Repair
- Suits isolated splits, blisters or failed edges
- Keeps the existing structure and covering in place
- Can extend the working life of a sound felt layer
- Does not correct widespread failure or poor falls
Roofing
Felt Flat Roofs: Repair and Replacement
Felt flat roofs are built from layers of bitumen-based roofing felt, sealed together and to the deck beneath. They are common on garages, extensions and flat sections of homes. Here is how we decide between repair and replacement.
How a felt roof is built
Bitumen is a black, tar-like material that waterproofs when it is applied in layers. A traditional felt roof uses several layers, often finished with a mineral-surfaced top sheet that protects the surface from sun and weather. The layers may be bonded with hot bitumen, cold adhesive or torch-applied methods, depending on the system and its age.
Felt roofs depend on falls to move water and on upstands to seal the edges. Because felt is built up in layers, faults often sit beneath the surface, which is why a visual check does not always reveal the full condition.
Early warnings
Signs of a tired felt roof
Felt ages through sunlight, temperature movement and water. Look for these signs, and remember that many are only visible from a safe distance.
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Blisters and bubbles
Raised areas can indicate trapped moisture or air beneath the surface. Blisters that split open can let water in and expose the layers below.
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Cracked or split felt
Cracks, especially along joints or at upstands, let water reach the layers below. They often appear first where the felt has been stretched by temperature movement.
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Ponding and puddles
Water lying on the surface for long periods can break down the felt and encourage leaks. It is often a sign of lost falls or blocked outlets.
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Damp ceilings
Staining or damp in the room below a flat roof is a clear reason to arrange an inspection, even if the roof looks intact from the ground.
Options
Repair or replace a felt roof
A felt roof can often be repaired for many years, but there is a point at which replacement is more sensible. The survey shows where that point falls for your roof.
Replacement
- Suits widespread failure across the surface
- Allows the deck, falls and edges to be corrected
- Gives a new waterproof layer with fresh detailing
- Involves more disruption and waste to clear away
Free survey
Is your felt roof due a look?
We inspect the surface and edges, explain what we find, and set out whether repair or replacement makes more sense. You receive the explanation in writing, and no work is carried out without your agreement.
The process
How a felt roof is repaired or replaced
Repair and replacement follow the same logic: the base is prepared, and new material is bonded to sound layers. The steps below show a typical replacement.
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Survey and scope
We confirm the condition of the deck and layers, and agree the scope in writing. Where it is unclear what lies beneath the surface, we say so.
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Stripping the old layers
Old felt is removed where the deck or the layers are failing. The deck is inspected for rot, movement and fixings, and repairs are made before anything new goes on.
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Falls and insulation
Falls are formed or refreshed so water reaches the outlets. Any insulation that is wet or damaged is replaced, because it cannot be left in place beneath a new roof.
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Laying the felt
Base sheets and top sheets are laid in courses, with laps (the overlap between sheets) set to the manufacturer’s requirements. Each layer is bonded so that water cannot track between them.
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Upstands and finish
Upstands are formed at walls and edges, and the top layer is finished with a surface suited to the roof. Outlets and penetrations are sealed and checked.
Upkeep
Keeping a felt roof in order
A felt roof lasts longer when small issues are dealt with early. These habits are simple to keep.
- Keep outlets, gutters and hoppers clear of leaves, moss and debris
- Check the surface from ground level after storms for splits or displaced material
- Report any ponding water so the fall can be reviewed
- Keep an eye on the edges and upstands for lifting or gaps
- Avoid placing equipment, planters or bins on the roof without advice
- Arrange an inspection before the roof is put to any new use
Where felt roofs tend to fail
Edges and upstands are where most felt problems begin. The felt is turned up against walls and kerbs, and it is exposed to rain running across the surface, sunlight and movement where the building meets the roof. If the top edge of an upstand is not properly secured, water can creep behind it and reach the layers below without showing on the surface. Lifting at the edges is therefore one of the first things we check.
Outlets matter as much as the surface. A blocked or undersized outlet holds water against the felt, and standing water shortens the life of the top sheet. We clear and inspect outlets as part of a survey, and we can advise whether a larger or additional outlet would improve drainage. Please do not climb onto the roof to clear them yourself.
Questions
Felt roof questions
Questions homeowners ask about felt flat roofs.
How long does a felt roof last?
Felt life varies with the specification, exposure and maintenance. Older felt can become brittle and fail in sections, while well-maintained felt can give many years of service. We cannot give a fixed timescale without seeing the roof.
Can you patch a felt roof rather than replace it?
Often yes, where the damage is limited and the deck is sound. Patching a widespread problem can waste money, so we tell you where a repair is likely to hold and where it is not.
Will a new felt layer be laid over the old one?
Sometimes, but overlaying is not always suitable. It depends on the flatness, the condition of the existing layers and the weight the roof can carry. We confirm the method in the survey.
What is the difference between hot and cold application?
Hot-applied systems use molten bitumen, which must be handled with great care and is generally a job for trained installers. Cold-applied systems use adhesives. Both can perform well when correctly applied, and the right choice depends on the roof and the system specified.
Is it safe to remove old felt?
Older felt can contain asbestos in some cases, and its dust and fragments can be harmful. Do not cut, strip or disturb old material yourself. Ask us to explain the testing and handling needed before any removal begins.
Where we work
Roofers serving five regional areas
We work across five regional areas: North London, North West London, West London, Hertfordshire, Buckinghamshire. Not sure if we cover your street? Call us on 01632 960123, or see all areas we cover.
Next step
Discuss your felt roof
We can look at your felt roof and explain your options in plain language. Get in touch through the contact page to arrange a survey.