What replacing a flat roof on a garage, extension or dormer costs in Medway, why EPDM and GRP are priced differently, and when a repair is the better spend.
Flat roof pricing is usually quoted per square metre, and the covering you choose matters as much as the size. Here's how the options compare and what changes the number.
The Coverings, And How They Compare
- High-performance felt — the cheapest option and a proven system, though it has the shortest life of the three
- EPDM rubber — mid-range, seamless, and copes well with temperature movement. The usual choice for domestic extensions and garages
- GRP fibreglass — the most expensive of the three, but gives a hard-wearing, walk-on finish. Common on balconies and flat roofs people need to access
- Liquid coatings — good value for awkward shapes and for overlaying a sound existing roof
What Changes The Price
- Size, obviously — but larger roofs cost proportionally less per square metre
- Whether the deck is sound. If the boards underneath are spongy or the insulation is wet, no covering will last until the deck is replaced — and that's real extra cost not visible from the ground
- Existing layers. Old felt roofs often have two or three layers up there, all of which have to come off and be disposed of
- Edges, upstands and outlets — cutting and dressing the membrane around a parapet takes longer than the flat area itself
- Access and scaffold, as with any roof work
Repair Or Replace?
If the roof is under 10–15 years old, the deck is solid and the problem is localised — a small split, a leak at a flashing, ponding you can fix by adjusting the fall — a repair is money well spent. If it's over 20 years old, leaking in more than one place or the felt has shrunk and cracked across the surface, replacement is cheaper over the next five years than another round of patches.
One Thing To Insist On
Anyone quoting you a new membrane without checking the deck from underneath is skipping the part that decides whether the job lasts. We survey the deck as well as the covering, and we'll tell you honestly if the covering is fine and something else is at fault.
Free surveys and written quotes on flat roofs across Chatham, Gillingham, Strood, Rainham and Walderslade.
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Costs and timings in this article are guides for Medway and Kent properties. Every roof is different — a survey is the only way to get an accurate figure.