House Extension
in Chelmsford
Compare quotes from vetted Chelmsford 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 Chelmsford
- 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 Chelmsford?
Real prices from completed projects in Chelmsford 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 →Chelmsford pricing note: Eastern England (Essex, Hertfordshire, Cambridgeshire, Suffolk, Norfolk) runs approximately 8–12% above the national average, influenced by proximity to London and strong demand in commuter towns. Prices shown are indicative ranges for Chelmsford and Eastern. Always get at least 3 written quotes before committing to any builder.
House Extension Specialists Who Know Chelmsford
Chelmsford 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 Chelmsford 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 Chelmsford, 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 Chelmsford Homeowners Say About Our House Extension Specialists
Single-storey rear extension on our 1970s detached in Chelmsford. Underfloor heating zoned separately from the rest of the house, A-rated boiler upgraded. Job done for £85500 over 16 weeks. CCTV drain survey done before any digging started, no surprises later.
Compared four extension builders through BestBuilders for the Chelmsford job. Quotes ranged from £42k to £71k - went with the £58k mid-tier on detail. Trade plates on the kerb so the council parking team did not bother them. Came in at £86530 fitted including site clean and hand-back. Already booking them for the loft conversion next.
Two years post-completion the extension still feels like part of the original house. Builder we found via BestBuilders in Chelmsford argued for thicker insulation in the slab - heating bills are visibly lower year-round. Total £58620. Working from home is so much better with the new dedicated space.
House Extension in Chelmsford — FAQs
Plan Your house extension Project in Chelmsford
Whether you're researching costs, checking planning rules, or comparing approaches before you commit, our editorial team has produced these guides to help Chelmsford 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 Chelmsford
We also connect homeowners with vetted house extension specialists in towns surrounding Chelmsford.
Planning Your House Extension in Chelmsford
Before you compare quotes, it's worth understanding the full UK price picture for house extension and how Chelmsford 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 Chelmsford
Find out whether your house extension needs planning permission in Chelmsford, 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.