Bituminous roofing felt

What is roofing felt and what is it used for?

It is the most popular building material for damp-proofing and waterproofing parts of buildings and structures, including foundations, floors, basement walls and roof coverings. It is made by impregnating a carrier of cardboard, glass fibre fleece or polyester fleece with bitumen or tar.

Typical membranes have three layers:

• a carrier that provides tear resistance and dimensional stability,
• a bituminous coating that ensures watertightness and flexibility,
• a surface dressing that prevents the layers from sticking together in the roll and improves durability.

The following types are available on the Polish market:

• traditional, with a carrier made from cardboard or organic fibre fabric, impregnated with bitumen on both sides. They are not particularly durable, but are relatively inexpensive;
• new-generation – with a layered structure. The carrier is made from glass fibre, polyester fabric or embossed film, coated on both sides with bituminous compound. Additives such as APP plastomer and SBS elastomer increase flexibility and resistance to sunlight and make joining the strips easier.

Types:
Depending on their function, roofing felts can be divided into:

• cap sheets – the top layer, with a slate, basalt or ceramic surface dressing that protects against sunlight and temperature effects,
• underlays – with a quartz sand dressing, forming the lower layer in roof coverings, waterproofing and damp-proofing,
• insulating membranes – with talc, used in the lower layers of roof coverings and for waterproofing, damp-proofing and vapour control.

By fixing method, the types are:

• torch-on – for use in multilayer systems or on their own, on roofs with a maximum pitch of 11 degrees,
• bonded with bituminous adhesive (cold or hot) – with a cardboard or glass fleece carrier, used in multilayer roof coverings,
• mechanically fixed – with screws and large washers; they can be fitted directly to the substrate or laid over mineral wool or expanded polystyrene.

What should you look for when buying?

When choosing bituminous roofing felt, consider its thickness, the type and mass per unit area of the carrier, the installation method and the type of bitumen. Our specialists can, of course, help you make your choice.

You also need to consider the type of roof. A pitched roof requires different waterproofing from a flat roof, where the substrate also matters: timber or wood-based material, concrete, or thermal insulation. A green (inverted) roof has different requirements again. Our experts can explain the details, answer your questions and help you choose the right product.

Your choice depends on both your needs and your budget. For example:

• for temporary roof protection, a felt with a cardboard or glass fleece carrier bonded with bituminous adhesive is suitable;
• for refurbishing an old building, choose modified torch-on or mechanically fixed products that do not require maintenance;
• oxidised torch-on products are cheaper;

if speed and reliability are your priorities, choose mechanically fixed SBS-modified products for single-layer roof coverings.

Primers

If a roof is flat and develops blisters or networks of cracks, new felt must be laid. Installing a new covering rarely requires the old one to be removed: with suitable preparation, it can serve as a base. Before laying the new layer, level out all blisters, cracks and depressions in the old covering. Prime the roof with special bituminous products. We recommend using products from the same manufacturer.

Various products are used to prime the substrate and bond the felt:

• solutions,
• compounds,
• bituminous adhesives,
• emulsions.

Manufacturers

Our insulation range includes products from leading companies:

• Icopal
• Swisspor

All the products we offer come with a long-term warranty. Our specialists will be happy to help you choose the right insulation materials. Simply arrange a meeting with an expert from Ambit, who can answer your questions and provide further explanations. This will help you make the best decision and choose the products that best meet your needs.

Types of roofing felt

By function:

• cap sheets,
• underlays,
• insulating membranes

By fixing method:

• torch-on,
• bonded with bituminous adhesive,
• mechanically fixed.