Why flat roofs wear differently
A pitched roof sheds rain in seconds. A flat roof, which is never truly flat but laid to a gentle fall, moves water slowly towards a gutter or outlet. That means the surface spends more time wet, sees more direct sun and takes the full force of frost. The covering has to be completely watertight, because there is no overlap of tiles to fall back on.
What shortens a flat roof's life
A handful of things do most of the damage:
- Ponding: puddles that sit for days because the fall is poor or the deck has dipped
- Weak edges and upstands, where the covering meets a wall, trim or gutter
- Foot traffic on a roof that was never meant to be walked on
- Strong sun drying out and cracking older felt
- Blocked outlets and gutters forcing water back across the surface
Felt, GRP and EPDM in general terms
Traditional felt is built up in layers with bitumen. It is familiar and cheap to lay, but older felt in particular dries out, blisters and cracks with time. GRP fibreglass forms a hard seamless shell. EPDM rubber is a single flexible sheet. Both modern systems tend to resist the problems that wear felt out, provided the deck is sound and the detailing is right. We explain the differences properly in GRP vs EPDM flat roofs.
We do not put a number of years on any of them, because how the roof was laid and looked after counts for more than the material name.
Warning signs of failure
Look out for bubbles or blisters on felt, cracks that look like crazy paving, splits along joints, and edge trims that have lifted. Indoors, a brown ring on the ceiling of the extension or a damp smell in the garage is a strong clue. If the roof feels soft or bouncy when you press on it from a ladder, the deck itself may be wet, and that usually means a replacement rather than a patch.
If water is already coming through, read our page on a leaking flat roof.
Simple upkeep that helps
A couple of times a year, and after autumn leaf fall, clear outlets and gutters so water can escape. Brush off moss, leaves and debris, which hold moisture against the surface. Keep tree branches cut back so they do not rub. Avoid standing ladders or furniture directly on the covering. Most of this can be done from a ladder at the edge without walking on the roof.
Repair or replace
If the trouble is one split or a lifted edge and the rest is firm, a targeted repair can be good value. If blisters and cracks are everywhere, the deck is soft, or the roof has been patched several times already, a full replacement in GRP or EPDM is usually the better spend. Our flat roofing page shows how we strip and relay a roof, and the flat roof replacement cost guide explains what decides the price.
Lee Draper will look at yours for free and tell you honestly which route makes sense. Call 07947 758052 or get in touch online.
Questions to ask about an existing flat roof
If you have just moved into a house with an extension or garage, it is worth finding out what you have. Ask the previous owner or check the paperwork for when the roof was last done and what it was covered with. Look at it from an upstairs window: is the surface even, are the edges neat, is water draining towards the outlet? Check the ceiling underneath for any old stains that may have been painted over.
That simple look will tell you whether to keep an eye on it or get someone to check it now. A flat roof that is nearing the end of its life is far cheaper to replace on your timetable than after the first heavy storm has soaked the deck and the room below. If you are unsure, ask Lee to take a look while he is nearby.