Home Extension Builders in South East London and Kent
Rear, side return and double storey extensions, design to build
Buildaway designs and builds home extensions across South East London and Kent, including rear, side return, wrap around and double storey extensions. We take the whole job from the first drawings through groundwork, structure, roofing and fit out to a finished room. Every extension comes with a free site visit, a fixed written quote and an 18 month workmanship warranty, and we are registered with the Federation of Master Builders.
We manage the planning, party wall and building control side for you, and one team stays on site from the foundations to the final coat of paint. We agree the timeline and the price with you before we break ground.
Registered with the Federation of Master Builders, and every job we do is covered by our 18 month workmanship warranty.
What's Included
Full groundworks and structural build
Expert groundworks and structural construction services.
Plumbing, electrics, and heating integration
Professional installation of all mechanical and electrical systems.
Roofing, windows, and external finish
Complete roofing, window installation and exterior finishing.
Plastering, flooring, and decorating
Professional plastering, flooring and decorating services.
Interior fit-out and finishing
Complete interior fit-out and professional finishing touches.
Project management and schedule control
Professional project management and timeline control throughout.
Building regs & compliance support
Whether you've got plans in place or need help getting started, we'll guide you every step of the way.
Why Buildaway for Your Extension?
Everything managed under one roof
No juggling architects, builders, and trades, we handle the lot.
Premium finish, inside and out
From bricks to paintwork, we deliver extensions that blend in beautifully and last for years.
Planning, progress, peace of mind
You get updates, timelines, and straight answers, no surprises.
All work backed by our workmanship warranty
Plus, we're happy to liaise with planning and building control on your behalf.
Areas We Cover
We build extensions right across South East London and Kent. Below are some of the areas we work in most often. Choose your area for local details and recent work.
We work in many more areas across London and Kent. Visit our areas we cover page to check that we work at your postcode.
Get Your Free Quote
Tell us about your project and we will come back with a fixed written quote after a free site visit.
Common Questions
How much does an extension cost in London?
A single-storey rear extension in London typically costs between £30,000 and £60,000, while a double-storey extension ranges from £50,000 to £100,000 or more depending on the size, specification and site conditions. A small side-return infill of around eight to ten square metres usually starts from about £25,000. Costs are influenced by foundation depth, the complexity of the roof, whether you need steelwork to open up the back of the house, the quality of windows and doors, and the internal finish, plastering, electrics, plumbing, flooring and decoration. We visit the property, review any existing architectural drawings you have, discuss your requirements and then provide a fixed written quote that covers every stage from groundworks to handover. Planning fees, building regulations and structural engineering are itemised separately so you can see exactly where every pound is going.
Do I need planning permission for an extension?
Some extensions fall under permitted development and some need full planning permission. It depends on the size, your property and where you live. We check this at the site visit and handle any application for you.
How long does an extension take to build?
A single-storey rear extension usually takes between ten and fourteen weeks from breaking ground to final handover. A double-storey extension or a large wraparound typically takes fourteen to twenty weeks. The programme begins with groundworks and foundations, which take around two weeks depending on soil conditions. Brickwork and the roof follow over the next three to four weeks, then windows and doors are fitted to make the shell weathertight. Internal work, first-fix plumbing and electrics, insulation, plastering, screeding, second-fix services, kitchen or bathroom fitting, flooring and decoration, fills the remaining weeks. We agree a detailed timeline before starting and provide weekly progress updates. Weather and any unforeseen ground conditions can affect foundations, but we build contingency into the schedule. You will know the expected completion date before we start and we keep to it.
What about party wall agreements?
If your extension affects a shared wall or boundary, you may need a party wall agreement with your neighbours. We will tell you if one applies and guide you through the process.
Are you insured and is the work guaranteed?
Yes. We are registered with the Federation of Master Builders, we carry full public liability insurance and every extension is covered by an 18 month workmanship warranty.
Guides Worth Reading
Practical advice from our team on planning and costing your project.