Pricing guide
What an extension costs per square metre in 2026
Most builders will not put a number on a page. We do, because you cannot plan a project without one. The figures below are the prices we actually work to, built from our own labour rates, trade material costs and a margin that lets us stand behind the work with a written guarantee. They are guide figures, not a quote. A line by line fixed price follows a site visit.
All prices are per square metre of new internal floor area and exclude VAT. They are for single storey rear extensions on a straightforward site. Side returns, double storey work, tight access and conservation area detailing move the figure, and we tell you which way at the site visit.
Three ways to build with MCS
Choose how much you want us to take on. Every tier is a fixed price contract with a named project manager, a written programme and stage payments tied to inspected work.
Structural Envelope. We build the shell: groundworks, foundations, drainage, walls, structural steel, roof, insulation and floor slab, weathertight and signed off by Building Control. You supply the glazing and we fit it. You then finish the inside yourself or with your own trades.
Structural and Trade. The envelope plus every trade to make it a finished room: first and second fix electrics, plumbing and heating, plastering and screed, decoration. You buy the glazing, kitchen, sanitaryware, tiles and floor coverings and we install them.
MCS Combined Value. Everything under one contract, including the supply of glazing, a kitchen allowance, sanitaryware, tiles and floor coverings. One price, one project manager, one handover.
Guide prices per square metre, ex VAT
Structural Envelope: medium specification from £2,125 per m², high specification from £2,700 per m².
Structural and Trade: medium specification from £3,325 per m², high specification from £4,300 per m².
MCS Combined Value: medium specification from £4,100 per m², high specification from £5,825 per m².
What a typical 30 m² kitchen extension comes to, ex VAT
Structural Envelope: £63,750 medium specification, £81,000 high specification.
Structural and Trade: £99,750 medium specification, £129,000 high specification.
MCS Combined Value: £123,000 medium specification, £174,750 high specification.
Add 20% VAT on top for work to an existing home.
What medium and high specification mean
Medium specification. A straightforward footprint, 2.4 metre ceilings, standard facing brick to match the house, warm flat roof in GRP or EPDM with two roof lights, insulation to current Building Regulations, uPVC or aluminium bifold or sliding doors, a mid range kitchen allowance of around £6,000 and porcelain or engineered floors.
High specification. A more complex footprint or a pitched roof, 2.7 metre or taller ceilings, handmade or reclaimed brick or a rendered and clad finish, slate or zinc roofing, insulation beyond the regulations minimum, slimline aluminium or steel framed glazing, a kitchen allowance of around £12,000 and premium stone, tiled or hardwood floors.
What moves the price
Access and parking. Terraced houses with no side access mean everything comes through the house or over a neighbour. Allow 10 to 15% more.
Side return and wraparound extensions. Stitching into the existing structure and working in a narrow strip adds labour. Allow 15 to 20% more per square metre than a plain rear extension.
Double storey. Often cheaper per square metre because one roof and one set of foundations serve two floors. Allow 5 to 10% less per square metre on the upper floor.
Ground conditions. Clay near trees, drains under the footprint or a high water table can mean deeper or piled foundations. This is priced after the site visit and the engineer’s design, never guessed.
Small extensions. Under 20 m² the fixed costs of setting up, scaffolding and Building Control are spread over fewer metres, so the per metre rate rises.
How we price and how you pay
Every job is priced from your architect’s drawings and the engineer’s design. You get a line by line breakdown by trade and stage, not a single figure, so you can see exactly where the money goes and compare us fairly.
A 10% deposit at signing covers the structural engineer, party wall surveyor, site surveys and Building Control. After that you pay at agreed milestones as stages are finished and inspected. Nothing is paid in advance for work that has not been done.
Guide prices reviewed September 2026 and based on MCS Renovations’ own labour and material costs. Every project is priced individually after a site visit. Figures exclude VAT, design and planning fees, party wall awards and any works to the existing house beyond the extension.