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

Find affordable N21 extension builders

Prices range from cheapest £36/hour and £238/day (Acacia Gardens Ltd) to £50/hour and £313/day (CESV Ltd) - average £44/hr and £275/day

HaMuch is Excellent

Local N21 extension builders, reviews & latest jobs

"Underpinning" - EN2, job posted 19/12/25

"Rear dormer loft extension to provide 2 bedrooms and 1 shower room on a semi-detached property in Enfield." - EN2, job posted 15/07/25

"Rear dormer loft extension to provide 2 bedrooms and 1 shower room on a semi-detached property in Enfield" - EN2, job posted 15/07/25

"Loft extension and ground floor extension" - EN2, job posted 04/12/23

Quickly find an Extension Builder in N21

Use these steps to find Extension Builders in N21 for FREE!

Post your job: Click "Get quotes" and briefly describe your job.
Enter your details: We’ll match you with Extension Builders in N21. 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 N21 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 Winchmore Hill
Extension Builders in Palmers Green
Extension Builders in Southgate
Extension Builders in Botany Bay
Extension Builders in Enfield
Extension Builders in Edmonton
Extension Builders in Upper Edmonton
Extension Builders in Friern Barnet
Extension Builders in Wood Green
Extension Builders in Cockfosters

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 - £26,160

Garden office - £10,160

Granny annexe - £87,160

Build a flat roof extension - £22,160

Convert a Garage - £16,160

Hip to gable loft conversion - £42,160

Convert a bungalow loft - £29,160

Build a dormer loft conversion - £42,160

Build a swimming pool - £81,160

Build a Mansard loft conversion - £52,160

Concrete foundations - £6,410

Underpin a building - £17,660

Two storey extension - £88,240

Convert a basement - £39,300

Side return extension - £43,300

Loft conversion - £35,250

Garage - £18,660

Single storey extension - £58,200

Outbuilding - £10,160

Install an RSJ - £2,360

Build a kitchen extension - £42,160

More extensions & conversions cost guides...

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