How We Calculate Costs

Transparent methodology so you can trust our estimates and understand how they were built.

Our Data Sources

We build our cost estimates using the following sources:

  • Tradesperson day rates — surveyed from Checkatrade, MyBuilder, Rated People and direct tradesperson quotes published online
  • Material costs — from B&Q, Wickes, Tile Giant, Wickes, Jewish Enhanced, and builder merchants including Travis Perkins and Jewsons
  • Industry benchmarks — BCIS (Building Cost Information Service) published rates, JTC (Joint Contracts Tribunal) rates
  • Regional adjustment data — BCIS regional location factors and Office for National Statistics (ONS) construction price data
  • Planning and building regulation fees — directly from UK Government and local authority fee schedules

Cost Ranges, Not Single Figures

Every calculator shows a range — a low figure and a high figure. This is deliberate. No two renovation projects are the same, and presenting a single figure implies a false precision that doesn't serve you well.

Our ranges represent:

  • Low estimate — budget specification, competent but value-focused tradespeople, standard materials
  • High estimate — mid-to-premium specification, recommended quality tradespeople, better-grade materials
  • Exceptional circumstances — (e.g. structural complications, specialist materials) may push costs beyond our high estimate; these are flagged in individual guides

Specification Levels

Each calculator asks you to select a specification level. These are defined as:

  • Budget — suitable for rental properties, tight budgets, or properties where the owner doesn't plan to stay long. Basic quality finishes. appliances and sanitaryware.
  • Mid-Range — the most common choice for family homes. Good quality finishes, named brands (e.g. Howdens, Wickes), mid-spec appliances. This is what most homeowners spend.
  • Premium — high-specification finishes throughout. Designer kitchens, premium appliances (Miele, Neff), quality sanitaryware. For high-value properties or homeowners who plan to stay long-term.

Regional Adjustment

UK construction costs vary significantly by region. Our regional multipliers are derived from BCIS Location Factors. London is the most expensive region, typically 35–45% above the UK national average. Scotland and the North East are typically 5–15% below average.

Labour vs Materials Split

Our calculators separate labour and material costs because:

  • Materials are relatively fixed in price; labour is the larger variable
  • Tradesperson rates vary more by region than material costs
  • Knowing the labour cost separately helps if you're considering doing some of the work yourself

Contingency

Every calculator includes a mandatory 10% contingency on top of the base estimate. Industry standard is 10–15% for renovation projects. This is not padding — it's a recognition that most renovation projects encounter unexpected issues once walls are opened up, floors are lifted, or old fixtures are removed.

What Our Estimates Don't Include

  • VAT (we quote excluding VAT; always confirm with your contractor whether prices are inc. or ex. VAT)
  • Architect fees (typically 5–10% of build cost for extensions and loft conversions)
  • Planning application fees
  • Structural engineering fees
  • Party wall agreement costs
  • Alternative accommodation costs during renovation
  • Furniture, soft furnishings, or decorative items

How Often We Update

We review and update all cost data at least quarterly. Material costs and tradesperson rates can change with inflation and market conditions. If there is a significant market movement (e.g. a major change in timber or fuel costs), we update as soon as reasonably possible.

Known Limitations

  • Estimates are for standard UK residential properties. Commercial properties, listed buildings, and non-standard construction (e.g. steel frame, thatched roof) may cost significantly more.
  • Our calculators do not account for properties with significant structural problems (subsidence, Japanese knotweed, major damp) — these require specialist surveys.
  • Costs can vary significantly in rural locations with limited contractor availability.
  • Scotland and Northern Ireland have some different building regulation requirements; our England/Wales figures are generally close but not exact for these nations.

Feedback and Corrections

If you have a quote from a tradesperson that suggests our data is significantly out of date, please let us know. We review all correction submissions and update our data quarterly.