The 10 extension builders from Google's results for Cardiff, ranked on Google rating, online presence and other factors. Updated 10 September 2026.
Wales has run its own planning system since 2016 and permitted development rights differ from England.
on GoogleCardiff
Orange Stone Construction Ltd builds house extensions for homes in Cardiff. Its projects create extra rooms for larger families and open up living areas into wider open-plan spaces, with the team involved from the first consultation until the build is finished.
on GoogleCardiff
Rise Construction Cardiff Ltd constructs modern house extensions for residential properties in Cardiff and South Wales. The business carries out structural building work to expand home living areas.
029 2002 5944 Unit 8A Mill Farm Industrial Est, Cardiff CF14 0SH
on GoogleCardiff
Cjames Construction carries out domestic and commercial building projects throughout the Cardiff region. The company constructs house extensions, new builds and loft conversions alongside general home renovations.
on GoogleCardiff
Darkin Architects designs house extensions and residential renovations in Cardiff, Llanelli, and Neath. The firm creates plans and provides advice regarding planning permission and building regulations for home additions.
029 2274 4005 143 Clifton St, Cardiff CF24 1LZ
on GoogleCardiff
TDArchitect provides design and construction services for single-storey extensions, two-storey additions, loft conversions, and internal remodelling. The firm assists homeowners across Cardiff and South Wales with site assessments and custom drawings.
07971 277493 19 Conybeare Rd, Cardiff CF5 1GB
on GoogleCardiff
AJW Construction provides domestic building work, property renovations, and extensions in Cardiff.
029 2022 1823 40A Richards St, Cardiff CF24 4DA
on GoogleCardiff
For Ty Builders provides residential construction services across Cardiff and nearby communities. The firm handles whole-project management for new builds, property renovations, home extensions, and loft conversions.
07817 269005 12 Celyn Grove, Cardiff CF23 6SH
on GoogleLlanrumney, Cardiff
RGB Construction undertakes various building projects in Cardiff, including bathroom fitting, kitchen installations, extensions, and loft conversions. Work covers dormer, Velux, mansard, and hip-to-gable conversions for local properties.
07946 452571 11 Watchet Cl, Llanrumney, Cardiff CF3 4DU
on GooglePyle, Bridgend
Dunraven Windows builds glazed extensions across Bridgend, Swansea, Cardiff, Newport, Carmarthen, Bristol, and Gloucester.
0800 975 9222 Heol Mostyn Village Farm Industrial Estate St David’s House, Pyle, Bridgend CF33 6BJ
Cardiff
Eco Build Extensions constructs offsite modular home additions for clients in Coventry, assembling structures on site within days. Their work includes kitchen extensions, garage conversions, conservatory updates, and multi-storey residential builds.
In Cardiff, single storey, per m² typically costs £1,700 – £2,400. Labour in Cardiff runs 6% below the UK median, which accounts for most of the difference from the same job elsewhere.
These are the firms from Google's results for "house extensions cardiff". They are ranked on Google rating, online presence and other factors.
The figures above are Cardiff ranges. These explain what drives them, so you can read a quote properly.
Per-square-metre prices for single-storey, two-storey, side return and kitchen extensions, costs by size, the fees outside the build price, and planning limits by nation.
The permitted development limits for extensions, lofts, porches and outbuildings in England, where the rights do not apply, what prior approval and a certificate cost, and how Wales, Scotland and NI differ.
When the Party Wall Act applies, which notice to serve and how far ahead, what your neighbour can do, what a surveyor's award costs, and the rules in Scotland and NI.
Under permitted development, three metres for a terrace or semi and four for a detached, doubled to six and eight under the prior approval process. Height, materials and how much garden you cover all carry separate limits, and none of it applies in a conservation area.
If you are excavating within three metres of a neighbour's foundations or building on the boundary, yes. You must serve notice two months before work starts. Skipping it is the most common reason extension projects stall.