By Charlie the Roofer for Roofline · Published · Checked against the sources listed below
Not always. Roofing felt is a second barrier under the tiles, so torn or brittle felt is not a leak on its own. It needs attention if you see water trails, damp or rotten battens, or felt sagging and rotting at the eaves. Most fixes are local and done from outside, without a full re-roof.
What does the felt under your tiles actually do?
The felt, or underlay, is a backup layer. Your tiles or slates keep the rain out, and the underlay catches wind-driven rain, snow and drips from a cracked tile and carries them down to the gutter. Wienerberger, the tile maker, describes it as a second protective barrier from the elements. It also helps the roof cope with wind, which is why BS 5534, the British Standard for slating and tiling, includes wind uplift resistance for underlays and applies to repairs and re-roofing as well as new roofs.
With sound tiles above it, a torn section can sit there for years without any water reaching the loft. A tear on its own calls for a closer look rather than a new roof.
Why does old felt crumble at the eaves first?
Older underlay is usually bitumen felt, which turns brittle with age, so on many post-war Yorkshire semis and terraces re-covered decades ago it is near the end of its life. Wienerberger says the market moved away from bitumen underlays as the norm well over 20 years ago, and Klober's Permo Forte, one of the first breathable membranes in the UK, arrived in the late 1990s.
The eaves fail first because the lowest strip of felt runs out over the fascia into the gutter, where it sits in daylight. Roofing Superstore notes that UV from the sun degrades uncovered felt over time. Felt that sags between the rafters also lets water pond behind the fascia. From the ground or a bedroom window you may see black, frayed felt hanging into the gutter. From the loft it often looks brittle and torn along the lowest run.
When does torn felt actually need fixing?
It needs fixing when there are signs that water is getting past the tiles, or when the eaves felt has rotted away. With a torch in the loft, look for these signs:
- dark water trails on the felt or down the rafters, or damp patches in the insulation
- battens showing through a tear that look dark, soft or rotten
- daylight through a tear, which usually points to a slipped or broken tile above it
- felt sagging between rafters at the eaves, or hanging in shreds into the gutter
If you find any of these, the tiles above need checking as well. Our guide on how to find a roof leak covers what to look for in the loft. If the felt is torn but dry, with sound battens and no daylight, it can usually be noted and watched.
Can torn felt be repaired, or do you need a new roof?
Most torn felt can be repaired in one area, and a re-roof only makes sense when the felt is failing across the whole roof or the tiles and battens are worn out too. Repairs are done from outside. The felt sits under the battens and tiles, so a roofer lifts a small area of tiles and battens to fit a new piece of felt under the lap above.
For rotten eaves felt, the usual fix is to lift the bottom row or two of tiles, cut out the old felt, fit a rigid plastic eaves support tray that carries water into the gutter, then re-lay the tiles. MyJobQuote puts the average cost at around £450, with typical jobs from £350 to £650 depending on the roof type (figures updated September 2026). Roofing Superstore recommends fitting trays when fascia boards are being replaced, so it pairs well with new fascias.
If the felt is crumbling right up the roof and the tiles are tired too, re-roofing is usually better value than a run of patches. A new roof would normally get a vapour permeable membrane classified for UK wind zones under BS 5534. Our new roof cost guide covers prices, and our re-roofing guide explains when building control is involved.
If you are not sure what you are looking at, send a photo of the felt or the eaves to Roofline on WhatsApp on 07413 797731, or book a free inspection and we will send you photos of what we find.
Send us a photo on WhatsApp and we will tell you what we think it is and whether it needs a visit. Quotes are free and itemised.
Sources
- BSI Knowledge: BS 5534:2014+A2:2018 Slating and tiling for pitched roofs and vertical cladding
- Wienerberger: Specifying underlay
- Roofing Today: Klober marks 25 years of pioneering vapour permeable membrane (4 December 2025)
- Roofing Superstore: Eaves Guard felt support tray
- Marley: Universal Vapour Permeable Roof Underlay
- RICS: Description of the RICS Home Survey Level 2
- MyJobQuote: Replace eaves felt cost (updated 10 September 2026)
General information about roofing in England, checked against the sources above when published. It is not a substitute for advice about your own roof.
