Flat roofs have a reputation for being short-lived, but that reputation is largely based on old-style felt installations from the 1970s and 80s. Modern flat roof systems can last 25 years or more, if they are installed correctly.
The three main types of flat roof and their lifespans
GRP Fibreglass
25–50 yearsOur recommendation for most domestic flat roofs. The long-term value is excellent.
EPDM Rubber
25–50 yearsExcellent for extensions and outbuildings. Handles the coastal Dorset climate well.
Felt (3-layer)
10–20 yearsStill a valid option for outbuildings or where budget is the primary concern, but we always recommend GRP or EPDM for living spaces.
5 ways to extend the life of your flat roof
- 1
Keep drains and outlets clear
Pooling water is the single biggest cause of flat roof failure. Clear outlets every autumn and after heavy storms.
- 2
Inspect annually
Walk around and look for blistering, cracking, or lifted edges. Catching a small issue early costs a fraction of the price of ignoring it.
- 3
Don't walk on it unnecessarily
Unless it's a GRP or ballasted roof designed for foot traffic, minimise walking on flat roofs. Even small punctures can allow water ingress.
- 4
Trim overhanging branches
Leaves and debris trap moisture and accelerate moss growth. Overhanging branches can also physically damage the membrane.
- 5
Deal with moss and algae promptly
Moss roots penetrate felt and can lift EPDM bonding at edges. A soft wash treatment every few years prevents buildup.
When to replace rather than repair
If your flat roof is a traditional felt system and is approaching 15 years old, repeated patching becomes a false economy. Signs that point to a full replacement include:
- +Multiple areas of blistering or cracking
- +Persistent damp patches on the ceiling below even after repair
- +Visible daylight through the roof deck (rare, but it happens)
- +The roof has been patched more than twice in five years
Flat roof advice or quote in Dorset?
We install GRP and EPDM flat roofs across Dorset. Free site assessments.