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Know your numbers before you start.
The Cost Planner, the verified builder directory, and plain-English guides: everything to plan a project before you speak to anyone.
Cost Planner
UK-wide indicative costs. No commitment. Pick a project type, size and region for a realistic range.
Project
Approximate floor area
30 m²Region
We match to the postcode area rather than the exact boundary. Your estimate is worked out in your browser. We keep a record of it, with no name or contact details, to improve the planner. If you have accepted analytics cookies, we link it to an enquiry you go on to send us.
Specification
Mid-range brands and finishes: what most projects use.
Specification sets the rate we price at. The range around it allows for what we cannot know yet, like site conditions and access.
Indicative budget range
Typically around £102,148
Extension · 30 m² · UK average · Standard materials
- Builder's work
- £70,500
- Design, structural and building control
- £6,300
- Planning application
- £548
- VAT at 20%
- £15,500
- Contingency (10%)
- £9,300
- Typical total
- £102,148
If the property has stood empty for two years or more, or the work changes the number of dwellings, VAT may be 5% rather than 20%. We can't verify that, so we've assumed 20%.
A split of the builder's work line only.
Indicative only. Site conditions, access, materials and planning move the final figure. Builders price the project, not the range. This isn't a quote. Rates v5, reviewed August 2026. How we calculate this →
Get real quotes for this projectRates, not guesses
Each trade carries essential, standard and premium rates, re-based against named public sources. We don't hold a BCIS licence and don't claim one.
Region and spec do different jobs
Spec picks which rate you're priced at. Region multiplies it: London (inner) ×1.30, UK average ×1.00, North East ×0.94. The range around the answer is a separate allowance for uncertainty.
VAT, fees and contingency are shown
Published UK build-cost rates exclude VAT. We add VAT, professional fees, the statutory planning fee and a contingency, each on its own line, so you can see what makes up the total.
Read the full methodology
Every rate, multiplier and source we use is published, along with when it was last reviewed.
How we calculate thisFound your range?
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