An application technique for modified bitumen roofing membranes where the underside of the roll is heated with a propane torch as it is unrolled. The heat melts the asphalt backing, turning it into a fluid adhesive that bonds the sheet to the substrate or base sheet. This creates a continuous, watertight seam without the need for hot asphalt kettles or cold adhesives.
The specs call for a torch-down cap sheet over a mechanically fastened base.
Watch the bleed out at the seams. A consistent quarter inch of melted bitumen squeezing out tells you the sheet is properly adhered.
Also heard as
- torch-applied
Related terms
Modified bitumen
A roofing membrane made of asphalt mixed with rubber or plastic polymers for flexibility and strength.
Base sheet
The foundational first layer of felt or membrane in a multi-ply roof system.
Cap sheet
The topmost layer of a multi-ply roofing system that protects the underlying membrane from weather and traffic.
Bleed
Staining from fluids or plasticizers that migrate out of a sealant into porous stone or masonry.