House Extension
in Thornbury
Compare quotes from vetted Thornbury extension builders for single-storey, double-storey and rear extensions. Transparent pricing from £15,000. Free, no-obligation quotes — results in 24 hours.
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How Much Do House Extension Cost in Thornbury?
Real prices from completed projects in Thornbury 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 →Thornbury pricing note: South West England (Bristol, Devon, Cornwall) varies significantly by location. Bristol prices sit near the national average; rural Devon and Cornwall can run 5–10% higher due to contractor travel costs and limited local trade availability. Prices shown are indicative ranges for Thornbury and South West. Always get at least 3 written quotes before committing to any builder.
House Extension Specialists Who Know Thornbury
Thornbury has a thriving home improvement market driven by a strong local economy and a mix of Victorian terraces, post-war housing and contemporary developments. Finding the right builder is key to any successful project.
Every builder in our Thornbury network is thoroughly vetted before joining BestBuilders. We verify insurance cover, check trade memberships with bodies such as the FMB and CIOB, and require a minimum of five real customer reviews.
From a small bathroom refurbishment to a major double-storey extension, our vetted Thornbury builders cover the full range of residential projects. Request your free quotes today and compare options before making any decisions.
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What Thornbury Homeowners Say About Our House Extension Specialists
Conservation-area sympathetic extension on our 1960s detached in Thornbury. Pitched roof with two large rooflights, ceiling fan to the apex. Final cost £70400 fully fitted out. Snagging fully resolved within 14 days of completion.
Compared four extension builders through BestBuilders for the Thornbury job. Final pick had a structural engineer on staff, not subcontracted. Permitted Development route confirmed via a Lawful Development Certificate before any digging. Came in at £54180 over 14 weeks, no surprise extras. Family of four lived in throughout - we managed.
Past a year and the extension is the most-used part of the whole house. Builder we found via BestBuilders in Thornbury specced higher-grade glazing than we asked for - winter heating bills are noticeably lower. Total £81720. Best decision we have made on this house.
House Extension in Thornbury — FAQs
Plan Your house extension Project in Thornbury
Whether you're researching costs, checking planning rules, or comparing approaches before you commit, our editorial team has produced these guides to help Thornbury 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 Thornbury
Before you compare quotes, it's worth understanding the full UK price picture for house extension and how Thornbury 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 Thornbury
Find out whether your house extension needs planning permission in Thornbury, 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.