Home extension costs vary greatly depending on many factors such as the extension size, type of materials, site conditions, how the space is to be used and also your location in the UK. Simple extensions are obviously the most affordable. Build costs are usually calculated using the square metre floor area of the proposed living space.
The simple guide costs illustrated below would be for constructing the shell of the extension only – which would not include the price of any fixtures and fittings such as kitchens, bathrooms, cloakrooms etc.
House Extension Costs
The square metre extension cost is arrived at by first measuring the proposed inhabitable floor area of the planned extension to the internal walls. So, on a proposed two-storey extension, if this is 5 metres long and 4 metres wide downstairs, and the same upstairs, the calculation would be 5m x 4m = 20 metres square x 2 (upstairs & downstairs) = 40 metres square overall.
The square metre costs below are for guidance only and do not include any fitting out.
Home Extension Square Metre Estimated Costs
LOW SPEC (PER SQM)
MID SPEC (PER SQM)
HIGH SPEC (PER SQM)
£1,000 to £1,600
£1,700 to £2,000
£2,200 to £4,000 and up
8 to 12 weeks
£1,200 to £1,900
£2,000 to £2,200
£2,300 to £4,000 and up
12 to 20 weeks
Single and Two Storey Extension Costs
As a guide, a 30 square metre single storey extension built on a low spec budget may cost between £30,000 to £48,000. If you can afford more, a mid spec extension of this size may cost between £51,000 and £60,000. These prices exclude any fitting out costs.
If you want to construct a two-storey extension, the costs per square metre are not significantly higher. Building companies will usually quote by the square metre, not on the number of storeys.
Both single storey and two-storey extensions require foundations and a roof, so the main additional costs you will need to consider are scaffolding, extra material for the floor joists and walls, heating, plumbing, and electrics, as well as the quality of fittings you choose.
On average, a 40 metre square two-storey extension may cost anywhere from £48,000 to £76,000 if you are working on a low spec, or between £80,000 and £88,000 if your budget is more flexible.
A two-storey extension measuring 60 square metres may typically cost in the range of £72,000 to £114,000 for a low spec or £120,000 to £132,000 for a mid spec build.
If you would like more information or to request a quotation, please call us on 08448 794819 or complete the enquiry form below and we will get back to you as soon as we can.