Q&A – Torch down repair

A Californian homeowner recently reached out with some question about their 15-year-old roof.

Looking at the roof of their shed, Rod noticed a leak. They asked the AskARoofer experts this:

I have a torch down roof on a low slope shed roof that is about 15 years old. I found some rot in a fascia board, indicating a leak. The leak appears to be on the edge of the roof where it meets the metal drip edge. I would like to know if I can heat the torch down roof material and roll it back about a foot along this edge, replace the fascia board and then re heat the torch down? Would I need an adhesive between the metal and the roofing material? If so, what would work best? Thank you.

We recieved multiple responses from our experts, including this one from Jana Zavala of HER Roofing:

Torch down roofs are done in layers. However, most torch down roofs that I have seen on residential homes are made up with a base sheet and a cap sheet. If your torch down roof is only a base and cap, then you are looking at a roof replacement, not a repair. That is because the life expectancy is about 10 years. The surface will look like it's alligator skin texture - rough and possibly cracking.

I would not recommend heating torch down unless you are a professional roofing contractor that has the insurance, appropriate fire extinguisher and can perform a fire watch. In addition, reheating an old torch down, especially one that has aged out, doesn't work.

Our other response came from roofing expert John Kenney with Cotney Consulting Group:

Rod, I wouldn’t recommend using a torch on an older structure, especially one with a wood deck and fascia board. The fire risk increases significantly due to the dry, aged materials and potential hidden gaps near the edge. Instead of reheating and rolling back the old membrane, which may not re-bond reliably, it’s safer to carefully cut back the material, perform the fascia repair and then patch using a cold-applied modified bitumen system or self-adhering membrane. If you must seal it to metal, use a compatible adhesive or flashing cement rated for metal-to-membrane applications. You’ll preserve roof integrity without putting the structure at risk.

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