Name: Extension Builder
Brand: HaMuch
SKU: extension-renovation
Rating: 4.63 (8 reviews)

Find affordable Harrow extension builders

Prices range from cheapest £29/hour and £230/day (HONEST CONTRUCTION LIMITED) to £63/hour and £304/day (EUROCONTRACTOR LIMITED) - average £42/hr and £264/day

HaMuch is Excellent

Local Harrow extension builders, reviews & latest jobs

"Kitchen extension" - UB6, job posted 15/05/26

"Loft conversion" - HARROW, job posted 04/04/26

"Loft conversion" - HARROW ON THE HILL, job posted 29/09/25

"Garden office" - HARROW ON THE HILL, job posted 20/07/25

"Loft conversion" - HARROW ON THE HILL, job posted 05/07/25

"Loft conversion" - HARROW ON THE HILL, job posted 07/03/25

"Dormer loft conversion" - HARROW, job posted 14/08/24

"Loft conversion" - HARROW, job posted 09/08/24

Quickly find an Extension Builder in Harrow

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

Post your job: Click "Get quotes" and briefly describe your job.
Enter your details: We’ll match you with Extension Builders in Harrow. 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 Harrow 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 Harrow
Extension Builders in Rayners Lane
Extension Builders in Wealdstone
Extension Builders in Pinner
Extension Builders in Stanmore
Extension Builders in Sudbury
Extension Builders in Wembley
Extension Builders in Greenford
Extension Builders in Northolt
Extension Builders in Ruislip

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 - £26,168

Garden office - £10,168

Granny annexe - £87,168

Build a flat roof extension - £22,168

Convert a Garage - £16,168

Hip to gable loft conversion - £42,168

Convert a bungalow loft - £29,168

Build a dormer loft conversion - £42,168

Build a swimming pool - £81,168

Build a Mansard loft conversion - £52,168

Concrete foundations - £6,418

Underpin a building - £17,668

Two storey extension - £88,252

Convert a basement - £39,390

Side return extension - £43,390

Loft conversion - £35,325

Garage - £18,668

Single storey extension - £58,360

Outbuilding - £10,168

Install an RSJ - £2,368

Build a kitchen extension - £42,168

More extensions & conversions cost guides...

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