What Is Tourch-Down Roofing?

Choosing the right kind of roof for a building project is important for practical reasons, not just aesthetics.


Many times the building style determines the type of roof--a cedar shake roof would not look right on a Mediterranean villa. If the roof of a building is flat or has a shallow slope, the choice of roofing material takes extra significance since there is a greater possibility that water will pool on the roof.

Torch down roofing is a roofing product that is designed for flat or low angle roof. It gets its name from the method of application. The side of the material that will be in contact with the sheathing underneath is melted with a torch to seal the material down to create a waterproof seal.


A properly installed torch down roofing system will last a long time. If it is done as a two-layer system with one base layer and one torch down layer, the roof will last 15 years. Three-layer systems with a base, a smooth torch down layer and a torch down layer with a granular surface can last 20 years or more.

Previous Roof Removal

If the new torch down roof will be installed on an existing structure, the old roof may not need to be removed. If the old roofing material is smooth and fairly stable, the base sheet can be nailed directly over the old roofing material. If doing so would create an uneven surface, then the old roofing material should be replaced.

Maintenance and Repair

Torch down roofing systems need little maintenance. Its blend of asphalt and synthetic rubber polymers makes it flexible so it can withstand expansion and contraction due to temperature changes. If the roof does need repairs, they can be made without torches by using adhesive-backed bitumen sheets.

Weather Resistance

Torch down roofing systems are weather resistant by design. The under layer is nailed to the plywood sheeting and then the bitumen sheets are torched to the under layer. Torching the bitumen down seals the layers, and the seams are staggered so there is no direct path for water through the roofing materials.


Torch down roofing systems can be more expensive initially but, due to their weather resistance and long lifespan, that high initial cost pays for itself over time. There are cheaper substitutions available, especially in the under layer but they are not worth it since they will shorten the lifespan of the roof.

About the Author

Steve Montgomery has a wide range of experience and education. He has experience in banking, sales and home improvement in addition to various hospitality related positions. He started writing professionally in 2007 for newegg.com. He holds a Bachelor of Science in hotel and restaurant management from Cal Poly Pomona and an Associates of Arts in computer information systems from Pasadena City College.