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GUIDE

Roof Felt — What It Does and When It Needs Replacing

📅 Updated 2026-03-01 🕐 6 min read 📍 Salisbury, Wiltshire

Roof felt is the underlay beneath your tiles that provides a secondary weather barrier. Traditional bitumen felt lasts 30–60 years; most 1960s–70s Salisbury roofs are now beyond this. Failed felt usually means a re-roof. Free felt assessment: 0172 223 9611.

The felt underlay beneath your roof tiles does an essential but invisible job. Most homeowners only think about it when it fails — at which point a repair job becomes a re-roof.

What Roof Felt Does

Felt underlay serves three functions: it provides a secondary barrier against wind-driven rain that gets past tile junctions; it prevents debris dropping into the roof space; and it provides a surface for condensation to drain out rather than saturating insulation and timbers.

BS 5534 now requires breathable underlay with adequate ventilation provision — the non-breathable bitumen felt used on 1960s–70s roofs is a known cause of loft condensation damage.

— BS 5534:2014

How Long Felt Lasts

Traditional bitumen felt, standard until the 1990s, has a design life of 30-60 years. Most of Salisbury's 1960s-70s estate housing (Bishopdown, Bemerton Heath, Durrington) is at or beyond this range. Modern breathable membranes carry 50-year guarantees and significantly outperform traditional bitumen felt.

Signs Felt Has Failed

  • Daylight visible through felt from the loft with lights off
  • Felt that is crumbling, brittle or falling away from the batten line
  • Active water dripping from felt during rain rather than running to the eaves
  • Widespread dark staining indicating sustained water penetration

Felt Failure and Re-Roofing

Felt failure across a significant area usually means a full strip and re-roof is required — you cannot replace felt without removing the tiles above it. If a roof is already in the re-roof window for nail sickness reasons, felt failure often confirms replacement over repair as the correct course of action.

Modern Breathable vs Traditional Bitumen Felt

All our re-roofing work uses modern breathable membrane rather than traditional bitumen felt. Breathable membrane allows moisture vapour from the building to escape through the roof, preventing the condensation accumulation that caused significant secondary damage in many 1960s-80s roofs with impermeable bitumen felt.

📞 Felt assessment — Salisbury

Concerned about felt condition? We include felt assessment in every free roof survey across Salisbury and surrounding areas.

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Last reviewed: 21 July 2026 by Salisbury Roofing Experts

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Felt Types Found on Salisbury Properties

Bitumen Felt (Pre-1990s Properties)

Traditional black bitumen felt was the standard underlay on the 1960s, 70s and 80s housing that makes up the majority of Salisbury's estate stock. It is non-breathable, meaning moisture vapour from the living space that rises into the loft cannot pass through it — instead it condenses on the felt's cold underside and drips back into the insulation or onto the ceiling below. On properties where loft insulation has been laid directly on the loft floor with no ventilation provision between felt and insulation, condensation-related problems with the original bitumen felt are now widespread. This is the primary reason we specify breathable membrane on all re-roofing work.

Breathable Membrane (Post-1990s and Re-Roofs)

Modern breathable membrane is the correct specification for all new roofing work in Wiltshire. It allows moisture vapour to pass through from the warm interior to the cold outside while preventing liquid water ingress from above — functioning correctly in both directions. Modern membranes are significantly stronger than bitumen felt, lighter, and carry 50-year manufacturer guarantees. The cost difference over a re-roof is modest and the performance difference over the subsequent 30 years is significant.

Felt and the Insurance Position

Does Insurance Cover Felt Failure?

Gradual felt deterioration from age is not covered by home insurance — it is wear and tear. If bitumen felt on a 1970s roof has reached the end of its service life, that is a maintenance cost. However, if felt failure has been accelerated or caused by a specific insured event — for example, storm damage that displaced tiles and exposed the felt to sustained weather — the insurer may contribute to replacement costs where the felt damage is demonstrably event-related. We provide detailed written assessments distinguishing event-caused damage from background deterioration for insurance purposes.

Frequently Asked Questions

Yes — we cover Salisbury and all surrounding areas across Wiltshire, Hampshire and north Dorset. Free survey, no call-out fee. Call 0172 223 9611.

Costs vary by property and scope. We provide free surveys and written fixed-price quotes across Salisbury and surrounding areas. Call 0172 223 9611 to arrange.

Yes — all surveys and quotes are completely free with no obligation. We assess, confirm the issue, and give you a written quote. Call 0172 223 9611.

Yes. NFRC registered, fully insured with £5m public liability, 10-year written workmanship guarantee on all work. Call 0172 223 9611.

Yes — 24/7 emergency cover across Salisbury and all surrounding areas. No call-out fee. Call 0172 223 9611.

Over 20 years covering Salisbury and surrounding Wiltshire areas. We know the local housing stock well. Free survey — call 0172 223 9611.

We are Salisbury-based and can reach most of the city within 20 minutes. Surrounding villages within 30-45 minutes. 24/7 emergency attendance. Call 0172 223 9611.

Last updated: August 2026

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