Name: Extension Builder
Brand: HaMuch
SKU: extension-renovation
Rating: 4.71 (7 reviews)

Find affordable SE12 extension builders

Prices range from cheapest £15/hour and £13/day (TDR Property Maintenance ) to £46/hour and £288/day (Altash Building Services) - average £40/hr and £249/day

HaMuch is Excellent

Local SE12 extension builders, reviews & latest jobs

"Convert a Garage" - SE13, job posted 14/09/26

"1st floor Timber frame extension 28m2" - SE9, job posted 15/04/26

"Dormer loft conversion" - SE3, job posted 30/08/25

"Dormer loft conversion" - SE9, job posted 24/02/25

"RSJ installation - check if we need one installed" - ELTHAM, job posted 06/01/25

"Outbuilding Foundations is already done of concrete, Need a quote with brick work. Need a quote only wood work" - BR1, job posted 13/06/24

"Loft conversion" - SE3, job posted 18/03/24

Quickly find an Extension Builder in SE12

Use these steps to find Extension Builders in SE12 for FREE!

Post your job: Click "Get quotes" and briefly describe your job.
Enter your details: We’ll match you with Extension Builders in SE12. 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 SE12 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 Grove Park
Extension Builders in Eltham
Extension Builders in Blackheath
Extension Builders in Catford
Extension Builders in Lewisham
Extension Builders in Bromley
Extension Builders in Brockley
Extension Builders in Charlton
Extension Builders in Greenwich
Extension Builders in Chislehurst

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 - £26,096

Garden office - £10,096

Granny annexe - £87,096

Build a flat roof extension - £22,096

Convert a Garage - £16,096

Hip to gable loft conversion - £42,096

Convert a bungalow loft - £29,096

Build a dormer loft conversion - £42,096

Build a swimming pool - £81,096

Build a Mansard loft conversion - £52,096

Concrete foundations - £6,346

Underpin a building - £17,596

Two storey extension - £88,144

Convert a basement - £38,580

Side return extension - £42,580

Loft conversion - £34,650

Garage - £18,596

Single storey extension - £56,920

Outbuilding - £10,096

Install an RSJ - £2,296

Build a kitchen extension - £42,096

More extensions & conversions cost guides...

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