Roofing Glossary

Modified Bitumen

Modified bitumen is asphalt roofing souped up with polymer modifiers — APP or SBS — that give it rubber-like flexibility and far better temperature tolerance than old built-up roofing. It comes in rolls, typically installed in two plies, and is a mainstay of residential flat and low-slope roofing.

Installation methods include torch-down (heat-welding with an open flame — effective but a fire risk requiring skilled crews), self-adhered peel-and-stick (safer, increasingly popular), and cold-applied adhesives. The granulated cap sheet top ply provides UV protection and a finished appearance.

Modified bitumen handles foot traffic better than most single-ply membranes, making it a good choice for flat roofs that get walked on — roof decks, access areas, and service paths.

Why It Matters

For residential flat roofs — porches, additions, garages — modified bitumen is often the most practical choice: durable, walkable, and installed by widely available crews. Confirm the installation method and the crew's experience with it.

Questions about your own roof? Request a free estimate or call Nucci Brothers Roofing at (301) 458-1003.