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From £23,200
Banga Decoration
Sebastian Banga
Member since August 2025
Banga decoration. Is Base in south London for number of year Banga decoration is a small company. Wich provide an excellent job to the custom...
Greens Gardening & Landscape Property Maintenance
John Mcdonagh
Watch our short video highlighting all our expertise and services here:
more than 10 y...
Glenn Miller Builders Limited
Glenn Miller
Relax... you have found a reliable extension builder in SE25. Glenn Miller Builders Limited is a friendly and reliable company based in SE25 who co...
Aviemore Building Contractors Ltd
Experienced extension builder ready to quote for your work. Aviemore Building Contractors Ltd is the best extension builder in SE25. No obligation ...
Oaksure Construction
Stuart Bogazzi
Working as a builder for over 20 years now.
Family run business
Can sort any problem out and help build your dreams.
Bhagtana & Co Construction
Experienced extension builder ready to quote for your work. Bhagtana & Co Construction is the best extension builder in SE25. No obligation free qu...
K S BUILDERS (UK) LTD
Trusted and professional extension builder in SE25. Experienced in all extension buildering work and keeping within budget and on quote. K S BUILDE...
VDL Construction Ltd
Need to find an Extension Builder near you for all your extension buildering work?
VDL Construction Ltd provides a local, trusted extension...
Top Builders
Experienced extension builder ready to quote for your work. Top Builders is the best extension builder in SE25. No obligation free quotes and many ...
Howland Building Services
Need to find an Extension Builder near you for all your extension buildering work?
Howland Building Services provides a local, trusted exte...
Flat roof extension cost in SE25
A flat roof extension ranges from the cheapest of £21,568 (Oaksure Construction based in CR0) to the dearest of £23,200 (Banga Decoration based in CR7), 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 SE25 by posting a job with HaMuch. We'll send it to extension builders in SE25.
- How much does a flat roof extension cost?
- Flat roof extension cost per m2
- Factors affecting the cost of flat roof extensions
- Advantages and disadvantages of flat roofs
- Which is cheaper: a flat roof or pitched roof?
- How long does a flat roof extension take?
- Do you need planning permission for a flat roof extension?
- How long does a flat roof last?
- Can you walk on a flat roof extension?
- What insulation do I need for a flat roof extension?
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Estimates for common extension builder jobs in SE25;
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 - £17,774
Two storey extension - £88,412
Build a timber frame extension - £26,274
Build a swimming pool - £81,274
Single storey extension - £60,488
Side return extension - £44,587
Install an RSJ - £2,474
Outbuilding - £10,274
Build a Mansard loft conversion - £52,274
Loft conversion - £36,323
Build a kitchen extension - £42,274
Hip to gable loft conversion - £42,274
Granny annexe - £87,274
Garden office - £10,274
Convert a Garage - £16,274
Garage - £18,774
Build a flat roof extension - £22,274
Build a dormer loft conversion - £42,274
Concrete foundations - £6,524
Convert a bungalow loft - £29,274
Convert a basement - £40,587