How to properly cover a garage roof with roofing felt: a step-by-step guide with photos and tips

A garage roof made of roofing felt is a classic solution that has been proven for decades. This material is affordable, easy to install and, if installed correctly, lasts 10–15 years without leaks. However, many garage owners are faced with problems: swelling of the canvas, peeling at the seams, or premature cracking. The reason most often lies not in the quality of the roofing felt, but in a violation of the technology for laying it.

In this article we will analyze the entire process from A to Z: how to choose correct roofing material for your climate, prepare the base (including concrete, wood and metal roofs), lay materials in layers with overlaps and seal seams. We will pay special attention typical mistakes, which reduce the service life of the coating by 2–3 times. For example, why you can’t put roofing felt on a wet base even in dry weather, or how to avoid “waves” on the surface after winter.

The material will be useful for both beginners and those who have already tried to cover a roof on their own, but encountered leaks. We have included unique data on deposition temperature conditions for different brands of roofing felt (RKP-350, RPP-300, Euroroofing felt), which are rarely mentioned in general instructions, but they are critical to the durability of the coating.

1. Which roofing felt to choose for the garage: comparison of brands and their properties

Not all roofing felt is equally good for a garage roof. Main selection criteria: base density, type of impregnation and the presence of protective coating. For example, roofing felt with coarse sprinkles (marked “K”) will last longer in exposed areas, as it protects against UV rays, and “P” (dust-like) is suitable only for lower layers.

Let's consider popular brands and their purpose:

• 📌 RKP-350 — roofing felt with dust-like coating. Optimal for lower layers or temporary covering. Price: ~250 rub/roll (15 m²).
• 🏗️ RPP-300 — lining roofing felt with fine-grained topping. Used as waterproofing layer under the main coating.
• ☀️ RKK-420 - roofing with coarse-grained coating. Best choice for top layer in regions with hot summers (sun protection).
• ❄️ Euroroofing felt (TechnoNIKOL, Bikrost) - a modern analogue with a bitumen-polymer base. Service life up to 20 years, but the price is higher (~800 rubles/roll).

For most garages in central Russia, the optimal combination is: RPP-300 (bottom layer) + RKK-420 (top). If the roof is flat or with a minimal slope (up to 5°), 3–4 layers will be required; for pitched roofs (10–30°), 2 layers are sufficient.

2. Substrate preparation: cleaning, leveling and priming

70% of success depends on the quality of foundation preparation. Even the most expensive roofing material will not save you from leaks if there are cracks, dust or moisture underneath it. Let's consider three types of bases and their preparation:

Base type	Required work	Materials/tools
Concrete slab	Remove old paint, fill cracks with cement mortar, and treat with primer.	Spatula, cement, roller, bitumen primer.
Wooden sheathing	Impregnate with antiseptic, level with plywood or OSB, sand down any uneven areas.	Antiseptic, 10 mm plywood, sander.
Metal sheet	Clean from rust, degrease, coat with anti-corrosion primer.	Metal brush, solvent, primer Hammerite.

General rule for all types: the base must be dry. You can check the humidity in a simple way: place a piece of polyethylene measuring 1x1 m on the roof and press it along the edges. If after 4–6 hours condensation appears under the film, the roof must be dried with a hair dryer or the work must be moved to a sunny day.

⚠️ Attention: If the garage was built less than a year ago, the concrete slab can retain residual moisture for up to 6 months. In this case use vapor barrier membrane (for example, Yutafol) before laying roofing felt.

3. Technology for laying roofing felt: step-by-step instructions

Before starting work, check the weather: the air temperature should be not lower than +5°C (for built-up roofing felt - not lower than +15°C). Winds over 5 m/s will complicate the process, especially in high garages. Prepare your tools:

• 🔥 Gas burner (for built-up roofing material) or bitumen mastic (for stick-on).
• 📏 Roulette, knife for cutting roofing material, roller for rolling.
• 👷 Gloves, respirator (when working with a burner).
• 🧲 Magnetic holder for the burner (so as not to burn the roof).

Laying algorithm:

1. Rolling out the roll. Unfold the roofing material on the roof so that it lies across the slope (for pitched roofs) or with an overlap of 10–15 cm (for flat ones). Cut off the excess, leaving a margin of 10–15 cm at the edges for bending.
2. Heating the base. For built-up roofing felt, heat the base with a burner until the bitumen appears shiny. For stick-on, apply mastic with a roller in a layer of 1–2 mm.
3. Gluing. Gradually roll out the roll, pressing it with a roller. Make sure that no bubbles form - they should be pierced and pressed immediately.
4. Applying the second layer. Repeat the process, shifting the roll so that the seams of the bottom and top layers do not match (overlap of at least 8–10 cm).

Check the weather (no rain, wind up to 5 m/s)

Clear the roof of debris and dust

Prepare tools (torch, knife, roller)

Mark the rolls taking into account overlaps

Wear protective equipment (gloves, goggles) -->

For flat roofs it is recommended to lay roofing felt "envelope": first layer along, second across. This prevents water from accumulating in the seams. On pitched roofs, start installation with bottom edge, moving upward so that the top sheets overlap the bottom ones.

4. Sealing seams and finishing edges: how to avoid leaks

The most vulnerable place of a roofing felt roof is the seams and edges. Even with proper installation, gaps may appear here over time. To seal, use:

• 🔥 Bitumen mastic (cold or hot). Apply with a brush to joints 5–7 cm wide. Suitable for small garages.
• 🛠️ Self-adhesive tapes (for example, Nicoband). Convenient for vertical joints (adjacent to the wall).
• 🧲 Metal aprons. Installed on the edges of the roof and secured with self-tapping screws rubber gaskets.

Pay special attention corners and junctions with walls. Here's what's recommended:

1. Cut from roofing felt additional "aprons" 30x30 cm in size and stick them in an overlapping corner on the wall.
2. Coat the corner with bitumen mastic in 2–3 layers.
3. Place a metal corner (galvanized) on top and secure with dowels.

⚠️ Attention: If the garage roof borders the living spaces (for example, the garage is built into the house), use elastic sealants based on polyurethane (for example, Soudal Fix All). They do not crack due to seasonal deformation, unlike bitumen mastics.

5. Common mistakes and how to avoid them

Even experienced craftsmen sometimes make mistakes that shorten the service life of a roofing felt roof. Here are the most common:

Error	Consequences	How to avoid
Laying on a wet base	Peeling of roofing material, bubbles, leaks after 1–2 years.	Check moisture with film (see section 2).
Overlap less than 8 cm	Seams coming apart due to temperature changes.	Make an overlap of 10–15 cm, glue with mastic.
Using one layer	The service life is reduced to 3–5 years.	Minimum 2 layers, for flat roofs - 3-4.
Lack of ventilation	Accumulation of condensation under roofing felt, rotting of the wooden sheathing.	Install ventilation fungi (1 piece per 20 m²).

Another common problem is "waves" on roofing feltthat appear after winter. The reason lies in improper storage of rolls before laying (they cannot be held vertically) or in the absence expansion gaps between the sheets. To avoid this, leave a gap of 1-2 cm between the edges of the roofing material, which will close when heated in summer.

6. Caring for a roofing felt roof: how to extend its service life

A roofing felt roof requires minimal but regular maintenance. Basic procedures:

• 🧹 Clearing debris. Leaves, branches and dust retain moisture, accelerating the breakdown of the material. Clean your roof 2 times a year (spring and fall).
• 🎨 Renewing the protective layer. Recoat your roof every 3-4 years bitumen varnish (for example, Bitumen Varnish TechnoNIKOL). This will restore elasticity and protect against UV rays.
• ❄️ Snow removal. A thick layer of snow (more than 30 cm) can deform the roofing material. Clean it off with a plastic shovel without damaging the surface.
• 🛠️ Repair of minor damage. Cracks up to 5 cm can be repaired bitumen patch, large ones - only by replacing a section of roofing felt.

For regions with sharp temperature changes (for example, Siberia), it is recommended to check every 5 years vapor barrier integrity. Over time, it may lose its properties, and condensation will begin to accumulate under the roofing felt. In this case, you will have to remove the top layer and lay a new membrane.

What to do if roofing felt drips?

If wet spots appear on the roof, follow the algorithm:

1. Find the location of the leak (most often these are seams or connections to the wall).

2. Clean the area from dirt and dry with a hairdryer.

3. Apply to the damaged area bitumen mastic in 2 layers with a fiberglass lining.

4. If the damage is large (more than 20 cm), cut out this area and apply a patch of new roofing felt with an overlap of 15 cm.

7. Alternatives to roofing felt: when to choose a different material

Ruberoid is not the only option for a garage roof. In some cases, it is more appropriate to use other materials:

• 🏗️ Profiled sheeting. Suitable for pitched roofs (slope from 10°). The service life is 20–30 years, but requires lathing and sound insulation.
• 🧱 Ondulin. Lightweight and easy to install, but fades in the sun and lasts 10–12 years.
• 💎 Membrane roofing (PVC, TPO). Expensive (from RUB 1,500/m²), but service life is 50+ years. Optimal for flat roofs.
• 🌿 Green roof. Suitable for eco-garages, but requires enhanced waterproofing and drainage.

Ruberoid remains the best choice if:

• The budget is limited (the cost of coverage is from 150 rubles/m²).
• The roof is flat or with a minimal slope.
• The garage is not heated (there is no risk of condensation from inside).

Frequently Asked Questions

Is it possible to put roofing felt on old roofing felt?

Yes, but only if the old coating has not swollen or crumbled. Before laying a new layer:

1. Clear the roof of debris and moss.
2. Coat the old coating with bitumen mastic for better adhesion.
3. Lay the new roofing material perpendicular to the old one so that the seams do not coincide.

If the old roofing felt has bubbles or cracks wider than 2 cm, it must be completely removed.

What is the minimum roof slope for roofing felt?

Minimum slope - 2° (about 3.5 cm per 1 meter length). For flat roofs (slope 0–2°) you need:

• Laying at least 3-4 layers of roofing material.
• Usage reinforcing fiberglass between layers.
• Organization internal drain (for example, funnels in the center of the roof).

How to cut roofing felt so that the edges do not crumble?

Use sharp roofing knife with a trapezoidal blade (for example, Olfa L-1). Before cutting:

1. Mark the cutting line with chalk or marker.
2. Place a board under the roofing felt to avoid damaging the bottom layer.
3. Cut at once, avoiding tears.

For curly cuts (for example, around a pipe), use metal scissors.

How long does it take for roofing felt to dry after installation?

Drying time depends on the type of roofing felt and weather:

• Stick-on roofing felt (on mastic) - 12–24 hours at +20°C.
• Welded roofing felt — cools down in 1–2 hours, but complete polymerization of bitumen takes 3–5 days.

In rainy weather, drying time increases by 2–3 times. Do not walk on the roof for the first 2 days after installation!

Is it possible to paint roofing felt for sun protection?

Yes, but not all colors are suitable. Use:

• Acrylic paint for bitumen surfaces (for example, Dachbeschichtung from Alpina).
• Bitumen varnish (transparent or colored).
• Rubber paint (for example, Super Decor).

Do not use oil or alkyd paints - they will crack after a year. Before painting, clean the roof from dust and prime it.