House Extension
in Portsmouth
Compare quotes from vetted Portsmouth extension builders for single-storey, double-storey and rear extensions. Transparent pricing from £17,500. Free, no-obligation quotes — results in 24 hours.
- Vetted, insured house extension specialists in Portsmouth
- Up to 3 free quotes — compare and choose with no pressure
- Transparent pricing, no hidden costs or surprise charges
- Work guaranteed, fully insured, trade-qualified contractors
How Much Do House Extension Cost in Portsmouth?
Real prices from completed projects in Portsmouth 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 →Portsmouth pricing note: Southern England (Hampshire, Dorset, West Sussex) sits around 10–15% above the national average. Coastal locations and areas with restricted site access can attract additional charges from contractors. Prices shown are indicative ranges for Portsmouth and Southern. Always get at least 3 written quotes before committing to any builder.
House Extension Specialists Who Know Portsmouth
Portsmouth is one of the UK's most active home renovation markets. With a diverse range of properties across the area, from period homes to modern new builds, local builders need to be versatile, skilled, and reliable.
BestBuilders vets every builder in our Portsmouth network. We check for public liability insurance, relevant trade qualifications (CIOB, FMB, Gas Safe, NICEIC), and a minimum of five verified customer reviews before any builder can appear on our platform.
Whether you are planning a rear extension, a loft conversion, or a full kitchen renovation in Portsmouth, we will connect you with the right specialist within 24 hours. All quotes are free and there is no obligation to proceed.
Start My Free Quote →How It Works
Every Builder We Recommend Is:
What Portsmouth Homeowners Say About Our House Extension Specialists
Side-return infill extension on our 1960s detached in Portsmouth. 36m² split between dining space and a snug, with a window seat over the new radiators. Final cost £64000 fully fitted out. Party wall agreement handled by their consultant - smooth process.
Compared four extension builders through BestBuilders for the Portsmouth job. Two FMB-affiliated builders, two not. Went with the one whose references checked out best. Structural engineer report and party wall award all coordinated through one contact. £70000 all-in over 13 weeks. Daily 5pm site walk with the foreman, weekly progress on the spreadsheet.
Three years on, EPC went from D to B thanks to the spec they used. Builder we found via BestBuilders in Portsmouth pushed back on our paving choice and saved us £2k on something more durable. Total £66600. Insurance happy with the building control completion certificate.
House Extension in Portsmouth — FAQs
Plan Your house extension Project in Portsmouth
Whether you're researching costs, checking planning rules, or comparing approaches before you commit, our editorial team has produced these guides to help Portsmouth 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:
House Extension Near Portsmouth
We also connect homeowners with vetted house extension specialists in towns surrounding Portsmouth.
Planning Your House Extension in Portsmouth
Before you compare quotes, it's worth understanding the full UK price picture for house extension and how Portsmouth 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 Portsmouth
Find out whether your house extension needs planning permission in Portsmouth, 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.