From £22,392
Need an Extension Builder in SG12? Samuele Paolini has been helping local clients (5 mile radius) with their extension buildering jobs for many ye...
From £22,312
Local Boiler Plumbing & Heating Services is an established and experienced local extension builder in SG12. Please contact us for a free, no obliga...
From £21,920
NISUP BUILDING SERVICES Company specializes in the domestic and commercial building industry :1. Refurbishm...
From £22,432
Platinum Electrics is a Branch off Platinum Premier Projects who deal in all types of construction projects. Platinum Electrics are based in London...
From £22,184
Experienced extension builder ready to quote for your work. CC&D BUILDING LTD is the best extension builder in SG12. No obligation free quotes and ...
From £22,184
Relax... you have found a reliable extension builder in SG12. First guard Roofing is a friendly and reliable company based in SG12 who consider no ...
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 £22,248
At Building Services Contractors we pride ourselves on an efficient and friendly service, and strive to achieve 100% customer satisfaction.
From £23,584
Propello is an established and experienced local extension builder in SG12. Please contact us for a free, no obligation quote and competitive rate...
From £22,424
Nouvell Decor is a trusted extension builder serving customers in SG12 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 (Can design and Construction based in Ig11) 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 SG12 by posting a job with HaMuch. We'll send it to extension builders in SG12.
| Location in UK | Hourly Rate | Daily Rate |
|---|---|---|
| Build A Flat Roof Extension near Ware | £47 | £296 |
| Build A Flat Roof Extension near Hertford | £46 | £289 |
| Build A Flat Roof Extension near Hoddesdon | £46 | £296 |
| Build A Flat Roof Extension near East Hertfordshire | £44 | £289 |
| Build A Flat Roof Extension near Welwyn Garden City | £42 | £268 |
| Build A Flat Roof Extension near Cheshunt | £48 | £285 |
| Build A Flat Roof Extension near Harlow | £43 | £288 |
| Build A Flat Roof Extension near Hatfield | £64 | £283 |
| Build A Flat Roof Extension near Stevenage | £44 | £282 |
| Build A Flat Roof Extension near Potters Bar | £43 | £273 |
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 - £17,856

Two storey extension - £88,534

Build a timber frame extension - £26,356

Build a swimming pool - £81,356

Single storey extension - £62,120

Side return extension - £45,505

Install an RSJ - £2,556

Outbuilding - £10,356

Build a Mansard loft conversion - £52,356

Loft conversion - £37,088

Build a kitchen extension - £42,356

Hip to gable loft conversion - £42,356

Granny annexe - £87,356

Garden office - £10,356

Convert a Garage - £16,356

Garage - £18,856

Build a flat roof extension - £22,356

Build a dormer loft conversion - £42,356

Concrete foundations - £6,606

Convert a bungalow loft - £29,356

Convert a basement - £41,505