Name: Extension Builder
Brand: HaMuch
SKU: extension-renovation
Rating: 4.75 (4 reviews)

Find affordable SE21 extension builders

Prices range from cheapest £37/hour and £235/day (Claudiu Mihaila) to £62/hour and £378/day (RCB Group Design & Build) - average £43/hr and £273/day

HaMuch is Excellent

Local SE21 extension builders & latest jobs

"To divide a room" - SW2, job posted 08/07/25

"Two storey extension" - HERNE HILL, job posted 12/01/25

"Side return extension" - SE26, job posted 04/08/24

"Reconstructed full House" - DULWICH, job posted 16/05/24

Quickly find an Extension Builder in SE21

Use these steps to find Extension Builders in SE21 for FREE!

Post your job: Click "Get quotes" and briefly describe your job.
Enter your details: We’ll match you with Extension Builders in SE21. We’ll notify you via text or email when an Extension Builder is available to quote.
Select your Extension Builder: Compare Extension Builders interested in working with you. You can use HaMuch to safely message local SE21 Extension Builders or phone them directly - you’re in control!

What are the best ways to avoid problems when paying the Extension Builder?

The most important thing is do avoid handing over cash or paying large sums in advance. Be wary of paying cash for a cheaper job, i.e. to avoid VAT, you may be going down a slippery slope of not doing things properly which may eventually mean your job is also not done properly.

Agree when you intend to pay, ideally after you are satisfied with the completed job. If it is a big job agree a schedule of staged payments which is fair to both parties.

To avoid bad tradespeople and to ensure you can find them should they not answer a mobile;

Get proper contact details and check them yourself
Check if the company is verified on the Companies House website
Get phone details, ideally a land line or 0800 number and check it
Get a physical office address

Before the job starts should I agree standards of quality and behaviour?

Get quotes in writing by email or in person if possible. Getting quotes online or by text is ok (make sure you accept the offer by replying). For large projects make a written agreement, schedule of works and snagging plans as part of a working document. Also;

Agree expected quality of workmanship and materials in advance
When will work start and when will project be finished, what happens if project over runs ?
How long is the guarantee on work and materials eg 12 months
Discuss onsite behaviour in advance (no smoking, swearing or using mobile phones for non-work purposes)
Agree that your Extension Builder will remove all debris and rubbish and what level of tidying up you want after job

Local Extension Builders in London Boroughs

Local Extension Builders in London Boroughs
Borough in London
Extension Builders in Dulwich
Extension Builders in Tulse Hill
Extension Builders in Herne Hill
Extension Builders in East Dulwich
Extension Builders in Crystal Palace
Extension Builders in Brixton
Extension Builders in Sydenham
Extension Builders in Forest Hill
Extension Builders in Streatham
Extension Builders in Penge

Job estimates from extension builders near you

Whether you’re looking to extend your kitchen with a side return extension or you want to convert your basement into a liveable space, read our cost guides to get an idea of how much each project costs before getting a more accurate quote from our database of reliable tradespeople.

Build a timber frame extension - £26,184

Garden office - £10,184

Granny annexe - £87,184

Build a flat roof extension - £22,184

Convert a Garage - £16,184

Hip to gable loft conversion - £42,184

Convert a bungalow loft - £29,184

Build a dormer loft conversion - £42,184

Build a swimming pool - £81,184

Build a Mansard loft conversion - £52,184

Concrete foundations - £6,434

Underpin a building - £17,684

Two storey extension - £88,276

Convert a basement - £39,570

Side return extension - £43,570

Loft conversion - £35,475

Garage - £18,684

Single storey extension - £58,680

Outbuilding - £10,184

Install an RSJ - £2,384

Build a kitchen extension - £42,184

More extensions & conversions cost guides...

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