Roofing Felt

Roofing felt is a roofing material used to provide an extra layer of protection and waterproofing between the roof timber deck and the final roofing layer, such as tiles or slates. It’s commonly used for flat roofs and has been around for over 100 years.

CHARACTERISTICS

• Composition: Roofing felt is typically made from a mixture of bitumen, fibrous membrane, and sand. Bitumen is a waterproof material derived from coal-tar pitch or asphalt. The felt is either natural or synthetic, with options like wood cellulose, recycled cloth, fibreglass, or polyester.
• Application Techniques:
  • Torch-On Method: In this technique, the felt is heated using a torch, allowing it to bond securely to the roof surface.
  • Cold Applied Method: Cold-applied bituminous adhesive is used to bond the felt to the roof. This method doesn’t involve heat and is suitable for various roof types.
• Lifespan: Roofing felt typically has a lifespan of around 30 years. It’s a solid choice for flat roofs and can also be used on some sloped roofs. Proper installation is crucial for effective waterproofing. Its always best to follow the manufacturer’s guidelines to ensure a thorough application.

When roofing felt serves as the final layer in home and commercial roofs, it plays a crucial role in providing additional protection and waterproofing.

• Waterproofing: Roofing felt acts as a barrier against water infiltration. It prevents moisture from reaching the underlying roof structure, protecting it from rot and damage.
• Underlayment: Before installing the final roofing material (such as shingles or tiles), roofing felt is laid down over the roof deck. It acts as an underlayment, providing an extra layer of defense.

Types of Roofing Felt:

• Asphalt-Saturated Felt: Traditional roofing felt made from organic materials (such as paper or cellulose) saturated with asphalt. It’s commonly used.
• Synthetic Underlayment: Modern alternatives made from synthetic materials (like fibreglass or polyester). They offer better tear resistance and durability.

Roofing felt is typically rolled out in overlapping layers, starting from the eaves and working upward. It’s secured using nails or staples. Proper installation ensures a watertight seal. Remember that roofing felt is just one component of a well-constructed roof system.

The Torch-On Method is a popular technique for installing roofing felt.

Materials:

• Modified Bitumen Rolls: These rolls consist of a base layer (often fiberglass or polyester) coated with modified bitumen (a type of asphalt). The bitumen is modified with rubber or plastic polymers to enhance flexibility, durability, and weather resistance.
• Propane Torch: A handheld propane torch is used to heat the bitumen during installation.

Installation Steps:

• The roof deck must be clean, dry, and free of debris.
• Any existing roofing material is removed.
• The modified bitumen rolls are laid out over the roof surface. They overlap each other to create a continuous barrier.
• A roofing professional uses the propane torch to heat the bitumen. As it softens, the rolls adhere to the roof deck and to each other.
• The overlapping seams are carefully sealed to prevent water infiltration.
• A cap sheet (another layer of modified bitumen) may be added on top for additional protection.

Advantages:

• Torch-on roofing is durable and can withstand extreme temperatures, UV exposure, and foot traffic.
• The heated bitumen forms a watertight seal.
• The material remains flexible even in cold weather.

Safety Considerations: 

• Due to the use of an open flame, torch-on roofing should only be installed by trained professionals.
• Proper safety precautions are essential to prevent accidental fires.

The Cold Applied Method is an effective technique for installing roofing felt.

Materials:

• Cold Adhesive: This specialised adhesive is used to bond the roofing felt to the roof surface.
• Roofing Felt Rolls: These rolls consist of bitumen-saturated material (such as fiberglass or polyester).

Installation Steps:

• Ensure the roof deck is clean and dry.
• Use a mop, squeegee, or brush to apply the cold adhesive to the roof area.
• Once the adhesive becomes tacky (usually within 15 minutes to 1 hour), place the roofing felt into position.

Advantages:

• Unlike torch-on methods, cold application doesn’t involve open flames.
• Cold-applied membranes work well over various existing roof types.
• The process is quicker compared to traditional hot-applied methods