From £22,616
HOUSE BUILDING SERVICES LIMITED is a trusted extension builder serving customers in CM12 and the surrounding area. Contact us to today to get a com...
From £23,584
Propello is an established and experienced local extension builder in CM12. Please contact us for a free, no obligation quote and competitive rate...
From £21,880
Experienced extension builder ready to quote for your work. CIA Construction Limited is the best extension builder in CM12. No obligation free quot...
From £22,064
Hyde Building Ltd are here to help customers who need an Extension Builder in CM12. We offer a competitive rate to complete all your extension buil...
From £22,360
Need an Extension Builder in CM12? Ellis & James Builders Limited has been helping local clients (20 mile radius) with their extension buildering j...
From £22,008
Over 35 years experience
We are Gas Safe registered
We are Verified
We pride ourselves on great custom...
From £22,312
Local Boiler Plumbing & Heating Services is an established and experienced local extension builder in CM12. Please contact us for a free, no obliga...
From £22,184
Experienced extension builder ready to quote for your work. CC&D BUILDING LTD is the best extension builder in CM12. No obligation free quotes and ...
From £21,880
Member since August 2025
Reliable and experienced extension builders with competitive rates and good at keeping within budget. Happy to provide examples of extension builde...
From £22,424
Nouvell Decor is a trusted extension builder serving customers in CM12 and the surrounding area. Contact us to today to get a competitive quote for...

A flat roof extension ranges from the cheapest of £21,880 (CIA Construction Limited based in RM18) to the dearest of £23,584 (Propello based in E17), but these are just estimates. While they give you an idea of who will be better value, the best way to compare costs is to get real quotes.
Find out how much your flat roof extension will cost in CM12 by posting a job with HaMuch. We'll send it to extension builders in CM12.
| Location in UK | Hourly Rate | Daily Rate |
|---|---|---|
| Build A Flat Roof Extension near Billericay | £38 | £248 |
| Build A Flat Roof Extension near Brentwood | £39 | £255 |
| Build A Flat Roof Extension near Basildon | £39 | £251 |
| Build A Flat Roof Extension near Wickford | £39 | £255 |
| Build A Flat Roof Extension near Stanford-le-Hope | £40 | £254 |
| Build A Flat Roof Extension near Chelmsford | £38 | £258 |
| Build A Flat Roof Extension near Rayleigh | £39 | £252 |
| Build A Flat Roof Extension near Thundersley | £38 | £251 |
| Build A Flat Roof Extension near Thurrock | £41 | £260 |
| Build A Flat Roof Extension near Chafford Hundred | £41 | £261 |
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.

Underpin a building - £17,831

Two storey extension - £88,497

Build a timber frame extension - £26,331

Build a swimming pool - £81,331

Single storey extension - £61,624

Side return extension - £45,226

Install an RSJ - £2,531

Outbuilding - £10,331

Build a Mansard loft conversion - £52,331

Loft conversion - £36,855

Build a kitchen extension - £42,331

Hip to gable loft conversion - £42,331

Granny annexe - £87,331

Garden office - £10,331

Convert a Garage - £16,331

Garage - £18,831

Build a flat roof extension - £22,331

Build a dormer loft conversion - £42,331

Concrete foundations - £6,581

Convert a bungalow loft - £29,331

Convert a basement - £41,226