Single-storey extension cost: what it really costs in 2026
A Qome Snap Guide: quick, honest and no guff. Approximate figures, adjusted to your region inside Qome.
Snap answer
£2,400 – £4,800 /m²
Budget from about £2,400 per square metre for a standard finish, £3,600 premium, and £4,800 at architect-designed spec. A typical 15m² extension starts around £32,000 all-in.
Takes10–16 weeksDisruptionGarden becomes a site; the knock-through week is the disruptive one
Cost at a glance
Option
Best for
Guide range
Standard spec
Good quality, straightforward design
£2,400 /m²
Premium spec
Higher-end glazing and finishes
£3,600 /m²
Architect-designed
Structural glazing, bespoke details
£4,800 /m²
Approximate guide figures, not quotes, Qome adjusts every price to your region.
What actually happens
Design, drawings and structural calculations
Foundations dug and poured (the messy fortnight)
Walls up, steels in where the house is opened
Roof on and made watertight, the turning point
Windows and doors fitted; first-fix services
Plastering, screed and underfloor heating if chosen
Second fix, decoration and the knock-through tidy-up
Price by region
Starting figures by region, the same honest baseline, adjusted for where you live.
London (Inner)from £3,700 /m²
London (Outer)from £3,200 /m²
South Eastfrom £2,900 /m²
East of Englandfrom £2,600 /m²
South Westfrom £2,500 /m²
Scotland (Highlands)from £2,300 /m²
West Midlandsfrom £2,300 /m²
North Westfrom £2,200 /m²
East Midlandsfrom £2,200 /m²
Scotland (Central)from £2,200 /m²
Yorkshirefrom £2,200 /m²
Walesfrom £2,100 /m²
North Eastfrom £2,000 /m²
Northern Irelandfrom £1,950 /m²
Popular choices
Bifold or sliding doorsRoof lanternsCrittall-style glazingPolished concrete or large-format tiles
Rules & regulations
Many rear extensions fall under permitted development (up to 4m, or 6m with neighbour consultation on semis/terraces), beyond that, planning permission
Building regulations always apply, with staged inspections
Party Wall Act notices are usually needed when building near a boundary
Snap tips
The watertight stage is the milestone that de-risks everything after it
Hold 10–15% contingency; ground conditions are the classic surprise
Price it properly on Qome
Choose your options and see an honest, region-adjusted estimate, free.