How Much Does a Single-Storey Extension Cost?
£22,000 – £55,000
depending on size
A single-storey extension costs between £22,000 and £55,000 depending on its footprint, specification, and location. Smaller rear extensions of 3x4m are at the lower end; larger wrap-around or side-return extensions with high-spec glazing and finishes push costs significantly higher. Most single-storey rear extensions fall under permitted development and do not require planning permission.
Average cost
£22,000 – £55,000
depending on size
Prices vary by region, property type and tradesperson. Always get at least two quotes.
What affects the price?
Footprint size - a 3x3m extension costs far less than a 5x6m rear wrap-around in both materials and labour
Roof type - a flat roof with rooflight costs less than a pitched or lantern roof; large skylights add £2,000-£8,000
Glazing - standard French doors are cheapest; bifold or sliding doors add £3,000-£12,000 depending on width
Internal fit-out - the shell build cost is separate from flooring, plastering, electrics, plumbing, and decoration
Labour vs materials
Build costs for a single-storey extension typically run at £1,800-£2,200 per m2 for the shell. Labour represents around 40-50% of this figure. A 15m2 extension takes approximately 8-12 weeks from groundworks to practical completion.
Questions to ask your tradesperson
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