House extension cost: a price guide for London

Although it is difficult to determine extension costs prior to obtaining a quote from a builder, the following figures give an indication for work in London:

A creatively designed terraced house extension, featuring large areas of glazing may bear a construction cost of around £40,000.

The subsequent fit-out will be in addition to this construction sum. This figure will be more variable and depend on the preferences of the homeowner, for example, stone flooring may have a greater cost implication than timber alternatives. As a guideline, the fit-out cost may be between £10,000 and £20,000 for a single storey extension.

A more accurate cost indication for your extension may be obtained at the planning stage of your project. At this time, the outline design is complete, and plans are sent to the local authority. Your builder will then be able to give an indicative estimate for the work.

Modern kitchen extension in brick and glass, Highgate

An estimate will develop into a fixed quote for your extension when detailed, post-planning architectural drawings have been produced and your builder has visited the property to discuss your requirements and survey the site conditions. This quote will form part of a contract between the client and the builder that will be signed by both parties before work begins on your extension.

Once work has begun on site, payments are normally made to the builder at monthly intervals.

It is wise to ensure that there is a contingency sum included in any quote obtained. This sum will only be used to pay for unforseen additional costs should they occur. On average, around 5% of the quote is sufficient for a typical extension. If the contingency was not required, it will be deducted from the final bill once works are complete.

Please visit 'Construction Services' to find out more about AfL Construction Limited and obtain a free quote, or visit 'Our Ideas' to find out more about our architects' previous work.