Name: Extension Builder
Brand: HaMuch
SKU: extension-renovation
Rating: 4.75 (2 reviews)

Find affordable N20 extension builders

Prices range from cheapest £21/hour and £165/day (Onyx Iv) to £77/hour and £323/day (Homeworks Design & Build Ltd) - average £46/hr and £273/day

HaMuch is Excellent

Local N20 extension builders & latest jobs

"Underpinning" - N20, job posted 01/03/26

"Loft conversion" - N20, job posted 11/01/24

Quickly find an Extension Builder in N20

Use these steps to find Extension Builders in N20 for FREE!

Post your job: Click "Get quotes" and briefly describe your job.
Enter your details: We’ll match you with Extension Builders in N20. 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 N20 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 Whetstone
Extension Builders in North Finchley
Extension Builders in Cockfosters
Extension Builders in High Barnet
Extension Builders in Friern Barnet
Extension Builders in Southgate
Extension Builders in Finchley
Extension Builders in Hampstead
Extension Builders in Muswell Hill
Extension Builders in Mill Hill

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 - £26,200

Garden office - £10,200

Granny annexe - £87,200

Build a flat roof extension - £22,200

Convert a Garage - £16,200

Hip to gable loft conversion - £42,200

Convert a bungalow loft - £29,200

Build a dormer loft conversion - £42,200

Build a swimming pool - £81,200

Build a Mansard loft conversion - £52,200

Concrete foundations - £6,450

Underpin a building - £17,700

Two storey extension - £88,300

Convert a basement - £39,750

Side return extension - £43,750

Loft conversion - £35,625

Garage - £18,700

Single storey extension - £59,000

Outbuilding - £10,200

Install an RSJ - £2,400

Build a kitchen extension - £42,200

More extensions & conversions cost guides...

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