Flat vs Pitched Roof for an Extension
On most single-storey rear extensions you have a real choice between flat and pitched. The right answer depends on planning constraints, eaves height, and whether you ever want a loft above.
Flat Roof (EPDM)
Side and rear extensions where eaves height is constrained.
- Lowest profile — keeps under permitted-development height limits
- Faster to build
- Cheaper structure
- No loft space above
- Visible from above on stepped properties
- 25–35 year lifespan vs 60+ pitched
Pitched Tile
Extensions where eaves height allows, or where matching the main roof matters.
- Matches the main house
- 60+ year lifespan
- Allows attic / storage space
- More expensive build
- Eaves height often pushes you out of permitted development
- Heavier structure required
Our honest verdict
If you're against an eaves height limit (common on rear extensions on terraces), EPDM flat is usually the only practical answer. If you've got eaves room and want it to match the house, pitched tile is the long-term winner.
Local angle
On Burnley and Nelson terraces, eaves height almost always forces flat. On Fylde Coast bungalows with low main eaves, pitched matching is usually the right call.
Will a flat extension roof leak in 10 years?
Felt ones often did. EPDM with a 20–25 year manufacturer warranty doesn't — provided the deck is solid and the upstands are properly dressed.