Extension costs, build cost per m2

How much will it cost to build an extension?

This is the question quite often asked by our clients looking to extend their property.

There are guidelines and prices per m2 for certain diciplines but it really depends on the following factors:

-) Size & complexity. Is it a straightforward rear extension with a sloping roof or a L shaped design with a cut roof?

-) Choice of materials. Standard or specialist matreials ad fixtures & fittings.

-) Date of commencement and size of the building firm. Building in quiet times is cheaper and usually a smaller firm hassmaller overheads which they can pass onto you.

-) Involvement. Do you want to project manage yourself? Maybe decorate yourself? This all saves cost.

-) Site location & landscaping. Is your site easily accesible, is it sloping and what soil conditions? This depends on how deep you would have to dig for foundations and how much the landscaping would need to be addressed. Also an extension in London would cost more than a house extension in Northampton.

-) Professional fees. Architectural drawings, Building control fee, Planning fee, Structural Engineers cost, etc.

On average a single storey extension would cost around £1200-1400 per m2

A double storey extension around £1600 per m2

Planning costs are usually around £1000 for the Architectural Drawings, around £500 for Building control inspections and certificate and another £500 for Structural engineers involvement.