How Much Does It Cost To Build An Extension?

Posted by Tim Foster on May 17, 2022 2:23:29 PM

Abbots Bromley Extension Exterior View 2

This is often the first question we get asked! We understand every client wants to receive quality and value so we’ve put together this guide to help you plan for costs, and gain familiarity with the variables which affect price.

We recommend budgeting between £2'000 - £3'000 per square metre. Obviously, there is quite a difference here, however this covers both single and double height structures, options for building materials and the amount of glazing incorporated etc.

The Site

Soil structure can affect the type of foundations required. It’s vital to account for existing structures and the positioning of services and utilities to the property such as gas, electricity and water. Building near trees, drains or sewers can increase the cost of groundwork.

Access is another key consideration. Can materials be transported easily to and from the site? Factoring additional transportation or lifting equipment such as cranes will need to be budgeted for.

BDS Architecture will always perform a free consultation to establish the scope of work involved, including the level of internal and external alteration required, for a beautiful result.


Costs of building materials and contractors can differ dramatically for different areas in the UK. With vast experience in the design, planning and building stages, BDS Architecture can negotiate the best rates for quality materials, whilst taking responsibility for the build. This also removes the pressure of sourcing reliable contractors. We specialise in sourcing external materials to compliment the original building, for a seamless result, wherever your location.

Chartered Residential Architect Vs Architectural Design Service

A Chartered Architect’s fees are usually 10-15% of the overall cost for residential extensions. Architectural design services, such as BDS Architecture, provide the same service as a Chartered Architect but with the advantage of also offering an in-house building service through our sister company BDS Construction. This ensures there is no disconnect between the design vision and the practical implementation of the design. An additional benefit is one point of contact, as full project management is included within the quotation. Where labour costs typically represent between half and two thirds of the cost of an extension, receiving the full package from one company at a fixed agreed price can prevent costs from spiralling and keep your project on track.

The Design

A simple design will be less expensive, for example square or rectangular footprints will cost less than a curved design. Standard sized doors will cost less to source than manufacturing bespoke designs. In the same way, standard building materials will be readily available, therefore cheaper to source.

Whilst quality should always be ensured throughout every build, premium choices will increase costs. By choosing an Architectural design service with an overall knowledge of building practices and material costs, you’ll be advised on how to create high end looks in the most cost effective way.

Balancing Costs Against The Value Of Your Home

If you are looking to develop your property as an investment, it’s important to balance the costs of extending against the increased market value of your property, after the end result. This is less of a priority if the extension is more about fulfilling lifestyle changes in your forever home, or creating a fresh space to enjoy life. An extension will add considerable value and desirability to your home, whatever your reasons.

Contact us today for a free consultation or click here to access our free e-book: The Ultimate Guide To Extending Your Living Space. Transforming your home with BDS Architecture could cost much less than you think!

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Topics: Extensions

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