Basildon · House Extension

House Extension
in Basildon

Compare quotes from vetted Basildon extension builders for single-storey, double-storey and rear extensions. Transparent pricing from £17,500. Free, no-obligation quotes — results in 24 hours.

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Basildon House Extension Prices

How Much Do House Extension Cost in Basildon?

Real prices from completed projects in Basildon 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.

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Single-storey extension
Rear or Side-Return Extension
£ 27,000 – £54,000

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.

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Double-storey extension
Full Double-Storey Rear Extension
£ 54,000 – £97,000

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.

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Side Extension
Side-Return or Infill Extension
£ 17,500 – £40,500

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.

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Costs depend on size, spec and access. The best way to know your exact price is to compare 3 quotes from local specialists.

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Basildon 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 Basildon and Eastern. Always get at least 3 written quotes before committing to any builder.

Why BestBuilders for House Extension in Basildon

House Extension Specialists Who Know Basildon

Tell us about your house extension project once and up to three local specialists who cover Basildon get in touch with quotes — free, with no obligation, and you choose who to hire.

Trades covering Basildon normally work across the surrounding area as well — including Romford, Luton and Kings Lynn — so your shortlist is drawn from the wider Eastern pool rather than a single postcode.

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. That regional context is worth holding in mind when you compare the quotes that come back for your Basildon job.

Local facts: Basildon

  • Local planning authority: Basildon Council (Essex)
  • Region: East of England
  • Town-centre postcode district: SS15
  • Average house price (Basildon local authority, June 2026): £360,294 (-1.0% year on year) — detached £663,580, semi-detached £420,370, terraced £313,485, flats £185,783

Planning-authority, region and postcode data: ONS Postcode Directory (Open Government Licence). House prices: HM Land Registry UK House Price Index for the local authority (OGL). Member coverage is each member's own registered base and travel radius.

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Frequently Asked Questions

House Extension in Basildon — FAQs

Single-storey extensions in Basildon typically run £2,000 to £3,000 per square metre, so a 20 square metre rear extension usually costs £40,000 to £60,000. Two-storey extensions cost more in total but less per square metre because the roof and foundations are shared.
Many single-storey rear extensions in Basildon fall under permitted development, up to 3 metres for an attached house or 4 metres for a detached one, or up to 6 and 8 metres under the larger home extension prior approval scheme. Conservation areas, listed buildings and most side extensions need full planning permission, so check with your builder first.
A single-storey extension usually takes 10 to 16 weeks on site, and a two-storey extension 16 to 24 weeks, weather and access permitting. Allow time for design, planning and building regulations approval before work begins in Basildon.
If your extension is built up to or astride a shared boundary, or involves digging near the foundations of a neighbouring property, the Party Wall Act applies and you must serve notice. Most Basildon builders flag this early so a party wall surveyor can be arranged in good time.
Yes, almost all extensions need building regulations approval covering structure, insulation, drainage and fire safety, even when planning permission is not required. Your Basildon builder works to these standards and arranges building control inspections at each key stage.
More House Extension Resources

Plan Your house extension Project in Basildon

Whether you're researching costs, checking planning rules, or comparing approaches before you commit, our editorial team has produced these guides to help Basildon 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.

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All House Extension Specialists

Browse our nationwide network of local house extension contractors covering all 519 UK towns.

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All Cost Guides

Compare prices across extensions, lofts, kitchens, bathrooms, roofing, driveways and solar projects.

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Planning your house extension project? Read these guides:

💷 Cost Guides 📋 Planning Permission ⚖️ Compare Builders 🛠 How-To Guides 📊 Industry Insights 🏛 UK Planning Rules 📚 All Guides
About This Page

Editorial standards & how to reach us

This House Extension in Basildon page is maintained by the BestBuilders Editorial Team. We vet the house extension specialists in our network but do not check insurance or qualifications. Ask any of them for their public liability certificate, their trade-body membership number (check it on that body’s own register) and two recent local jobs you can go and see. The cost ranges shown are cross-referenced against RICS BCIS regional data and itemised quotes flowing through the BestBuilders platform each month. For a full cost breakdown see our House Extension cost guide. FAQ content is reviewed quarterly.

Spotted something out of date? If a listed house extension specialist has moved on, a cost range looks wrong for Basildon, or you've had a poor experience with a contractor we recommended — we want to know. Email info@bestbuilders.co.uk or call 0800 852 7782. Every report is investigated and accepted corrections typically go live within 48 hours.

BestBuilders Editorial Team
UK-based · Reviewed 20 April 2026
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Helpful Resources

Planning Your House Extension in Basildon

Before you compare quotes, it's worth understanding the full UK price picture for house extension and how Basildon 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 Basildon

Find out whether your house extension needs planning permission in Basildon, 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.

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🏛️Planning permission for House Extension in Basildon?Check whether your project needs permission before you start — read our 2026 planning guide →
Maintained by the BestBuilders Editorial Team
House Extension cost data for Basildon checked by our UK editorial team. Credentials, cost data & FAQs reviewed quarterly.Reviewed by the BestBuilders editorial team · Last updated: 22 August 2026. How we research & fact-check
✉ info@bestbuilders.co.uk
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