Old roofing felt on the roof of the garage is a headache for most car owners. Over time, it cracks, swells and begins to leak water, threatening not only your car, but also the foundation of the building. Complete replacement of the roofing pie is an expensive and time-consuming solution, but there is an alternative: re-roof over existing roofing felt modern materials. This approach will save up to 40% of your budget and time if done correctly.

In this article we will look at 7 proven materials for covering a garage roof using old roofing felt - from budget (bitumen mastic + roll coatings) to premium (membrane systems). You will learn:

  • 🔹 What materials are compatible? with old roofing felt without dismantling
  • 🔹 Step by step instructions for each option (with photos and video links)
  • 🔹 Common mistakes, due to which a new roof leaks within a year
  • 🔹 Price comparison and service life (table with calculations for 2026)

Important: not all materials are equally good for flat and pitched roofs. We will separately consider the nuances for each type of garage.

1. Is it possible to lay new material on top of the old roofing felt?

Yes, but with reservations. Old roofing felt can serve as the basis for a new coating if:

  • 🔸 He does not peel off from the base (concrete, wooden sheathing)
  • 🔸 On it no deep cracks (up to 5 mm are acceptable)
  • 🔸Absent swelling and rot (especially important for wooden garages)
  • 🔸 Roof slope does not exceed 15° (for rolled materials)

⚠️ Attention: If roofing material "walks around" underfoot or falls through - dismantling is required! In such cases, even the most expensive membrane will not save you from leaks.

📊 What type of roof does your garage have?
Flat (slope up to 5°)
Sloping (5–15°)
Gable (15°+)
I don't know

Before laying new material necessarily:

  1. Clean the roof of debris, moss and dust (use a stiff brush or high-pressure washer).
  2. Dry the surface with a hair dryer or in sunny weather (humidity no more than 5%).
  3. Seal cracks with bitumen mastic or sealant Soudal Bitifix.
  4. Prime the surface with a primer (for example, TechnoNIKOL No. 01) for better adhesion.
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To check the moisture content of roofing material, apply a plastic film measuring 1x1 m to it for a day. If condensation appears under the film, continue to dry the roof!

2. TOP 7 roofing materials: comparison of pros and cons

The choice of material depends on the budget, climate and type of roof. Below is a rating of solutions from the most budget to the premium.

Material Service life Price per m² (2026) Pros Cons
Bitumen mastic + reinforcing fiberglass 5–7 years from 200 ₽ ✅ Cheapest of all
✅ Easy installation		 ❌ Requires updating every 2–3 years
❌ Does not withstand severe frosts
New roofing felt (grades RKP-350, RKK-420) 8–12 years from 250 ₽ ✅ Time-tested
✅ Good waterproofing		 ❌ Heavy (load on the structure)
❌ Flammable
Gidroizol (surfaced) 10–15 years from 350 ₽ ✅ UV resistant
✅ Doesn't rot		 ❌ Requires a gas burner
❌ Difficult to style alone
Soft tiles (bitumen) 15–20 years from 500 ₽ ✅ Aesthetic appearance
✅ Easy to repair		 ❌ Only for pitched roofs (slope from 12°)
❌ Dear sheathing
PVC membrane 25–30 years from 800 ₽ ✅ Absolutely waterproof
✅ Chemical resistance		 ❌ High price
❌ Requires professional installation

Critical point: For garages in regions with sudden temperature changes (Siberia, Far East) are optimal PVC membranes or hydroisol — they do not crack in frosts below −30°C. In the southern regions (Krasnodar Territory, Crimea), even budget mastic is suitable, but with mandatory fiberglass reinforcement.

3. Bitumen mastic: the cheapest method (step by step)

Ideal for flat roofs with a slope of up to 5°. Mastic creates a seamless coating that “seals” all the cracks of the old roofing material.

Remove loose roofing material with a spatula | Treat the surface with a primer TechnoNIKOL No. 04|Apply mastic in 2 layers with fiberglass reinforcement|Roll with a roller to remove bubbles-->

Materials:

  • 🔹 Bitumen mastic (for example, Bitumast or Gidroizol MGH-3) - 20 kg per 10 m²
  • 🔹 Fiberglass with a density of 100–150 g/m²
  • 🔹 Bitumen primer - 1 l per 5 m²
  • 🔹 Roller and brush for application

Instructions:

  1. Apply primer to cleaned roofing felt and let dry (1-2 hours).
  2. Roll out the fiberglass fabric over the roof, leaving an overlap of 10 cm.
  3. Apply the first layer of mastic (1–2 mm thick) and insert the fiberglass into it.
  4. After 4–6 hours, apply a second layer of mastic perpendicular to the first.
  5. For additional protection, sprinkle the top layer with quartz sand (5 kg per 10 m²).

⚠️ Attention: Carry out work at temperatures from +5°C to +30°C. At −5°C the mastic will become brittle, and at +35°C it will become too liquid and will drain from the roof.

What to do if the mastic bubbles?

Bubbles appear due to moisture under the roofing material or uneven application. Solution:

1. Puncture the bubbles with a needle and squeeze out the air.

2. Fill the holes with mastic using a syringe.

3. For large defects (5 cm or more), cut off the bubble, dry the base with a hairdryer and apply a patch.

4. Fused materials: waterproofing and new generation roofing felt

Weldable coatings (for example, Technoelast, Uniflex) is more reliable than mastic, but requires a gas burner. Suitable for roofs with a slope of up to 15°.

Benefits:

  • 🔹 Service life up to 15 years (with proper installation)
  • 🔹 Resistance to mechanical damage
  • 🔹 Possibility of laying in 1–2 layers (depending on climate)

Step-by-step installation:

  1. Unwind the roll 50–60 cm and heat the underside and base with a burner.
  2. Glue the material by rolling it with a roller from the center to the edges.
  3. Lay the next roll with an overlap of 8–10 cm, heating the joints.
  4. For the second layer, move the rolls so that the seams do not match.

⚠️ Attention: Do not overheat the material - bitumen may ignite! Optimal distance of the burner from the surface: 15–20 cm. Use propane-butane mixture (a 27 liter cylinder is enough for 30–40 m²).

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Fused materials are the best balance of price and quality for garages in central Russia. They can withstand from −40°C to +90°C without loss of properties.

5. Soft tiles: aesthetics + durability

If your garage has a roof pitch of 12° or more, soft tiles (e.g. Shinglas, Katepal) will become a stylish and durable solution. However, this option requires continuous sheathing on top of the old roofing felt.

What you will need:

  • 🔹 OSB-3 sheets or FSF plywood (thickness 12–18 mm)
  • 🔹 Underlay carpet (for example, Anderep Ultrafelt)
  • 🔹 Soft tile shingles (consumption: 3–4 m² per 1 m² of roof)
  • 🔹 Roofing nails with a wide head

Stages of work:

  1. Mount the sheathing on top of the roofing felt, securing it with self-tapping screws to the supporting beams.
  2. Lay the underlayment with a 10 cm overlap, gluing the joints with bitumen mastic.
  3. Start installing shingles from the bottom up, offset each row by 1/2 to 1/3 the length of the shingles.
  4. Secure with nails (4 pieces per shingle) and coat the joints with mastic K-36.

⚠️ Attention: Soft tiles not suitable for flat roof garages — on slopes less than 12°, water will stagnate, which will lead to rotting of the sheathing.

6. PVC membranes: premium protection for 30 years

Membranes (eg Logicroof, PVC Planter) is the most reliable, but also the most expensive solution. They don't rot, don't light up and can withstand loads of up to 300 kg/m² (relevant for snowy regions).

Installation features:

  • 🔹 The membrane can be laid mechanical fastening (self-tapping screws with thermal washers) or ballast method (load with gravel).
  • 🔹 The joints are welded with hot air (temperature 400–600°C).
  • 🔹 For garages, a membrane with a thickness of 1.2 mm is sufficient.

⚠️ Attention: PVC membranes not compatible with bituminous materials! If there are traces of mastic on the old roof, they must be completely removed with a solvent. White spirit.

7. Common mistakes and how to avoid them

Even high-quality materials leak if the installation technology is violated. Here 5 most common mistakes:

  1. Ignoring ventilation. Without gaps between layers of materials, condensation will destroy the roof in 2-3 years. Solution: use counterbattens 2–3 cm thick for air circulation.
  2. Saving on overlaps. The minimum overlap for rolled materials is 8 cm (for membranes - 5 cm). With a lower value, the joints will separate at the first frost.
  3. Work in rain or fog. Moisture underneath the material will cause swelling. Check the weather 3 days before installation.
  4. Using cheap mastics. Solvent-based mastics (for example, Bitumast) are cheaper, but last 2 times less than polymer-bitumen ones (for example, TechnoNIKOL No. 24).
  5. Lack of parapet protection. The edges of the roof must be raised onto vertical surfaces by at least 15 cm and secured with metal strips.
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To check the quality of membrane welding, use tensile test: Try to separate the welded edges with your hands. If the seam does not come apart, the seal is ensured.

FAQ: Frequently asked questions about covering a garage roof

Is it possible to lay corrugated sheets on top of roofing felt?

Yes, but only if:

  • 🔸 Roof slope from 8° (otherwise water will flow in).
  • 🔸 You will edit sheathing in increments of 30–40 cm for ventilation.
  • 🔸 Use corrugated sheeting with a wave height of at least 20 mm (for example, S-21 or NS-35).

⚠️ Without sheathing, condensation will accumulate under the corrugated sheeting, and the roofing material will rot in 3-5 years.

How many layers of roofing felt are needed for a garage?

Minimum - 2 layers:

  • 🔸 Bottom: lining roofing felt (brand RPP-300).
  • 🔸 Top: roofing with stone topping (RKK-420).

In northern regions it is recommended 3 layers (optional - glass insulation).

How to seal the joints between roofing felt and the wall?

Use:

  • 🔸 Bitumen sealant (for example, Soudal Bitifix) + serpyanka (fiberglass tape).
  • 🔸 Metal apron (galvanized steel) for parapet.
  • 🔸 Liquid rubber (for example, Elastopaz) for complex shapes.

⚠️ Apply sealant with a pistol at an angle of 45° for a better fit.

What is the most durable material for a garage?

The leaders in terms of service life are:

  1. 🥇 PVC membrane - 25–30 years.
  2. 🥈 Soft tiles — 15–20 years.
  3. 🥉 Built-up hydroisol — 10–15 years.

Budget options (mastic, roofing felt) will last 5–10 years with proper care (snow removal, crack repair).

Is it necessary to insulate the garage roof when covering it?

Insulation is recommended if:

  • 🔸 The garage is heated (even periodically).
  • 🔸 You store in it cold-sensitive equipment (batteries, paints).
  • 🔸 The roof freezes in winter (ice, icicles).

Optimal insulation:

  • 🔹 Extruded polystyrene foam (for example, Penoplex) - for flat roofs.
  • 🔹 Mineral wool (density 140 kg/m³) - for pitched ones.

⚠️ Install insulation between the sheathing, and not on top of roofing felt!