A metal garage is a practical solution for protecting your car, but its roof requires regular maintenance. The main problem with such structures is seams and joints, which over time begin to leak water, rust and collapse. If you ignore cracks, the consequences will be more expensive: from leaks to corrosion of load-bearing elements. In this article we will look at how to cover seams on the roof of a metal garageso that the result lasts for years, not months.
The choice of material depends on several factors: type of metal (galvanized, corrugated sheet, ferrous metal), seam width, climatic conditions and budget. For example, for wide joints it is suitable bitumen mastic with reinforcing tape, and for small cracks - polyurethane sealant. We analyzed 7 popular solutions, compared them in terms of durability and price, and also collected unique life hacks from professional roofersthat save time and money.
Why seams on the garage roof start to leak: 4 main reasons
Before you choose, how to seal seams on a garage roof, it is important to understand why they are destroyed. Most often, it is not the vagaries of the weather that are to blame, but installation or operating errors.
- 🔧 Incorrect roof assembly: if metal sheets are laid with a violation of overlap (less than 10–15 cm) or without sealing gaskets, water will leak out even with minimal precipitation.
- 🌡️ Temperature changes: Metal expands when heated and contracts when cold. If the seam is rigidly fixed (for example, by welding), it will crack over time.
- ⚡ Corrosion: on ferrous metal without a protective coating, rust eats away at the joints in 2-3 seasons. Galvanization lasts longer, but it does not last forever.
- 🐦 Mechanical damage: falling branches, hailstones or careless snow removal with a crowbar leave microcracks that expand over time.
The seams where the roof meets walls, ventilation pipes or antennas are especially vulnerable. Moisture accumulates here, and in winter ice plugs form, which literally break the seal. Professional roofers recommend treat such areas two-component compositions (for example, polyurethane+bitumen), which withstand deformation without loss of properties.
TOP 7 materials for sealing seams: comparison by price and durability
The market offers dozens of solutions for sealing seams, but not all of them are equally effective. We have selected the 7 most reliable options, taking into account the price/quality ratio and reviews from experts. The table below shows the key characteristics of each material.
| Material | Service life | Price per unit | Pros | Cons |
|---|---|---|---|---|
| Bitumen mastic (cold application) | 5–7 years | 200–400 ₽/kg | Versatile, easy to apply, suitable for wide seams | Cracks in the cold, is afraid of UV rays |
| Polyurethane sealant (for example, Soudal) | 10–15 years | 500–800 RUR/tube | Elastic, withstands vibrations, not afraid of temperature changes | Expensive, requires surface preparation |
| Silicone sealant (neutral) | 7–10 years | 300–600 ₽/tube | Waterproof, UV resistant, suitable for small cracks | Does not paint, does not adhere well to bitumen |
| Butyl rubber tape (for example, Nicoband) | 8–12 years | 150–300 ₽/p.m. | Self-adhesive, quick to install, no drying required | Not suitable for joints wider than 5mm |
| Liquid rubber (for example, Elastopaz) | 10–20 years | 1,000–1,500 RUR/kg | Seamless coating, withstands extreme loads | Expensive, requires special equipment |
For most garages, the optimal solution would be combination of bitumen mastic and reinforcing tape. For example, first the seam is coated with mastic, then glued butyl rubber tape, and another layer of mastic is applied on top. This “pie” lasts up to 10 years and is cheaper than liquid rubber. If your budget is limited, you can get by with just mastic, but you will have to renew it every 3-4 years.
Before purchasing a sealant, check its compatibility with metal! For example, acid silicones corrode galvanizing, and acrylic compositions cannot withstand constant humidity.
Step-by-step instructions: how to cover the seams on the roof of a garage with your own hands
The sealing technology depends on the selected material, but the general preparation steps are the same for all cases. Neglecting at least one point reduces the service life of the repair by 2-3 times.
Clean the seams with a wire brush to remove rust and old sealant|
Degrease the surface with a solvent (for example, White spirit)|
Prime the metal with an anti-corrosion compound (for example, Zinkor)|
Dry the roof with a hair dryer or wait for sunny weather |
Cover adjacent areas with masking tape for neatness-->
After preparation, proceed to the main work. Let's look at the process using an example bitumen mastic with reinforcing tape - the most popular option:
Applying the first layer of mastic. Use a brush or putty knife to fill the joint to a depth of 2-3 mm. The mastic should protrude slightly above the surface.
Laying reinforcing tape. While the mastic has not hardened, glue butyl rubber or fiberglass tape, pressing it tightly against the seam. For wide joints (more than 10 mm) use
metal mesh.Final coating. Apply a second layer of mastic over the tape, covering 2-3 cm on each side. This will create a "hydrophobic lip" that sheds water.
If you work with polyurethane sealant, use spray foam gun. Apply the compound at an angle of 45°, filling the joint evenly. After drying (after 24 hours), the excess is cut off with a knife. For liquid rubber You will need an airless sprayer - applying it yourself is ineffective.
What to do if the seam is too wide (more than 2 cm)?
For wide joints, first lay polyethylene foam sealing cord (for example, Vilipes), then fill the remaining space with sealant. This prevents sagging of the composition and saves material.
Errors that reduce seal life by 5 times
Even high-quality materials will not save you if you violate the technology. Here 5 critical errors, which admit 80% of beginners:
- 🚫 Working on a wet surface. Bitumen mastic and sealants do not adhere to wet metal. If the roof is not dry after rain, use construction hair dryer.
- 🚫 Ignoring primer. On ferrous metal without an anti-corrosion layer, the sealant will peel off within a season. Primer (eg GF-021) increases adhesion by 3 times.
- 🚫 Savings on processing width. The sealant is applied only to the seam, without covering adjacent areas. Correct: process a strip 5–7 cm wide.
- 🚫 Operating at temperatures below +5°C. Most sealants lose their elasticity when cold. Exception - winter mastics (for example, TechnoNIKOL No. 21).
- 🚫 No reinforcement. Without tape or mesh, the mastic cracks when the metal is deformed. Reinforcement increases tensile strength by 5 times.
⚠️ Attention: Do not use polyurethane foam for sealing seams on the roof! It absorbs moisture, breaks down under UV rays and lasts no more than a year. Foam is only suitable for temporary repairs.
Another common problem is incompatibility of materials. For example, if the roof already has a layer bitumen mastic, and you apply on top of it silicone sealant, the clutch will be weak. In such cases, the old layer must be completely removed scraper or solvent.
Which sealant to choose for different types of metal
Not all sealants work equally well on galvanized sheets, corrugated sheets or ferrous metals. Here are recommendations for each case:
| Metal type | Recommended sealant | What to Avoid |
|---|---|---|
| Galvanized Sheet | Polyurethane sealant (for example, Soudal Fix All), liquid rubber | Acid silicones, acrylic compounds |
| Corrugated sheeting with polymer coating | Butyl rubber tape, MS polymer sealant (for example, Tytan Professional) | Bitumen mastics (may damage the coating) |
| Ferrous metal (uncoated) | Bitumen mastic + reinforcing tape, epoxy compounds | Silicones without primer |
For corrugated sheets with color coating (for example, Grand Line or Metrotile) it is important to choose a sealant that will not damage the polymer layer. The best option is MS polymers (modified silicones). They do not contain solvents and do not cause paint peeling.
If the garage roof is made of ferrous metal without protection, be sure to treat it before sealing zinc-rich primer (for example, Tsinkol). This will prevent rusting under the sealant layer and extend the life of the repair by 3-5 years.
For galvanized and coated corrugated sheets, use sealants based on MS polymers or polyurethane — they do not contain aggressive solvents and do not damage the protective layer.
Seasonal nuances: when is the best time to repair a garage roof?
The time of year directly affects the quality of sealing. Ideal working conditions:
- 🌤️ Air temperature: +10°C to +25°C. At +5°C and below, most sealants lose their elasticity.
- 🌡️ Humidity: not higher than 60%. In damp weather, mastics do not adhere well to metal.
- ☀️ Solar activity: Cloudy weather is preferable to direct sun, which dries the sealant too quickly, causing cracks.
The best time for renovation is late spring or early autumn. In summer, the metal heats up to +50–60°C, which speeds up the drying of the mastic and can lead to bubbles. In winter, most sealants cannot be used (exception: winter mastics with application temperatures down to −10°C, e.g. TechnoNIKOL No. 24).
⚠️ Attention: If the garage roof northern (little sun), the sealant will take 2 times longer to dry. In this case, use compounds with curing accelerators (for example, SikaBond).
If repairs are urgent (for example, after a hail or hurricane) and the weather is not ideal, follow these rules:
- At temperature
+5°C to +10°Cuse polyurethane sealants - they are less sensitive to cold. - If humidity is high, apply sealant to
2 thin layerswith intermediate drying for 2–3 hours. - In hot weather (>+30°C), work in the early morning or evening when the metal cools down.
Alternative methods: when sealant is not suitable
Sometimes the seams on a garage roof are so bad that sealing won't help. In such cases, radical methods are used:
- 🔥 Welding: Suitable for ferrous metal, but requires professional equipment. After welding, the seam must be primed and painted.
- 🛠️ Installation of aprons: metal or plastic linings are mounted over joints (for example, at junctions with pipes).
- 🏗️ Sprayed waterproofing: Liquid rubber or polyurea is applied in a continuous layer, completely sealing the roof. Cost - from 800 ₽/m².
- 📦 Replacing sheets: if the metal is rusted through, it is cheaper to replace the damaged fragment than to patch holes every year.
For corrugated sheets with damaged polymer coating are often used repair tapes with aluminum layer (for example, Alu-Tape). They not only seal the seam, but also restore the protective layer. The cost is from 300 ₽/rm, but they last up to 10 years.
If the garage roof flat (for example, from metal sheets with a minimal slope), the best solution is sprayed waterproofing. It creates a seamless coating that is not afraid of standing water. The downside is the high price and the need for special equipment.
FAQ: Frequently asked questions about sealing seams on a garage roof
Is it possible to seal the seams on a garage roof with regular silicone sealant?
It's possible, but only if it's neutral silicone (without acetic acid). Acidic silicones corrode the metal and shorten the service life of the repair. For the roof it is better to choose polyurethane or MS-polymer sealant - they are more elastic and durable.
How long does it take for bitumen mastic to dry on a garage roof?
Drying time depends on temperature and humidity:
- At +20°C —
24 hours(until sticky), complete polymerization -7 days. - At +5°C - up to
48 hours. - In wet weather - up to
3 days.
Will help speed up the process construction hair dryer, but the mastic should not be overheated (maximum +40°C).
Which sealant is best for seams wider than 1 cm?
For wide seams (from 1 cm) it is optimal to use:
- Bitumen mastic with reinforcing fiberglass tape.
- Polyurethane foam (for example, Soudal PU Foam) followed by protection with mastic.
- Sealing cord (for example, Vilipes) + sealant.
Foam without protection will last no more than a year - it must be covered with mastic or paint.
How to seal the seams on the roof of a garage if they are already rusty?
Algorithm of actions:
- Clean seam
wire brushorgrinder with petal circle. - Process rust converter (for example, Tsinkar).
- Apply primer for metal (for example, GF-021).
- Fill the seam epoxy putty (for example, Novol) or polyurethane sealant.
If the rust is through, it is better to cut out the damaged area and weld a patch.
Can the sealant be painted after it has dried?
Depends on the type of sealant:
- ✅ Polyurethane and MS-polymer sealants are painted with acrylic or alkyd paints.
- ❌ Silicone and bituminous mastics do not paint - they reject paint. For them, use colored sealants (for example, Soudal in RAL shades).
Wait until completely dry before painting (usually 7-14 days).