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Extension Cost Calculator

Want to See How Much Your Extension Will Cost?

Extension Cost Calculator
Get an instant estimate for your home extension project
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Location
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Type
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Size
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Results
Where is your property?
Location significantly affects build costs due to labour rates and material supply.
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Bristol
City of Bristol
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Bath & NE Somerset
Bath and North East Somerset
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South Gloucestershire
Filton, Yate, Thornbury & more
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North Somerset
Weston-super-Mare, Clevedon & more
What type of project?
Each project type has different structural requirements that affect the overall cost.
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Single Storey
Rear ground-floor extension
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Double Storey
Two-level, ground and first floor
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Loft Conversion
Convert existing roof space into living space
What size extension?
Drag the slider to set your approximate floor area.
50m²
Approximate floor area
10 m² 50 m² 100 m² 150 m² 200 m²
Estimated Build & Labour Cost
£0 – £0
Based on your selections
Estimated Build & Labour Cost
Get your accurate figure
Need Help With the Rest of the Project?
The build cost above is a starting point. Every project also needs design drawings, structural engineering sign-off, building control approval, and — depending on the works — planning permission. We can provide the design services and help you understand what else your project will need and what it's likely to cost.
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Email us
info@adaptplanning.co.uk
We respond within 1 working day
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Call us
07850 937112
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No obligation — just a conversation about your project.

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Permitted Development

Avoid the need for full planning permission. We are experts on Permitted development. See if your project qualifies

Planning Applications

Get expert guidance on planning applications. With decades of experience in planning departments, trust us to secure the permissions you need

Instantly Estimate Your Extension Costs with Our Tool

Planning a home extension in Bristol or the surrounding areas? Our extension cost calculator is designed to give you instant, accurate estimates tailored to your needs. No guesswork, no complicated math—just clear and actionable insights to help you budget for your dream project.

Whether you’re considering a single-storey extension, a loft conversion, or a large-scale renovation, our calculator takes into account the key factors that influence costs in the different regions of the UK, including material prices, labour rates, and local planning requirements.

What’s Included in Your Estimate?

  •  When you use our calculator, you’ll get a detailed breakdown of expected costs, covering
  • What’s not included? Certain bespoke elements like custom furniture, luxury fixtures, or unexpected groundworks may need separate calculations.
  • Why does this matter? By knowing what’s included, you can plan your budget with confidence and avoid surprises during the build.

Materials

From standard bricks and tiles to premium finishes like timber cladding or skylights.

Labour Costs

Estimates for contractors, specialist trades, and general builders, based on typical rates in in your choosen region

Additional Costs

Includes potential expenses like planning application fees, building regulation checks, and VAT.

Factors That Impact Extension Costs

Size and Layout
Larger extensions don’t always mean higher costs. A compact design can often be more efficient. Multi-storey extensions can provide better value for money by maximising space without doubling groundwork expenses.
Materials
Budget options: Standard bricks, concrete, and basic fixtures. Premium upgrades: Sustainable timber, bi-fold doors, or natural stone.
Labour Costs
Expect variation based on the type of contractor (e.g., specialists vs. general builders) and location. Bristol and surrounding towns like Bath or Weston-super-Mare might have slightly different rates.
Planning Permission & Fees
In some cases, extensions fall under permitted development rights. Our tool highlights when planning permission might be needed and estimates associated costs.
Special Features
Skylights, underfloor heating, or eco-friendly systems (e.g. solar panels) can enhance your space but may also increase costs.

How to Save Money on Your Extension

Creating your dream extension doesn’t have to break the bank. With smart planning and the right choices, you can achieve a beautiful and functional space within your budget.

Use Cost-Effective Materials

Opt for budget-friendly materials like engineered wood instead of hardwood or standard bricks over decorative ones. Choose quality over luxury—durable finishes that stand the test of time without inflating costs.

Simplify Your Design

A straightforward layout (e.g. square or rectangular shapes) minimizes construction time and reduces costs for materials and labour. Avoid complex roof designs or bespoke structural elements unless necessary.

Plan Ahead to Avoid Changes

Mid-project changes are one of the biggest contributors to budget overruns. Finalize your plans early to keep costs predictable.

Get a Personalised Quote from Adapt Planning

While our extension cost calculator is an excellent starting point, nothing beats personalised advice from local experts. At Adapt Planning, we specialise in architectural design and planning consultancy for Bristol, Bath, North Somerset, and South Gloucestershire.

With the right tools and expert advice, your extension project can stay on budget and meet your vision. Start planning with Adapt Planning today—Bristol’s trusted partner in residential extensions.

Contact Us

Talk To Us about your project

Expertise Across Diverse Project Types

No matter the scope of your project, our expertise ensures it is handled with precision and professionalism.

House Extensions

Add valuable living space while enhancing your property’s appeal.

Loft Conversions

Transform unused roof space into a functional, beautiful area.

Annexes

Create self-contained living spaces perfect for multigenerational households.

Garage Conversions

Maximise underutilised spaces to increase functionality.

Garden Rooms

Add modern, stylish outdoor living spaces for work or leisure.

Driveways

Plan and design practical yet visually appealing home parking areas

New Builds

Manage every step of creating bespoke homes tailored to your needs.

Home Offices

We design and plan home offices. Transform your space to work from home

How accurate is the calculator? ▸
Our extension cost calculator provides estimates based on typical costs in Bristol and the surrounding areas. While accurate for budgeting purposes, exact quotes depend on factors like your contractor and specific site conditions.
Do I need planning permission? ▸
Not all extensions require planning permission. For example, smaller projects may fall under permitted development rights. Visit our page on Permitted Development to learn more.
What hidden costs should I watch for? ▸
Be mindful of potential expenses like groundworks (e.g., unexpected soil issues), utility relocations (e.g., moving gas or water lines), and additional building regulation fees. Read about our Planning Feasibility services to avoid surprises.
What is the typical timeline for a home extension? ▸
The timeline depends on the size and complexity of the project. Smaller single-storey extensions may take 3-4 months, while larger double-storey projects can take 6-9 months. Learn more about House Extension Services.
Can I extend my property in a conservation area? ▸
Extensions in conservation areas often require planning permission, and additional restrictions may apply. Our Planning Appeals experts can guide you through this process.