House extension services in London
Build Team designs and builds side return, rear, wraparound and kitchen extensions, loft conversions and loft extensions across London, and handles the party wall process for each one. One team takes the project from the first drawing to handover: survey, design, planning, structural engineering, Building Regulations and the build itself.
Extensions and loft conversions
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Side Return Extension
£45k–£140k Fill in the alleyway beside your Victorian or Edwardian terrace and gain 10 to 18 square metres of kitchen, without losing the garden. Designed and built… Costs, planning and projects → -
Rear Extension
£40k–£150k Push the back of the house out into the garden for a full-width kitchen-diner or living room. One team for design, planning and build, with the… Costs, planning and projects → -
Wraparound Extension
£70k–£250k Fill the side return and extend to the rear in one L-shaped build for the biggest possible ground floor. Designed, priced in writing and built by… Costs, planning and projects → -
Kitchen Extension
£40k–£180k A bigger, brighter kitchen-diner at the heart of the house, designed around how you cook and live. One team for the extension and the kitchen, with… Costs, planning and projects → -
Ground Floor Extension
£40k–£250k Side return, rear, or both: a ground floor extension that gives your London home the open-plan living space it was never built with. One team, priced… Costs, planning and projects → -
Loft Conversion
£60k–£150k Turn the roof space you already have into a bedroom and bathroom, without touching the garden. Velux, dormer, hip-to-gable or mansard, designed and built by one… Costs, planning and projects → -
Loft Extension
£80k–£220k When the roof you have isn't enough: raise it, rebuild it or add a full storey for the biggest possible top floor. One team designs it,… Costs, planning and projects →
Prices compared (October 2026)
| Service | Price | Best for |
|---|---|---|
| Side Return Extension | £45k–£140k | Fill in the alleyway beside your Victorian or Edwardian terrace and gain 10 to 18 square metres of… |
| Rear Extension | £40k–£150k | Push the back of the house out into the garden for a full-width kitchen-diner or living room |
| Wraparound Extension | £70k–£250k | Fill the side return and extend to the rear in one L-shaped build for the biggest possible ground… |
| Kitchen Extension | £40k–£180k | A bigger, brighter kitchen-diner at the heart of the house, designed around how you cook and live |
| Ground Floor Extension | £40k–£250k | Side return, rear, or both |
| Loft Conversion | £60k–£150k | Turn the roof space you already have into a bedroom and bathroom, without touching the garden |
| Loft Extension | £80k–£220k | When the roof you have isn't enough |
Each service page shows what its prices include. Every house is different: your written price follows the design phase. For a figure based on your own floor area, use the instant estimate.
Alongside your build
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Party Wall Surveyor
From £600 Party wall notices served for a fixed fee of £500 + VAT by our approved party wall surveyor, with support until your neighbours have replied. Read more → 3D Visualisation
See the layout, light and finishes before anything is built.Read more →Pre-Purchase Feasibility
Buying a house to extend? Find out what is realistic before you exchange.Read more →
Not sure which one you need?
Compare the ways to buildManage it yourself, build with our help, or design and build with us.
See what your council approvesApproved extensions and lofts, borough by borough.
Browse finished projectsFilter by borough, floor area and type.
Design bundles and feesWhat the design phase includes and costs.
Talk it through with an architectural designer
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