How Quoteio prices your project
In shortWe build each price from trade-level rates taken from 41 completed Living Design & Build jobs in the West Midlands, adjust it with a cost index for your postcode, add professional and statutory fees and VAT, then show a range that is tighter where we hold our own job data.
1. Base rates from completed jobs
Our starting point is the costing sheet and final accounts of completed extensions, loft conversions, garage conversions and renovations by Living Design & Build, a West Midlands building company. Rather than a single price per square metre, we price the parts of a build: footings per linear metre, the slab and screed per square metre, external walls by area after openings, the roof by type, fascias and guttering, plastering, joinery, scaffold and drainage.
Electrics and plumbing are priced from a regression across those jobs (a fixed start-up cost plus a cost per square metre), because they don’t scale neatly with size. Labour is added at the ratio we see between labour and materials on real final accounts. Lofts are priced as a shell plus a cost per room, since steels, stairs and the dormer box don’t double when you add a second bedroom.
2. The postcode cost index
Every one of the UK’s 121 postcode areas has a factor against our West Midlands base of 1.00. Region factors are calibrated from published regional tender price indices, then widened for domestic work, where the London and South East premium is larger than on commercial jobs. On top of that we adjust for known local pockets: commuter towns, Highland and island sites, and cheaper conurbations. In the West Midlands we go down to each postcode district.
Kitchens, sanitaryware and glazing are mostly supply cost, so only 60% of the local adjustment applies to them. Planning fees are set nationally, so they follow each nation’s official schedule and are never scaled.
| Region | Index |
|---|---|
| Inner London | 1.38 |
| Outer London | 1.24 |
| South East | 1.13 |
| East of England | 1.08 |
| South West | 1.05 |
| West Midlands | 1.00 |
| Scotland | 1.00 |
| East Midlands | 0.99 |
| North West | 0.99 |
| Yorkshire and the Humber | 0.96 |
| Wales | 0.96 |
| North East | 0.94 |
| Northern Ireland | 0.90 |
3. Fees and VAT
Extensions include architectural drawings, a structural engineer, building regulations and the householder planning fee. Loft conversions include a lawful development certificate (most are permitted development) and a party wall surveyor. Garage conversions include drawings and building regulations. Renovations include building control sign-off only.
- England householder planning fee: £528, lawful development certificate £264, new dwelling £588.
- Wales householder fee: £585.
- Scotland householder fee: £312.
- Northern Ireland householder fee: £327.
VAT at 20% is included on extensions, conversions and renovations. New dwellings are zero-rated for VAT, so new build estimates show none.
4. How the range is set
No honest estimate is a single number. We show the calculated price as a range, and the width depends on how much evidence sits behind it:
- Our own job data (DY, WV, WS, B, TF, WR, SY postcodes): 6% below to 8% above.
- Index-priced areas across the rest of the UK: 8% below to 10% above.
- London: 10% below to 12% above, because site access and party walls vary so much.
- No postcode: 10% below to 12% above.
Lofts add one point either side, renovations and new builds two, and landscaping four, because our landscaping rates are still being checked against invoices. The range is a little wider above than below because overruns are more common than savings on real jobs. As an example, a 20m² single storey rear extension at West Midlands rates comes out at £54,000 to £62,000.
5. What an estimate leaves out
Ground conditions you can’t see (poor soil, tree roots, a sewer under the footprint), knocking through to the existing house, moving a boiler, kitchen appliances, decorating and landscaping after the build are not included unless you add them. A builder will confirm these after a site visit.
6. Reviews and updates
We review the index every quarter against new jobs and published indices. This page shows the current edition (2026-Q4). Our server re-prices every estimate when it is saved, so emails and PDFs always match the current figures.