Editor
Oliver Wakefield-Smith, Founder of Digital Signet. Background in consumer cost research, public-data analysis, calculator design, and comparison-content methodology. Not a chartered architect, not a chartered surveyor, not a Building Control officer. The site cites the institutions that are.
Editorial standard
Statutory and regulatory figures on the site are sourced to a primary public source: ONS, HMRC, gov.uk, Planning Portal, RIBA, FMB, LABC, HSE, legislation.gov.uk, or the relevant Local Authority. The build-cost £/sqm bands are the site's own transparent model, derived from public editorial benchmarks (FMB House Builders' Cost Guide, Homebuilding & Renovating, Urbanist Architecture) and labelled as a model rather than lifted from any paywalled index. The BCIS Tender Price Index is used only as a cost-movement check, since its free release publishes index movement, not absolute £/sqm rates. The sources ledger records each figure with verified date and next-review date. Inferred rates for quote-only vendors are not used. AI-generated cost benchmarks are not used.
Review cycle
Statutory figures (VAT, planning fees, CIL self-build exemption procedure) are reviewed every 6 months and after any consultation outcome. The model £/sqm bands are reviewed quarterly against public editorial benchmarks and the BCIS All-in TPI movement. Regional rent figures are reviewed at each ONS Private Rent and House Prices UK bulletin. The calculator engine itself is reviewed annually for line-item completeness.
How the calculator is maintained
Calculator rates live in version-controlled source files: src/lib/calculate.ts for the engine; src/data/regions.ts for regional multipliers and median rents; src/data/sources.json for the provenance ledger. Each update commits a changelog entry to the public repository.
Errata + corrections
If you spot an error or a figure past its next-review date, please get in touch via digitalsignet.com. We update the on-site figure and increment the verified date once the correction is checked against the source.
No affiliation
The site is not affiliated with BCIS, RIBA, FMB, HMRC, any contractor, any architect, any mortgage broker, or any building-control body. Where a brand or company is named in cost commentary, it is for reference only. We accept no payment for placement.