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Wondering how much a house extension costs in London?
Whether you’re planning a rear extension, side return, wrap-around or double-storey extension, understanding the costs involved helps you budget with confidence. This guide explains average extension prices, the factors that affect costs and how to get the best value for your investment.
Extension prices vary depending on the size, specification and complexity of the project. As a general guide:
Extension type Typical cost
Small Rear Extension £45,000 - £70,000
Single Story Extension £55,000 - £95,000
Side Return Extension £50,000 - £ 90,000
Wrap Around Extension £80,000 - £140,000
Double Story Extension £90,000 - £180,000+
Every property is different. We provide fixed quotations following a free site visit.
Several factors influence the overall cost of an extension.
Larger extensions require more labour and materials.
Removing load-bearing walls and installing steel beams (RSJs) increases costs but creates beautiful open-plan living spaces.
Ground conditions determine how deep foundations need to be.
If your extension includes a new kitchen or bathroom, these are often among the biggest costs.
Large sliding or bi-fold doors cost more than standard uPVC windows.
Flooring, decorating, lighting and bespoke joinery all affect the final budget.
A standard extension usually follows this schedule:
Most projects take between 8 and 16 weeks, depending on their size and complexity.
Ways to Keep Extension Costs Under Control
Is a House Extension Worth It?
For many London homeowners, an extension is more cost-effective than moving house.
Benefits include:
Why Choose Rocko Construction Ltd?
How much does a single-storey extension cost?
Most single-storey extensions in London cost between £55,000 and £95,000, depending on size and specification.
Do I need planning permission?
Some extensions fall under Permitted Development, while others require planning permission. We can advise you during your consultation.
How long does an extension take?
Most projects take between 8 and 16 weeks.
Can you manage the whole project?
Yes. We coordinate everything from planning and structural work through to decorating and final completion.
Do you offer free quotations?
Absolutely. We provide free consultations and fixed quotations with no obligation.