Name: Extension Builder
Brand: HaMuch
SKU: extension-renovation
Rating: 4.8 (10 reviews)

Find local affordable WD18 extension builders

Cheapest £38/hour & £239/day (Progressive Design London) to £60/hour & £595/day (Design & Build Builders Ltd) - average £46/hour & £299/day

Sort by rates or availability

"Loft conversion" - WD19, job posted 07/05/26

"Looking for a loft conversion with a flat shed dormer (1 bed and bathroom) i have plans which have been submitted so looking for quotes" - WD24, job posted 26/12/25

"Loft conversion" - WD24, job posted 07/12/25

"Side return extension" - WD18, job posted 09/10/25

"I am looking for quotes for a small rear extension on a terraced property in WD18, Watford. The extension will be built directly behind the existing kitchen and will house a toilet, stand-up shower, and a small hand basin. Existing Details: Existing Kitchen Width (internal): 2.01 metres ..." - WD18, job posted 07/08/25

"I am looking for quotes for a small rear extension on a terraced property in WD18, Watford. The extension will be built directly behind the existing kitchen and will house a toilet, stand-up shower, and a small hand basin. Existing Details: Property Type: Mid-terrace house Location: WD18,..." - WATFORD, job posted 07/08/25

"Single storey extension" - WATFORD, job posted 26/05/25

"Loft conversion" - WD17, job posted 27/12/24

"Two storey extension" - WATFORD, job posted 16/12/24

"Side return extension" - WD17, job posted 05/03/24

Quickly find an Extension Builder in WD18

Use these steps to find Extension Builders in WD18 for FREE!

Post your job: Click "Get quotes" and briefly describe your job.
Enter your details: We’ll match you with Extension Builders in WD18. 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 WD18 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 West Watford
Extension Builders in Watford
Extension Builders in Watford
Extension Builders in Oxhey
Extension Builders in North Watford
Extension Builders in Potters Bar
Extension Builders in Bushey Heath
Extension Builders in Northwood
Extension Builders in Garston
Extension Builders in Rickmansworth

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 - £26,392

Garden office - £10,392

Granny annexe - £87,392

Build a flat roof extension - £22,392

Convert a Garage - £16,392

Hip to gable loft conversion - £42,392

Convert a bungalow loft - £29,392

Build a dormer loft conversion - £42,392

Build a swimming pool - £81,392

Build a Mansard loft conversion - £52,392

Concrete foundations - £6,642

Underpin a building - £17,892

Two storey extension - £88,588

Convert a basement - £41,910

Side return extension - £45,910

Loft conversion - £37,425

Garage - £18,892

Single storey extension - £62,840

Outbuilding - £10,392

Install an RSJ - £2,592

Build a kitchen extension - £42,392

More extensions & conversions cost guides...

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