Modified Bitumen Roofing: Is It Right for Your Flat Roof?
Modified bitumen is a tough, layered asphalt roof for low slopes. It costs $4 to $7.50 per square foot installed. Here is how it compares with TPO, EPDM and tar and gravel.
The basics
What modified bitumen roofing is
Modified bitumen is asphalt modified with rubber or plastic for flexibility, sold in rolls and built up in layers on low-slope roofs. It is the modern descendant of tar-and-gravel built-up roofing.
HomeGuide describes it as flexible and UV resistant. It can be torched down with heat, which carries fire risk, but many brands now make self-adhesive rolls that go on cold.
Good for: roofs that see foot traffic, such as decks over living space or roofs with equipment, because the multi-layer sheet is tough. It also ties in well to shingle roofs at the transition.
Watch for: torch-applied systems need a crew trained for hot work; ask whether they will use torch, hot-mopped or self-adhered. The dark surface absorbs heat unless you choose a granulated or coated cap sheet.
Lifespan: 10 to 20 years on HomeGuide’s figures, so it trails PVC and built-up roofs. Compare every option in our best flat roof material guide.
Questions
Modified bitumen roofing questions
How much does modified bitumen roofing cost?
$4.00 to $7.50 per square foot installed, or $4,900 to $14,600 for a typical roof, per HomeGuide.
How long does a modified bitumen roof last?
10 to 20 years on average, per HomeGuide.
Is torch-down the same as modified bitumen?
Torch-down is one way of installing modified bitumen, using heat to bond the layers. Self-adhesive and hot-mopped versions also exist.
Is modified bitumen better than TPO?
It is tougher underfoot and ties into shingles well. TPO is lighter colored and reflects heat. On cost they overlap.
Can modified bitumen be repaired?
Yes. Blisters, split seams and flashing failures can usually be patched with compatible material.
We get on the roof, photograph what is actually there, and hand you a written report with a price. No charge, and no obligation to book the work with us. If the roof has years left in it, that is what the report will say.
