Felt has a poor reputation earned by cheap single-layer work from decades ago. Modern high-performance torch-on systems are a different product: polymer-modified bitumen membranes in two or three layers, heat-welded together, with proper detailing at upstands and outlets. Done properly, they are a durable and cost-effective covering.
Layers, not layer
The performance of a felt roof comes from building it up. A vapour control layer or underlay is bonded first, then intermediate and cap sheets are torched on with staggered laps so no joint sits above another. A mineral-finished cap sheet gives the UV protection. A single layer of felt nailed down is not a roofing system and never was.
Where felt still wins
It is the most economical of the three common domestic systems, it handles awkward shapes and multiple penetrations well because it is applied in pieces, and it repairs easily, a competent roofer can weld in a new patch that is chemically continuous with the original.
- Budget-sensitive replacements on outbuildings and garages
- Roofs with many penetrations, upstands or changes of level
- Repairs and localised overlays to existing felt roofs
- Situations where hot work is acceptable and safe
Its weaknesses
It is the least tolerant of the three systems to standing water, so falls really matter. It blisters where moisture is trapped below, and it becomes brittle with age and UV exposure. Torch-on work also involves a naked flame, which needs proper hot-work precautions and rules it out in certain situations, close to timber cladding, thatch or on some occupied commercial buildings.
Repair or replace an existing felt roof
Localised damage on a roof that is otherwise dry and well drained is worth repairing. Widespread blistering, a soft deck, or a roof that has already been overlaid once means replacement, and it is usually the moment to consider whether EPDM or GRP suits the roof better going forward.
Common questions
How long does a torch-on felt roof last?
A properly specified multi-layer system commonly gives 15-20 years. Cheap single-layer work gives a fraction of that, which is where felt's reputation came from.
Is felt cheaper than EPDM?
Usually yes on initial cost. Over the lifetime the gap narrows considerably, so it is worth comparing both when a roof is being replaced rather than repaired.
Can felt be laid in winter?
It is less weather-dependent than GRP, but it still needs a dry deck and safe conditions for hot work. We will not torch onto a wet substrate.
Can you patch my existing felt roof?
Where the roof has life left in it, yes, welded-in patches integrate well. We will tell you if patching is simply postponing an inevitable replacement.