	Ideal for garages in snowy regions (Siberia, Far East)
Polygonal (polygonal)	Distributes load evenly, suitable for flat roofs	More difficult to calculate and weld	Optimal for garages with an attic or exposed roof
Parallel (rectangular)	Easily attached to walls, suitable for wide spans (from 6 m)	Requires additional braces for rigidity	Best choice for extension garages or gable roofs

Optimal for most garages up to 6 meters wide triangular truss - it is easier to manufacture and requires fewer welds. If the span is more than 6 meters or the roof is flat, use polygonal design with additional racks. For example, for a 4x8 m garage, a pipe truss is suitable 50×50×2.5 mm with a strut pitch of 1.5 m.

3. Truss calculation: formulas, loads and pipe cross-section

An error in calculations can lead to roof sagging or truss collapse. To avoid this, follow the algorithm:

1. Define standard snow load for your region (data taken from SNiP 2.01.07-85*). For example, for Moscow it is 180 kg/m², for Yekaterinburg - 240 kg/m².
2. Calculate payload (weight of roof, insulation, sheathing). For corrugated sheeting + insulation this is ~30 kg/m².
3. Define truss step (optimally 1–1.5 m) and span length (distance between walls).
4. Select the pipe cross-section according to the table:

Formula for calculating the minimum pipe cross-section:

S = (q × L²) / (8 × [σ] × W)

where:

- S — pipe cross-sectional area (cm²),

- q — total load (snow + roof, kg/m),

- L — span length (m),

- [σ] — permissible stress for steel (2100 kg/cm²),

- W — moment of resistance of the pipe (depending on the shape of the profile).

To simplify, use a ready-made table:

Span length (m)	Snow load (kg/m²)	Recommended pipe size	Wall thickness (mm)
3–4	up to 180	40×40	2
4–5	180–240	50×50	2.5
5–6	240–320	60×60	3
6+	320+	80×80	3.5

⚠️ Attention: If your garage is planned attic or exploitable roof, increase the pipe cross-section by 20–30%. For example, instead of 50×50 mm take it 60×60 mm.

Determine the snow area using the SNiP map |

Measure the exact span between walls|

Select the type of roof (weight of corrugated sheeting, metal tiles, ondulin) |

Check the load-bearing capacity of the foundation (for heavy trusses) -->

4. Drawings of trusses for garages of different widths

Ready-made diagrams with dimensions will help you avoid manufacturing errors. Below are drawings for the most popular garage dimensions. All dimensions are for pipe trusses 50×50×2.5 mm (suitable for most regions of Russia).

For a garage 3x6 m (gable roof, slope 25°):

• 📏 Length of the truss along the lower belt: 3.2 m (including overhangs).
• 📏 Height at the ridge: 1.2 m.
• 📏 Step of braces: 0.8 m.
• 📏 Number of farms: 5 pcs. (step 1.2 m).

Download the drawing in DWG format: ferma-3x6.dwg

For a garage 4x6 m (single roof, slope 15°):

• 📏 Truss length: 4.5 m.
• 📏 Height: 0.9 m.
• 📏 Braces: every 1 m.
• 📏 Pipe section: 60×60×3 mm (for snowy regions).

For a garage 6x8 m (mansard roof):

• 📏 Use polygonal farm with additional racks.
• 📏 Height in the skate: 2.1 m.
• 📏 Truss pitch: 1 m.
• 📏 Trumpet: 80×80×3.5 mm.

Critical mistake: many craftsmen forget to take into account the weight of the trusses themselves when calculating the load. For a 50x50 mm pipe this is ~12 kg/m - with a truss length of 6 m the additional load will be 72 kg!

How to adapt the drawing to your garage?

If your garage has non-standard dimensions, use the scaling factor:

1. Measure the actual span (L_fact).

2. Divide it by the base size from the drawing (L_base). For example, if L_fact = 5 m and L_base = 4 m, the coefficient K = 1.25.

3. Multiply all dimensions in the drawing by K, except for the pipe section (select it according to the load table).

4. Increase the pipe wall thickness by 0.5 mm to compensate for the increased span.

5. Step-by-step instructions: how to make a farm with your own hands

To make a truss from a profile pipe you will need:

• 🔨 Tools: welding machine (preferably semi-automatic), angle grinder, tape measure, level, clamps.
• 📦 Materials: profile pipe (according to calculations), electrodes ANO-21 or wire SV-08G2S, primer for metal.
• 📝 Drawing with dimensions (see previous section).

Step 1. Marking and cutting pipes

Transfer the dimensions from the drawing to the pipes using marker and tape measure. For cutting use grinder with a metal disc. Important: the cutting angles must be accurate (error no more than 1°), otherwise the truss will be skewed. To check use 90° square.

Step 2: Assembling the truss on the ground

Weld the truss in a horizontal position on a level area. Sequence:

1. Weld the lower chord (truss base).
2. Install vertical posts and secure them with clamps.
3. Weld the braces, starting from the center to the edges.
4. Check the geometry with diagonals (they must be equal).

Step 3. Welding and processing of seams

Use interrupted seam (length 3–4 cm, pitch 5–7 cm) to save material and prevent deformation. After welding:

• Clean the seams sander.
• Cover the farm primer for metal (for example, GF-021).
• Apply 2 layers of paint (preferably hammer — it hides irregularities).

⚠️ Attention: Do not use corroded or dented pipes for the truss - this reduces the strength by 40%. Before welding, check the metal for rust. magnetic flaw detector or visually.

6. Installation of a truss on a garage: fastening and leveling

Installing the farm is the most critical stage. Mistakes here will lead to roof skew or collapse. Follow the algorithm:

Step 1. Preparing the walls

Attach to the top trim of the garage support plates (made of metal 5–6 mm thick) using anchor bolts M12. The fastening step is no more than 1 m. The plates must be strictly horizontal (check hydraulic level).

Step 2. Raising the truss

For garages up to 6 m long, the truss can be lifted manually using winches or lever system from timber. For spans over 6 m you will need truck crane or telescopic lift. Important: lift from both sides at the same time to avoid distortion.

Step 3. Attaching the truss

The trusses are attached to the support plates using:

• 🔩 Boltov M10–M12 (for collapsible structures).
• 🔥 Welding (for major garages).

After installation, check:

• 📏 Horizontal lower belt (tolerance - 5 mm per 1 m).
• 📐 Verticality racks (deviation no more than 10 mm).
• 🔗 Hardness fastenings (the truss should not wobble under a load of 50 kg).

Step 4. Strapping and roofing

After installing all the trusses:

1. Install runs (horizontal beams) from pipe 40×20 mm in increments of 0.5–0.7 m.
2. Secure sheathing (board 25×100 mm or profile sheet).
3. Lay down roofing (corrugated sheeting, metal tiles).

7. 5 mistakes when making trusses (and how to avoid them)

Even experienced craftsmen make mistakes that lead to truss deformation or roof collapse. Here are the most common:

1. Incorrect brace angle
   

   The optimal angle between the braces and the belt is 35–50°. If the angle is less than 30°, the truss will lose its rigidity. Check the corners goniometer before welding.

2. Saving on pipe cross-section
   

   Pipe 40×40 mm Only suitable for garages up to 4 m in snowy regions up to 180 kg/m². For Siberia, take the minimum 60×60×3 mm.

3. No anti-corrosion treatment
   

   An unpainted truss will rust in 3-5 years. Use zinc primer + polyurethane paint for outdoor work.

4. Weak welds
   

   The seam must be continuous (without gaps) and have leg no less than 4 mm. Check the quality of the seam hammer: Light impacts should not leave any dents.

5. Ignoring wind load
   

   In the steppe regions (Rostov region, Krasnodar region) the wind load reaches 38 kg/m². Strengthen your farm additional connections at the ends.

If you're unsure about your welding skills, have your trusses fabricated by a workshop. Cost of one 4×6 m pipe truss 50×50 mm - about 3,000–5,000 rubles (2026), which is cheaper than repairing a collapsed roof.

8. Cost of materials and alternative options

The price of the truss depends on the size of the garage, pipe section and region. Below are the estimated costs for 2026:

Material	Quantity (for garage 4x6 m)	Price per unit (₽)	Total (₽)
Pipe 50×50×2.5 mm (6 m)	12 pcs.	800–1 200	9 600–14 400
Electrodes ANO-21 (1 kg)	2 kg	250–350	500–700
Primer GF-021 (1 l)	2 l	180–250	360–500
Hammer paint (1 l)	2 l	400–600	800–1 200
Anchor bolts M12 (10 pcs.)	20 pcs.	50–80	1 000–1 600

Total: 12,000–18,000 rubles (excluding tools).

Alternative options:

• 🏗️ Wooden trusses: Cheaper by 30%, but require antiseptic treatment and last 10–15 years.
• 🏢 Finished metal trusses: 1.5–2 times more expensive, but with a guarantee and exact dimensions.
• ⚡ LMK (light metal structures): Suitable for large garages (from 8 m), but require a crane for installation.

If your budget is limited, you can save money by buying a pipe at a metal warehouse at wholesale prices (from 5 tons) or using used materials. However, used pipes must be no corrosion and with a wall thickness of at least 2.5 mm.

FAQ: Frequently asked questions about garage trusses

Is it possible to make a truss from a 40x20 mm pipe?

No, pipe 40×20 mm not suitable for load-bearing trusses - it will not withstand snow loads. Minimum section for a garage: 40×40×2 mm (for spans up to 3 m). For spans of 4–6 m use 50×50×2.5 mm or 60×60×3 mm.

How to calculate the number of trusses for a 5x7 m garage?

The pitch of the trusses depends on the load:

• For snow load up to 180 kg/m²: step 1.2–1.5 m (5–6 trusses required).
• For a load of 240+ kg/m²: 1 m step (7 trusses).

Also take into account the weight of the roof: for corrugated sheeting the pitch can be increased to 1.5 m, for ceramic tiles - reduced to 0.8 m.

Is it necessary to insulate the farm?

The farm itself does not require insulation, but if the garage is heated, insulate roofing between runs. Use:

• 🧊 Mineral wool (thickness 100–150 mm).
• 🧊 Expanded polystyrene (50 mm, but always with a vapor barrier).

Don't insulate the farm foam plastic — it supports combustion!

Is it possible to attach a truss to aerated concrete walls?

Yes, but only using chemical anchors (for example, Fischer FIS V or Hilti HIT-HY 70). Ordinary dowels in aerated concrete will not withstand the load. Alternative - fill armored belt along the top of the walls (width 20 cm, height 15 cm) with embedded plates for fastening trusses.

How to check the quality of truss welding?

Check the seams according to 3 criteria:

1. Appearance: No cracks, pores, lack of penetration. The seam is uniform, without sag.
2. Strength: Light blows with a hammer (200–300 g) do not leave any dents.
3. Geometry: After welding, the truss does not move (check the diagonals).

For critical structures (span >6 m) order ultrasonic inspection of seams (cost ~5,000 ₽).