House Extension
in Cardiff
Compare quotes from vetted Cardiff extension builders for single-storey, double-storey and rear extensions. Transparent pricing from £14,500. Free, no-obligation quotes — results in 24 hours.
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How Much Do House Extension Cost in Cardiff?
Real prices from completed projects in Cardiff and the surrounding area. Costs vary by size, specification and access — use these as a starting guide, then get 3 free quotes for your specific project.
The most popular choice for UK terraces and semis. Adds a kitchen-diner or extra living space at ground level. Typically 3–5m deep, completed in 10–14 weeks.
Get quotes for this →Maximum space gain in a single build — adds a ground-floor room and a bedroom above. Strong ROI in most UK property markets. Requires full planning permission.
Get quotes for this →Ideal for terraced homes with a narrow side alley. Transforms a cramped kitchen into a full-width open-plan space. Often combined with a rear extension.
Get quotes for this →Costs depend on size, spec and access. The best way to know your exact price is to compare 3 quotes from vetted local specialists.
Get free quotes →Cardiff pricing note: South Wales building costs run 10–15% below the national average, making it one of the most affordable regions in the UK for home improvements. Cardiff and Newport are well-served by vetted local contractors. Prices shown are indicative ranges for Cardiff and South Wales. Always get at least 3 written quotes before committing to any builder.
House Extension Specialists Who Know Cardiff
Home renovation activity in Cardiff continues to grow year on year. The area's varied housing stock, from older stone-built properties to new-build estates, means there is always strong demand for skilled, experienced local builders.
Before any builder appears on our Cardiff platform, we carry out a full vetting check covering public liability insurance, trade qualifications, company registration and verified customer feedback. Only builders who pass every stage are listed.
Our Cardiff builder network covers extensions, loft conversions, kitchens, bathrooms, roofing, driveways and more. Get up to 3 free, no-obligation quotes within 24 hours and choose the builder that best fits your project and budget.
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What Cardiff Homeowners Say About Our House Extension Specialists
Wraparound extension on our 1930s semi in Cardiff. Added 28m² of open-plan kitchen-diner with bi-fold doors and a roof lantern. Total £38700 across 12 weeks on site. Building control sign-off on the first inspection.
Compared four extension builders through BestBuilders for the Cardiff job. Highest-priced quote actually had the cheapest spec - the breakdown made it obvious. Architect drawings submitted by them, planning consent in 8 weeks. Final invoice £56760 - within 2% of the original quote. Lived in throughout - dust kept to the construction zone, never the rest of the house.
A year in, the underfloor heating runs the new space at zero heating cost from solar. Builder we found via BestBuilders in Cardiff recommended a roof lantern over a flat roof - genuinely transforms the light. Total £54840. Estate agent valued the work at +£90k.
House Extension in Cardiff — FAQs
Plan Your house extension Project in Cardiff
Whether you're researching costs, checking planning rules, or comparing approaches before you commit, our editorial team has produced these guides to help Cardiff homeowners make informed decisions about their house extension project.
House Extension Cost Guide
Detailed UK price ranges, regional adjustments and worked examples for house extension projects.
Read House Extension Cost Guide →All House Extension Specialists
Browse our nationwide network of vetted house extension contractors covering all 519 UK towns.
Browse House Extension Specialists →All Cost Guides
Compare prices across extensions, lofts, kitchens, bathrooms, roofing, driveways and solar projects.
View All Cost Guides →Planning your house extension project? Read these guides:
Planning Your House Extension in Cardiff
Before you compare quotes, it's worth understanding the full UK price picture for house extension and how Cardiff sits within it. The guides below cover average costs, what affects your quote, and how to choose a builder you can trust.
UK House Extension Cost Guide
Full price ranges, worked examples and the factors that move your quote — drawn from real project data across 519 UK towns.
Read the house extension cost guide →House Extension Across the UK
Browse house extension services nationwide, see what's typical in your region, and request quotes from any UK location.
Visit the UK house extension hub →Planning Permission for House Extension in Cardiff
Find out whether your house extension needs planning permission in Cardiff, what Permitted Development limits apply, and how rules differ in conservation areas, Article 4 zones, and listed-building settings.
Read the house extension planning rules →More homeowner resources: all UK building guides, cost guides, planning permission, comparisons, how-to guides and industry insights.