From £17,892
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 £17,812
Local Boiler Plumbing & Heating Services is an established and experienced local extension builder in SG12. Please contact us for a free, no obliga...
From £17,420
NISUP BUILDING SERVICES Company specializes in the domestic and commercial building industry :1. Refurbishm...
From £17,932
Platinum Electrics is a Branch off Platinum Premier Projects who deal in all types of construction projects. Platinum Electrics are based in London...
From £17,684
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 £17,684
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 £17,380
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 £17,748
At Building Services Contractors we pride ourselves on an efficient and friendly service, and strive to achieve 100% customer satisfaction.
From £19,084
Propello is an established and experienced local extension builder in SG12. Please contact us for a free, no obligation quote and competitive rate...
From £17,924
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...

Underpinning ranges from £17,380 (Can design and Construction based in Ig11) to £19,084 (Propello based in E17), but the final cost will depend on the method of underpinning used, how much of your foundations need underpinning and where you live.
Comparing extension builders estimates for underpinning gives you an idea of who will be better value but the best way to compare costs is to get actual quotes.
Get quotes to underpin your home in SG12 by posting a job with HaMuch and we will send it to extension builders in SG12.
| Location in UK | Hourly Rate | Daily Rate |
|---|---|---|
| Underpin A Building near Ware | £47 | £296 |
| Underpin A Building near Hertford | £46 | £289 |
| Underpin A Building near Hoddesdon | £46 | £296 |
| Underpin A Building near East Hertfordshire | £44 | £289 |
| Underpin A Building near Welwyn Garden City | £42 | £268 |
| Underpin A Building near Cheshunt | £48 | £285 |
| Underpin A Building near Harlow | £43 | £288 |
| Underpin A Building near Hatfield | £64 | £283 |
| Underpin A Building near Stevenage | £44 | £282 |
| Underpin A Building 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