Caring for a Felt Flat Roof

Maintaining a felt flat roof comes down to four annual habits: keep gutters and outlets clear, inspect overlaps and upstands for splits, watch for blisters and ponding water, and book a yearly health check so faults are caught before they leak. A modern built-up felt roof that gets this attention will comfortably last 20 years or more.

Felt suits garages, blocks of flats, rear extensions and commercial buildings particularly well, and it is one of the most common flat-roof coverings on Edinburgh’s tenements and rear additions. The material once had a reputation for being short-lived, but modern built-up felt (often three layers of polyester-reinforced bitumen, torch-applied or cold-bonded) is a different proposition to the single-layer pour-and-roll felt of decades past.

Here is how to keep yours in good condition, along with the checks worth carrying out each year.

The annual felt-roof checklist

Run through these five checks once a year, ideally in autumn before the worst of the weather arrives:

• Clear gutters, hoppers and rainwater outlets. Blocked drainage lets water pool on the felt, the most common cause of premature failure.
• Inspect the overlaps between sheets and confirm they are tight and fully sealed.
• Check the upstands and flashings where the roof meets a wall or kerb for cracks or splits in the mortar or sealant.
• Look for blisters in the surface and note their size.
• Watch for ponding that sits on the roof more than 48 hours after rain, a sign of failing falls or a sagging deck.

Clear leaves and debris

Make sure gutters and rainwater outlets stay free-flowing and clear. Blocked outlets let water pool on the felt, which is one of the most common causes of premature failure. On Edinburgh roofs overhung by mature trees, leaf fall and moss washed down from neighbouring slate can clog outlets within a single season.

Only carry out checks at height if you have the right equipment, you are supervised, and you are confident doing so. If access is awkward, leave it to a roofer.

Check the surface and detailing

Look over the overlaps between sheets and confirm they are tight and sealed. Check that upstands are securely fixed to the wall, with no cracks or splits in the mortar or sealant.

Keep an eye out for blisters forming on the surface of the felt. Note their size, and if they start to expand, report them to your roofer. Growing blisters often signal trapped moisture beneath the membrane.

Watch for condensation

Internal condensation is something you will not see on the roof itself, but it matters just as much. It usually points to insufficient insulation or poor ventilation. Left unchecked, it can rot timber supports and, over time, lead to structural problems.

If you suspect condensation inside the building, get it assessed rather than waiting for visible damage to appear.

Book an annual check

These checks are worth carrying out once a year. If you would rather not do them yourself, or access is difficult, a roofer can carry out an annual roof health check on your behalf.

Getting familiar with what a healthy roof looks like makes it far easier to spot when something is off, even if the repair itself needs a professional.

When to recover rather than repair

Spot repairs work well for isolated faults. But once a felt roof shows widespread blistering, lifting overlaps, or surface that has gone brittle and is cracking across large areas, patching becomes a losing game. At that point recovering or replacing the roof is the more cost-effective route.

If you are not sure which side of that line your roof is on, that is exactly the kind of judgement a roof survey and report settles. For wider context on why felt and other flat systems are worth maintaining, see our guide to the benefits of a flat roof.

Get in touch

We work across both residential and commercial flat roofing, and we are happy to advise on repairs, maintenance or a full recover. For more information or to arrange a roof health check, get in touch with the team.