A rough-order feasibility tool for early-stage decision-making — before you engage a quantity surveyor. Core £/m² rates come from a real QS feasibility estimate (Contra Faba, 1B The Crescent, Filey, Dec 2025); kitchen/bathroom, extension-shell and fee figures are blended with published UK market data (sources in the notes panel). This version fixes issues found in a second self-audit, including one likely-backwards assumption — see "what changed" in the notes panel.
| Description | Type of work | Size (m²) | Kitchen fit-out | Bathroom fit-out |
|---|
Total floor area entered: 0m² — check this doesn't double-count area (e.g. if an extension absorbs part of the existing plan, reduce the existing-house line to match).
Kitchen/bathroom cost doesn't scale neatly with room size, so it's priced by fit-out size (Small/Medium/Large), not per m². Refurbishment and Loft-conversion rates already assume one typical kitchen + bathroom spread across the floor — only pick a size here if a line needs an additional one (most commonly: a kitchen in a new extension). Nothing is pre-selected; pick "None" unless you mean to add one.
Applied to finishes and (for extensions) shell. Still an unverified rule of thumb.
Indicative only, not sourced from BCIS's real (paywalled) location factors.
Applies only to the extension shell and kitchen/bath fit-out rates below, which are already national averages — 50% avoids fully double-counting the regional adjustment on top of an already-blended figure. Yours to adjust; there's no formula for the "right" weight.
Applied to build cost only. Fees and party wall costs are handled separately below.
Suggested 10–15% for pre-1919 solid-wall properties. Applied only to Refurbishment/Cosmetic lines (existing fabric).
Suggested 5–10% if applicable. Applied only to Extension/Loft lines — conservation status mainly restricts new external work, not internal refurbishment. Confirm status with your local council first.
Suggests how many party wall agreements you likely need, below.
Default reflects Northern England/Yorkshire rates (~£400–£900 standard, higher for complex cases) — London runs 50–150% above the UK average. Sits outside contingency by design.
Suggested % updates below based on project size.
Off by default — UK fee agreements are usually a % of contract sum, not an unspent risk reserve. Tick this if you'd rather budget conservatively.
Some empty-property or dwelling-count-change renovations qualify for 5% VAT — check with an accountant, don't assume.
This is a blended average across whatever line types you entered — it isn't a single market rate. See "By line item" below for the actual rate driving each scope.
| Shell & core | £0 |
| Finishes (incl. any kitchen/bathroom fit-out) | £0 |
| Preliminaries (site overheads) | £0 |
| Period / solid-wall premium existing-fabric lines | £0 |
| Conservation / heritage premium extension/loft lines | £0 |
| Build cost subtotal | £0 |
| Contingency | £0 |
| Professional fees | £0 |
| Party wall allowance | £0 |
| Total excl. VAT | £0 |
| VAT (20%) | £0 |
| Estimated total | £0 |
| Description | Type | Kitchen | Bath | Shell | Finishes | Prelims | Subtotal |
|---|