Car owners often face the problem of leaks in garages, especially if the building has been in use for several years. The most affordable and time-tested solution for flat or low-slope roofs is the use of bitumen roll materials. A properly installed garage roof covering with roofing felt can last up to 15 years, reliably protecting the car from precipitation and dampness.
This material is valued for its availability, ease of installation and excellent waterproofing properties. However, like any construction work, the installation process requires adherence to technology and an understanding of the physics of the processes occurring in a multi-layer roofing pie. In this article we will analyze all stages of work, from the selection of materials to the final sealing of the seams.
Choosing the right roofing material for a garage roof
The first step will be the correct selection of material, since the durability of the roofing cake directly depends on this. There are many modifications on the modern market, and it is important not to get confused by the markings. The basis of the classic roofing felt is roofing cardboard impregnated with bitumen, but for a garage it is better to consider more modern options, for example, euroruberoid or glass insulation.
When choosing, pay attention to the type of coating that protects the bitumen layer from ultraviolet radiation and mechanical damage. Coarse pavement (stone chips) is usually applied to the outer face layer, creating a reliable shield from the sun. Fine-grained or dusty coating is more common on lower layers or on materials intended for internal waterproofing.
For a garage roof, the optimal choice would be a material marked RKP (roofing felt with dust-like coating) for the lower layers and RKK (coarse-grained) for the topcoat.
The technical characteristics of the base also play a role: fiberglass or polyester is much stronger than ordinary cardboard and less susceptible to rotting. If you plan to make a roof that will last forever, you should pay extra for a synthetic-based material that will not lose elasticity under sudden temperature changes.
Required tools and surface preparation
High-quality preparation of the base is 80% of the success of the entire operation. Before starting work, it is necessary to thoroughly clean the roof of old covering, debris, dust and vegetation. If there are swellings or detachments of old bitumen on the surface, they must be removed mechanically using a spatula or hatchet.
To work you will need the following set of tools:
- 🔥 Gas burner with a cylinder for fusing material
- 🧹 Hard broom and industrial vacuum cleaner for cleaning
- 🪣 Primer (bitumen mastic) and brush or roller for priming
- 🔪 Roofing knife for cutting sheets
- 👞 Special shoes with soft soles or felt pads
After cleaning, the surface must be dried. A damp base is absolutely not suitable for installation, as water will turn into steam when heated and tear off the coating. To check the humidity, you can stick a small piece of polyethylene with tape around the perimeter and leave it overnight: the absence of condensation indicates readiness for work.
☑️ Checking the readiness of the base
Laying technology: hot and cold methods
There are two main installation methods: fusing (hot method) and gluing to mastic (cold method). Welding is most common for garages with concrete slabs. In this case, the bottom layer of material is heated by a burner until the bitumen melts, after which the roll is rolled out and pressed tightly to the base.
The cold method involves the use of bitumen mastics, which are applied to the base and the lower part of the canvas. This method is less fire hazardous, but requires more drying time and is often inferior in adhesion reliability at sub-zero temperatures. Recommended for beginners fusing method, since it allows you to visually control the quality of heating.
⚠️ Attention: When working with open fire, follow safety precautions. Make sure there are no flammable objects nearby and keep a fire extinguisher or a container of sand handy.
An important point is to control the heating temperature. An underheated material will not stick, but an overheated one will lose its properties and become brittle. An indicator of proper heating is the appearance of a characteristic shine and slight “floating” of the bitumen layer.
The nuances of working with a burner
Hold the torch at a 45 degree angle, heating both the base and edge of the roll at the same time. The movements should be smooth, in the shape of the letter “L”, in order to evenly melt the bitumen. Do not hold the flame in one place for too long to avoid burning the base.
Step-by-step instructions for installing roofing felt
The styling process begins with preparing the primer. This is a liquid bitumen solution that is applied to a cleaned base to improve adhesion and dust removal. After the primer has dried (usually 2-4 hours), you can begin laying out the first layer.
Installation is carried out from the bottom up if the roof has a slope, or from the far corner to the exit on a flat roof. The canvases are laid with an overlap: the side is 10-15 cm, the end is at least 15 cm. In places of overlap, the old material must be melted and carefully rolled with a heavy roller to remove air.
Procedure:1. Warming up the edge of the roll and the base.
2. Rolling out the canvas with simultaneous heating.
3. Rolling with a roller from the center to the edges.
4. Check the seams and, if necessary, reheat.
The number of layers depends on the roof slope and climatic conditions. For flat roofs (slope up to 5 degrees), it is recommended to lay at least three layers: two underlying ones and one finishing layer with a protective coating. For pitched roofs (slope 5-15 degrees), two layers are sufficient.
The quality of the roof is determined by the tightness of the seams: it is through them that moisture most often penetrates, so pay maximum attention to the overlaps.
Calculation of quantities of materials and consumption table
To avoid a situation where there is not enough material in the midst of work, it is necessary to make an accurate calculation in advance. The roof area is multiplied by the number of layers, and 10-15% is added to the resulting value for overlaps and trims. Primer consumption is also taken into account, which depends on the porosity of the base.
Below is a table of approximate material consumption for different types of work:
| Type of work | Primer consumption (l/m²) | Number of layers | Overlap (%) |
|---|---|---|---|
| Repair (1 layer) | 0.3 - 0.5 | 1 | 10-15 |
| New roof (flat) | 0.4 - 0.6 | 3 | 15-20 |
| New roof (pitched) | 0.3 - 0.5 | 2 | 10-15 |
| Sealing seams | - | 1 (local) | - |
When purchasing rolls, pay attention to their area. A standard 1 meter wide roll will usually contain 10 or 15 square meters of material, but the actual usable area will be less due to overlaps. Euroroofing material often sold in 10 m² rolls.
Sealing of junctions and complex assemblies
The most vulnerable places of any roof are the junctions with walls, ventilation pipes and gutters. This requires a special approach and the use of additional materials. To seal vertical surfaces, abutment strips or additional strips of roofing material are used, rising onto the wall to a height of 20-30 cm.
The material around pipes and other communications is thoroughly scalded. The "stocking" method is often used, when a piece of material with a hole is put on the pipe and melted to the base. All joints are additionally coated with bitumen mastic to prevent capillary suction of moisture.
⚠️ Attention: Do not leave the vertical edges of the roofing material on the walls open. They must be pressed down with a metal strip or a galvanized apron and sealed, otherwise water will flow under the coating.
Pay special attention to drainage funnels. Additional layers of insulation are laid around them, forming a kind of bowl that directs water directly into the drain. Usage bitumen-polymer mastics in these nodes significantly increases the reliability of the connection of dissimilar materials.
Frequent errors and coating service life
Even if the technology is followed, mistakes can be made that will shorten the service life of the roof. One of the most common is laying on a damp base or in rainy weather. Moisture trapped under a layer of bitumen will sooner or later lead to swelling and ruptures.
Another mistake is saving on the number of layers. An attempt to make a roof in one layer where there are two or three will lead to rapid failure of the coating under the influence of ultraviolet radiation and temperature deformations. Also, do not ignore cleaning the roof from snow in winter, as ice masses can damage the protective coating.
With proper operation and high-quality installation, the service life of a roofing felt roofing is:
- 📅 Classic roofing felt: 5-7 years
- 📅 Improved roofing felt (glass base): 10-12 years
- 📅 Euroroofing felt with polymer additives: 15-20 years
Regular inspection of the roof (in spring and autumn) will allow you to timely identify minor defects and eliminate them with local repairs, without waiting for a large-scale leak.
Is it possible to put roofing felt on an old coating?
Technically, this is possible if the old coating is firmly in place and has no swelling or moisture. However, experts recommend removing old layers to see the condition of the base and avoid trapping moisture between layers, which will lead to rot.
At what temperature can roofing felt be laid?
The optimal ambient temperature for work is from +5°C to +25°C. At lower temperatures, the material becomes brittle and bitumen does not melt well. Winter work requires the use of special frost-resistant mastics and heating of the material in a warm room.
What is the difference between roofing felt and euroroofing felt?
The main difference is in the base and composition of bitumen. Classic roofing felt is made on cardboard and simple bitumen; it is less elastic. Euroroofing material has a base made of fiberglass or polyester and contains polymer additives (SBS, APP), which makes it more durable and resistant to temperature changes.
Is it necessary to sprinkle roofing felt with sand?
If you are using a material without a protective coating (for example, lining) as a top layer, then yes, while the bitumen is hot, it needs to be sprinkled with coarse sand or crumbs. This will protect soft bitumen from sticking in summer and mechanical damage.