The Problem
The customer had an old, failed felt roof that had lived out its lifespan. Years of exposure to the sun’s UV rays had heavily degraded the felt, allowing water to get in. Felt that has degraded this far cannot be patched for long, and water that gets through eventually rots the deck beneath it.
What We Found
Once the old covering was removed, the roof deck had rotted. A new waterproof covering fitted over a rotten deck will not last, so the deck had to be renewed first. We also found that the old bedded ridges, set in mortar, would stop us forming a correct upstand where the felt meets the ridge line.
Work Carried Out
- Replaced the rotted roof deck with new 18mm OSB boards
- Installed a high-quality three-layer torch-on felt system, built to last
- Removed the old bedded ridges so that a correct upstand could be installed
- Fitted a new, modern ventilated dry-ridge system in their place
A three-layer system, with a base layer, an intermediate layer and a mineral cap sheet bonded together, gives a continuous, durable waterproof surface and is much better than a single thin layer.
The Result
A fully renewed, watertight roof on a sound deck, with a neat ridge detail. The customer was left with a 10-year insurance-backed guarantee.
Is Your Flat or Low-Pitched Roof Failing?
Cracking, blistering and water ingress are signs that felt has reached the end of its life. See our flat roofing page, or request a free survey and quote.
Why Three Layers?
A torch-on felt system built from a base layer, an intermediate layer and a mineral-finished cap sheet, all heat-bonded together, forms a continuous waterproof surface that is far more durable than a single thin layer. The mineral finish also protects the bitumen from UV, which is what destroyed the old roof.
Why Replace the Deck First?
A waterproof covering is only as good as what it sits on. Fitting new felt over a rotten deck would have failed again quickly, so the deck was replaced with new 18mm OSB boards first.
Questions About This Job
How long does a torch-on felt roof last?
A well-installed multi-layer felt roof can give 20 years or more of service, depending on the deck, the drainage and how well it is maintained.
Why was the ridge replaced?
The old bedded ridges had to come off to form a correct upstand where the felt meets the ridge, and a modern ventilated dry-ridge system replaced them.
See our flat roofing service for more.
Planning a Flat Roof Replacement?
Ask for the deck to be checked as part of any quote, because new felt over a damp or rotten deck will not last. We also recommend asking what the build-up is, how many layers are being bonded, and how the upstands and ridge details will be formed. More detail is on our flat roofing page, or request a free survey and quote.
