Modified Bitumen Torch Roofing

Roofing Types

Modified Bitumen Torch Roofing in Los Angeles

Torch down roofing—also known as “torch on roofing”—is one of the most common types of roofing for flat and slightly-sloped roofs. Torch down roofing consists of multiple modified bitumen membranes, applied with a propane torch. This installation process gives torch down roofing a uniquely watertight seal, making it a great choice wherever water damage is a serious concern.

There are two different types of torch down roofing systems: two-layer and three-layer.

A two-layer torch down roof consists of one base sheet and one smooth cap sheet.

A three-layer torch down roof features the same base and cap sheets, as well as an additional cap sheet with a granulated surface.

Two-layer torch down roofing may cost less to install, but it doesn’t last as long and doesn’t offer as many benefits. The granulated cap layer of a three-layer roof adds to the roof’s energy efficiency, fire resistance, curb appeal and durability.

Torch down roofing comes in the form of rolled sheets. Your roofing contractor will unroll each sheet individually during the installation process (two sheets for two-layer, three sheets for three-layer).

Each sheet of torch down roofing material consists of multiple membranes stacked and adhered together. These are the membrane layers of torch down roofing material, from the bottom up:

Layer 1: Thermo-fusible film.
Layer 2: Modified bitumen.
Layer 3: Reinforced polyester.
Layer 4: Modified bitumen.
Layer 5: (For the third layer of a three-layer roof) Granulated mineral surface.

A compound known as modified bitumen makes up the second and fourth membrane layers of each sheet of torch down roofing material. Bitumen is an asphalt compound. It is used in roofing and other construction applications like road construction and repair. Modified bitumen is asphalt bitumen mixed with a plastic or rubber additive. There are two main types of modified bitumen membrane that are used to create torch down roofing material: Atactic Polypropylene (APP) and Styrene Butadiene Styrene (SBS).

• Atactic Polypropylene (APP)

APP is a type of plastic used to produce modified bitumen for torch down roofing. APP modified bitumen membranes are especially flexible. They respond well to both high and low temperatures.

• Styrene Butadiene Styrene (SBS)

SBS is a type of rubber used to create modified bitumen for torch down roofing. SBS modified bitumen membranes are also flexible, and they have a lower melting point than APP membranes. This means that SBS membranes can be used in torch down roofing, as well as self-adhering and cold-processed roofing systems.