Felt & Membrane Replacement

The waterproof layer you never see — and why old bitumen felt fails whole roofs.

Under every tile and slate lies the underlay — the felt or membrane that catches whatever wind and rain drive past the covering, and carries it safely to the gutter. When people say "the felt has gone", they mean this layer, and its condition quietly decides whether a roof with minor tile faults stays dry or leaks.

Traditional bitumen felt, standard for most of the twentieth century, becomes brittle with age: it tears at the laps, crumbles along the eaves where sun reaches it, and splits under the weight of any water it's asked to hold. You can read its condition from inside the loft — daylight at the eaves, tears between rafters, black fragments on the insulation are all the same message.

The catch is access: the underlay lives beneath the battens, so replacing it wholesale means lifting the covering. That's why membrane replacement is usually the deciding factor in the repair-versus-re-roof question — once the felt needs doing across the roof, you're describing a re-roof, and pretending otherwise wastes money.

Benefits

Why choose Felt & Membrane Replacement

Honest triage — local felt repairs where they genuinely work
Modern breathable membrane cures chronic condensation
Eaves-edge felt replacement without full stripping, where viable
Loft-side inspection and photographic condition report
Straight answer on when felt failure means re-roofing

Features

What's included

Breathable (vapour-permeable) membranes
Eaves felt support trays — the common local fix
Local patch repairs from within the loft where appropriate
Full membrane renewal as part of re-roofing
Ventilation checks alongside membrane work

Typical lifespan

30–50 years (modern membrane)

Repair options

Repair or replace

Genuinely local damage has genuine local fixes: rotted felt at the eaves (the most common failure, because sun reaches it over the gutter) is repaired with rigid felt support trays slipped in under the bottom courses — a modest job that stops gutter-edge drips. A tear or two can sometimes be patched from the loft. But brittle felt across the roof cannot be usefully patched: every repair tears its neighbour, and the honest fix is renewal under a re-roof.

Common questions

Frequently asked

What's the difference between old felt and breathable membrane? +

Bitumen felt is a simple waterproof sheet — it keeps water out but also traps moist air in, which is why older lofts condensate. Breathable membranes block liquid water while letting water vapour escape, keeping the loft drier, and they stay flexible for decades rather than embrittling.

I can see daylight through my roof in the loft — is that the felt? +

Daylight at the eaves or in small spots usually means torn or shrunken felt behind sound tiles — the covering's fine, its safety net isn't. It's not an emergency in dry weather, but it's the roof telling you its margin for error is gone. Worth an inspection before winter, not after.

Can you replace the felt and keep my existing tiles? +

Yes — that's exactly what most re-roofs on sound coverings are: tiles (or slates) lifted, membrane and battens renewed, and the same tiles re-laid, topped up for breakages. You pay for the labour and the new underlay layers, not a new covering.