Flat roof or pitched roof for an extension?
Flat roofs suit modern designs, give more ceiling height and make roof lanterns easy; modern single-ply, EPDM and GRP systems perform well when properly installed. Pitched roofs blend with traditional houses and allow vaulted ceilings, but need more height and cost slightly more, about £1,850 to £3,500 per m² against £1,750 to £3,350 per m².
Height is often the deciding factor
A lean-to pitched roof has to start below the first-floor windows. On many houses that leaves little room for a pitch deep enough for tiles, so a flat roof is the only way to get a good ceiling height inside.
Modern flat roofs
A warm flat roof puts the insulation above the deck, with a membrane on top laid to falls. Single-ply PVC or TPO, EPDM rubber and GRP fibreglass are all proven when detailed properly at the edges, outlets and upstands.
When pitched roofs make sense
- Period, rural and cottage-style houses.
- Conservation-sensitive streets.
- When you want a vaulted ceiling with roof windows.
Lanterns and rooflights
Both roof types can have glazing. Flat roofs take lanterns and flat rooflights; pitched roofs take roof windows set into the slope.
This guide is general information, not legal or professional advice for your property. Rules can change; we check the current position for your address at the survey.