When an old felt roof fails, many people ask whether the new covering can go straight over the top. The answer is sometimes, but often it is better to strip the old layers first.
When overlaying can work
If the existing felt is dry, firmly attached and the deck beneath is sound, it may be possible to lay a new covering over it, with a suitable separating layer so the adhesive does not attack the old material. This saves time and avoids disposal costs, and keeps the existing build-up as it is.
When stripping is better
If the old felt is wet, blistered, loose or sagging, the new covering will not stick well, and trapped moisture can cause further damage. A deck that has gone soft or rotten needs to be exposed and repaired, and this can only happen if the old covering is taken off. Multiple old layers of felt can also be heavy and uneven, which would show through the new membrane.
What a roofer checks
The roofer looks at the surface, taps and probes for soft spots, checks whether the roof has insulation and how it is detailed, and decides what is best. A moisture check can help where there is a worry about a wet deck.
Edges and details
Either way, the edges, upstands and outlets need proper attention. Old flashings and trims often need replacing, and a simple overlay does not deal with poor details.
Honest advice
We would rather tell you when stripping is needed than lay a new roof over a problem. A roof that is going to last is built on a sound base.
See our EPDM Rubber Roofing section or call 07766 547309 for a free quotation.
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