How Much Does a Pitched Roof Extension Cost in 2026? (UK)
A pitched-roof single-storey extension typically costs £2,400–£3,200 per m² fitted in 2026. A small 3x3m extension is around £25,000–£35,000; a popular 4x5m kitchen extension runs £50,000–£65,000; a large 6x6m can reach £85,000+. Pitched roofs add 10–20% over a flat-roof equivalent but last longer and add more resale value.
Pitched roof extension cost by size (2026 UK)
Costs scale with footprint. As a 2026 UK guide: 3x3m (9m²) around £25,000–£35,000; 4x4m (16m²) around £40,000–£52,000; 4x5m (20m² — the most popular kitchen size) around £50,000–£65,000; 5x6m (30m²) around £70,000–£85,000+. All figures assume standard foundations, brick-and-block cavity walls, plastered finish, a tiled pitched roof, basic glazing and a builder included in the FMB or TrustMark.
How the roof finish changes the price
Concrete interlocking tile is the cheapest (£50–£70 per m²). Clay plain tile is mid-range (£80–£120 per m²). Natural slate is premium (£120–£180 per m²). Standing-seam zinc or aluminium is the most expensive (£180–£260 per m²) but is increasingly popular on modern pitched extensions with shallow pitches. The choice typically adds or subtracts £2,000–£6,000 on a 4x5m extension.
Glazing, rooflights and extras
Most pitched-roof extensions include rooflights or a roof lantern: Velux or Fakro rooflights at £1,500–£2,500 fitted each, roof lanterns at £2,500–£4,500 fitted. Bifold or sliding doors add £5,000–£9,000. Steel beams for a knock-through opening add £2,500–£5,000 including structural calcs. Underfloor heating adds £2,500–£4,500. A new fitted kitchen and worktops adds £12,000–£25,000 on top.
Pitched vs flat roof — cost difference
A pitched roof typically costs 10–20% more than a flat-roof equivalent due to extra timber, tiling labour and material. The trade-off: a tile pitched roof lasts 50–60 years versus 20–25 years for EPDM flat — and adds an estimated 1–2% more home value on resale.
How to budget step by step
1. Confirm the m²
Pitched-roof extension cost scales with footprint at roughly £2,400–£3,200 per m² fitted.
2. Pick the roof finish
Concrete tile is cheapest; clay mid-range; slate or zinc premium.
3. Decide on rooflights and glazing
Rooflights, lanterns and bifolds shape the headline price more than the base build.
4. Compare three matched quotes
FMB or TrustMark members, on the same written scope.
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