Derbyshire
Flat-roof rear extensions in Derbyshire
Warm flat roofs with lanterns, parapets and long-life membranes. We design and build rear extensions across Derbyshire, from Derby and Chesterfield to High Peak, covering single-storey kitchen extensions, two-storey additions, side returns and wraparounds.
Flat roofs are the usual choice for rear extensions because they stay below first-floor windows and take a lantern neatly. Derbyshire has plenty of inter-war semis and bungalows, and single-storey rear extensions suit both.
How much does a flat-roof rear extension cost in Derbyshire?
For Derbyshire we work from the East Midlands rate: £1,840–£3,010 per square metre of new floor, including VAT, standard specification. East Midlands prices sit a little below our West Midlands baseline.
| Size | Guide price inc VAT |
|---|---|
| 3 m wide × 4 m deep (12 m²) | £22,000–£36,000 |
| 4 m wide × 5 m deep (20 m²) | £37,000–£60,000 |
| 4 m wide × 6 m deep (24 m²) | £44,000–£72,000 |
Ground conditions, glazing, the roof and how far the house is opened up move the final figure within the range.
Do you need planning permission in Derbyshire?
In England a single-storey rear extension can often be built under permitted development: up to 3 metres beyond the original rear wall of an attached house, or 4 metres on a detached house, no higher than 4 metres, with eaves no higher than 3 metres if any part is within 2 metres of a boundary.
New fabric must meet Approved Document L (2021 edition incorporating 2023 amendments): walls 0.18, roof 0.15 and floor 0.18 W/m²K, windows 1.4 W/m²K or Band B. Under the simple route, new windows, doors and rooflights should not exceed 25% of the extension floor area plus any openings removed; more glass is possible with a whole-house calculation.
Conservation areas, National Parks, National Landscapes and the Broads restrict permitted development, and listed buildings always need listed building consent.
Where in Derbyshire do we work?
FAQ
Questions people ask
How long does a flat roof last?
A well-built single-ply or GRP warm roof typically lasts 25 years or more.
Is a flat roof really flat?
No; it is built to falls so water drains to outlets or gutters.
Can I walk on it?
Not as a balcony without planning permission and a guarding design; it can be accessed for maintenance.
Do you cover all of Derbyshire?
We cover 22 towns and districts in Derbyshire, including Derby, Chesterfield and High Peak.
Who builds the extension?
Vetted building teams working under contract to us; your contract is with S&K Property Investments and Improvement Ltd.