Home extensions in Cardiff
We design and build house extensions for homes in Cardiff and the surrounding South Glamorgan area, with guide prices adjusted for the region.
- Postcode districtsCF5, CF10, CF11, CF14, CF23, CF24
- Price regionWales (×0.93)
- Planning rulesWales
- Site visitFree, no obligation
Cardiff extension prices at a glance
Prices on this page use our Wales factor of ×0.93, include VAT at 20% and cover the build; your written price follows a survey and agreed drawings.
| Extension type | Example size | Standard spec (inc VAT) |
|---|---|---|
| Single-storey rear extensions | 20 m² | £38,000 – £48,500 |
| Double-storey extensions | 32 m² | £53,500 – £70,000 |
| Wraparound extensions | 25 m² | £53,000 – £67,500 |
| Orangery extensions | 16 m² | £41,500 – £52,500 |
| Extensions over a garage | 12 m² | £23,000 – £30,500 |
| Conservatory replacement extensions | 14 m² | £27,500 – £36,000 |
Which extension suits a Cardiff home?
Welsh housing ranges from stone terraces in the valleys to render-and-slate houses and modern estates, and the Welsh planning rules differ from England's in several places.
The types we would usually look at first for a home in Cardiff are bungalow extensions, single-storey rear extensions and side return extensions, depending on the garden and how the house is laid out.
Planning rules in Cardiff
In Wales a single-storey rear extension can usually project up to 4 m beyond the rear wall without a planning application, if it is no more than 4 m high, keeps eaves to 3 m and overall height to 4 m within 2 m of a boundary, and covers no more than half the land around the original house. Wales has no larger home extension prior approval scheme.
In Wales a rear extension of more than one storey can be permitted development only if the ground floor projects no more than 4 m, the upper floor no more than 3 m, it stays at least 10.5 m from the rear boundary and it is not in a conservation area, national park, National Landscape or World Heritage Site. Anything larger needs a planning application to the council.
In a conservation area, national park, National Landscape or World Heritage Site the permitted development limits are tighter (no side or two-storey extensions without an application). Listed homes need listed building consent, and if permitted development rights have been removed, any extension needs an application.
The Party Wall etc. Act 1996 applies in Wales as in England: notice must be served before work to a shared wall, building on the boundary, or excavating close to a neighbour's foundations.
Applications are decided by the local planning authority (your county or county borough council, or the national park authority).
Choose an extension type
- Extension plans and drawings · from £1,100
- Planning permission for extensions · from £300
- Wraparound extensions · from £33,000
- Extensions over a garage · from £22,000
- Conservatory replacement extensions · from £18,500
- Annexe extensions · from £51,000
- Side return extensions · from £16,500
- Bungalow extensions · from £24,000
- Home office extensions · from £14,500
- Bedroom extensions · from £24,000
- Single-storey rear extensions · from £19,500
- Timber frame extensions · from £19,500
- Double-storey extensions · from £35,000
- Orangery extensions · from £27,500
- Building regulations for extensions · from £800
- Flat roof extensions · from £19,500
- Kitchen extensions · from £25,000
- Glass box extensions · from £27,500
- Porch extensions · from £3,700
- Utility and boot room extensions · from £13,000
- Pitched roof extensions · from £20,500
- Side extensions · from £20,000
Free site visit
It starts with a visit to your house to measure, check access and talk through ideas and budget.
Design and approvals
Once the layout is agreed, we deal with the council: planning permission or written confirmation that none is needed, plus building control.
Fixed written price
The price is fixed in writing once the design is settled, with a clear programme and payment stages.
Build and sign-off
The build is managed from start to finish, inspected at each stage and signed off on completion.
Questions about extensions in Cardiff
How much does an extension cost in Cardiff?
Using our Wales factor (×0.93), a standard-spec single-storey extension of 20 m² is a guide £38,000 to £48,500 including VAT, and a 32 m² two-storey extension £53,500 to £70,000. Your written price follows the survey.
Will my neighbours need to be told?
If you apply for planning the council notifies them, and in Wales party wall notices may be needed for work near a shared boundary.
Who do I contract with?
Your contract is with S&K Property Investments and Improvement Ltd, which designs and manages the project and the build teams who carry it out.
How long does an extension take in Cardiff?
Usually 2 to 4 months of design and approvals, then 10 to 16 weeks on site for a single-storey extension or 16 to 24 weeks for two storeys.
Book a free site visit in Cardiff
We will measure up, check the planning position and give you honest guide figures.
- Free, no-obligation site visit
- Planning route checked before you spend on drawings
- Written price once the design is agreed
- Building control sign-off at the end
Prefer to talk? Call 0800 088 6341 or .
Book a free site visit
Tell us a little about the project and we will arrange a time.