Felt roofing — repair, overlay & full replacement
Three-layer SBS-modified bitumen torch-on felt with mineral cap sheet. Modern felt is nothing like the cheap stuff from the 1970s — properly fitted, it'll outlast its 20-year guarantee comfortably. Right answer for awkward shapes, tight chimney details and roofs we'd rather not strip back to deck.
What we mean by "felt"
"Felt roof" is one of those terms that has changed completely over the last thirty years but kept its old name. When most people picture a felt roof they think of cheap mineral-finish bitumen sheet — the stuff that started cracking the moment it saw a winter and lasted maybe ten years if you were lucky. That product still exists at the bottom of the market and we don't use it.
What we install is SBS-modified bitumen, also called polymer-modified felt. It's a multi-layer system: a vapour control layer, a reinforcing underlay, and a mineral-finished cap sheet — all bonded together with a gas torch. The SBS modifier makes the bitumen stay flexible across the temperature range a UK roof actually sees, so it doesn't crack in February or run in August. Properly installed, it's a 20–25 year roof.
When felt is the right answer
EPDM rubber is our default for most domestic flat roofs because it's slightly cheaper and seam-free. But felt is the better choice in several situations:
- Complex shapes. Multiple changes of plane, awkward upstands, ducts and roof penetrations. Felt is bonded and dressed in pieces; you can detail in around almost anything.
- Tight chimney upstands. Dressing felt into a brick chimney is a cleaner detail than trying to make EPDM behave in the same situation.
- Overlays of existing felt. A failing felt roof in reasonable condition can often be overlaid with a fresh cap sheet rather than stripped — fast, cheap and effective. EPDM overlays of felt are possible but more involved.
- Where foot traffic matters less. Felt can take some foot traffic but isn't as forgiving as GRP — so for balconies we'd usually pick GRP, but for a hidden garage roof felt is fine.
The fitting process
A typical torch-on felt re-roof on a domestic property (garage, kitchen extension, dormer) runs over two to three days:
- Day 1: Strip the existing roof down to deck. Inspect for rot — most decks in Newcastle are 18mm WBP plywood from the original install and need replacement panels in 20% of jobs. Replace as needed. Fit insulation to current Building Regs spec (typically 120mm PIR for a U-value of 0.18). Fit vapour control layer.
- Day 2: Fit underlay sheet, bonded with gas torch. Fit mineral-finished cap sheet, fully bonded with gas torch. Fit edge trims, drip edges, and outlet collars.
- Day 3 (if needed): Re-dress chimney lead apron, complete perimeter detailing, install or replace skylights, final tidy.
Two fitters on site. Scaffold on the eaves for single-storey work; tower scaffold for two-storey. Bulk rubbish skip on the day of the strip.
What brands we use
For SBS torch-on felt: IKO Permatec and Bauder Therma. Both come with manufacturer warranties of 15–20 years on the materials. Both are widely stocked at trade merchants, which matters in 15 years' time when you need a repair patch.
For thermal insulation: Celotex or Kingspan PIR boards. 120mm minimum for current Building Regs compliance on a warm-roof build-up.
Felt vs EPDM — which should you pick?
If you've got a simple rectangular garage or extension roof with no awkward details, no chimney upstand and no foot traffic, EPDM is usually slightly cheaper, slightly faster to fit, and seam-free. If you've got a complex shape with multiple upstands, a chimney, or you're overlaying rather than stripping, felt is usually the better answer.
Repairs to existing felt
The only time we won't patch is if the roof has had three or four previous patches in the same general area — at that point it's a sign of widespread substrate failure and we'd quote for an overlay or replacement.
Other things we install & repair
Leak Diagnosis & Repair
Tracking the leak path properly, then patching it permanently.
Read more →Solar Panel Mounts
Ballasted tilt frames that don't pierce the membrane.
Read more →Skylights & Rooflights
Kerb-mounted Velux, Fakro and Keylite flat-glass rooflights.
Read more →GRP Fibreglass
Hand-laminated, walkable, takes paint or anti-slip aggregate.
Read more →Commercial Roofs
Single-ply for industrial units, schools and retail.
Read more →Concrete Flat Roofs
Refurbishing post-war concrete decks with overlays.
Read more →Get a free written quote — no charge, no obligation
Tell us about your flat roof. We'll arrange a site visit, give you a fixed-price written quote, and explain the options in plain English.