TPO in a nutshell
TPO is a white single-ply membrane rolled out in wide sheets and welded together with hot air at the seams. It's light, reflective and clean-looking. It's typically installed over insulation board, which can be tapered to build slope.
Modified bitumen in a nutshell
Modified bitumen is a thick, rubberized asphalt sheet, often installed in two plies. It's rugged, handles foot traffic, and works well up parapet walls. A light-colored cap sheet or coating helps with heat and UV.
When a membrane makes sense
- The old roof is coming off anyway
- The roof has large, open areas without many odd shapes
- You'd rather not be on a recoat schedule
- Insulation is being added with board underneath
Wind and edges
On exposed hilltops, membranes are fastened and their edges terminated securely so wind can't get under them. Edge metal and parapet terminations get extra attention.
Comparing options? See metal or flat and spray foam.
Questions homeowners ask
Is TPO good for wind?
Yes, when it's properly fastened and the edges are well terminated.
Can modified bitumen go up the parapets?
Yes — that's one of its strengths.
Is a membrane quieter than metal?
On a flat roof, rain noise is rarely an issue with either.