Cardiff and the Vale
Rear extensions for detached houses in Cardiff and the Vale
Wider, deeper rear extensions with room for vaulted roofs and big glazing. We design and build rear extensions across Cardiff and the Vale, from Cardiff and Barry to Penarth, covering single-storey kitchen extensions, two-storey additions, side returns and wraparounds.
Older terraces near the centre and post-war semis further out are typical of Cardiff and the Vale. Sloping sites are common in Wales, so floor levels and retaining walls are designed at the start.
How much does a detached house rear extension cost in Cardiff and the Vale?
Guide prices for a detached house rear extension in Cardiff and the Vale start from our Wales rate of £1,810–£2,980 per square metre, including VAT. Prices in Wales sit below our West Midlands baseline; sloping sites are the main variable.
| Size | Guide price inc VAT |
|---|---|
| 4 m wide × 6 m deep (24 m²) | £43,500–£71,500 |
| 5 m wide × 8 m deep (40 m²) | £72,500–£119,000 |
Your written price follows a measured survey and an agreed design, so it reflects your house, not an average.
Do you need planning permission in Cardiff and the Vale?
In Wales a single-storey rear extension can often be permitted development if it projects no more than 4 metres beyond the rear wall and is no more than 4 metres high. Wales has no prior approval route for deeper extensions, so anything bigger needs a householder planning application.
Welsh rules allow a two-storey rear extension without an application only where the ground floor is no deeper than 4 metres, the upper floor no deeper than 3 metres and at least 10.5 metres remains to the rear boundary. Most homeowners still apply for householder planning permission.
Conservation areas, National Parks and National Landscapes restrict permitted development in Wales, and listed buildings need listed building consent.
Where in Cardiff and the Vale do we work?
FAQ
Questions people ask
Can I have a vaulted ceiling?
Yes, with a pitched roof and exposed or boxed rafters, subject to the height limits.
Is an oak frame worth it?
It is a premium finish with a long life; it costs more than blockwork with a plain roof.
Do I need party wall notices?
Only if the extension is close enough to a neighbour's building for the excavation rules to apply.
Do you cover all of Cardiff and the Vale?
We cover 6 towns and districts in Cardiff and the Vale, including Cardiff, Barry and Penarth.
Who builds the extension?
Vetted building teams working under contract to us; your contract is with S&K Property Investments and Improvement Ltd.