Methodology
Visible assumptions, replaceable evidence.
The internal path derives measured wall and ceiling area, supports repeated similar rooms and applies a job-specific 2026 rate band. The rendering path starts from net external wall area, separates four render systems and shows access or scaffold allowances. Both expose surface and regional adjustments rather than claiming postcode-level accuracy.
How the model works
- Walls, ceilings and external elevations use measured surface area rather than floor area alone.
- Skimming, replastering, plasterboard-and-skim, lime and four render systems use distinct evidence bands.
- Repeated-room, surface-condition, region and scaffold assumptions stay visible.
- Small-job minimums prevent implausibly low outputs from a bare per-m² multiplication.
- The result does not assume waste, VAT, decoration, structural repair or making good unless the written quote states them.
What the result means
The low and high values are planning bounds. The midpoint is simple arithmetic, not a prediction of the most likely contractor or carrier price. The calculator cannot inspect a property, verify a shipment, choose a legally suitable system, reserve capacity or issue a quotation.
Review date: 14 September 2026. We change a model only when the source, calculation and reason for the change can be recorded.
Current evidence snapshot
These are dated UK market observations used to bound a measured-area planning model. They are not additive line items, a promise of local availability or a substitute for inspecting the background and access.
- Skimming: £15–£30 per m²
MyBuilder's August 2026 UK observation; Checkatrade separately reports a £24 per-m² average.
- Medium-room re-skim: £430–£550
Checkatrade's June 2026 observation for an approximately 3m × 3m room.
- Medium room from scratch: £575–£920
Checkatrade's June 2026 observation; scope is materially wider than a finish skim.
- Ceiling skim: £200–£725
Checkatrade's June 2026 observations from a 9m² small ceiling through a 25m² large ceiling.
- Plasterer day rate: about £300
Checkatrade's June 2026 UK planning average; materials and scope still need to be stated.
- Traditional lime plaster: £50–£100 per m²
Current Homebuilding expert observation; suitability depends on the building fabric and coat system.
- House rendering: £30–£80 per m²
Checkatrade's June 2026 facing-wall observation across render types.
- Render systems: £40–£100 per m²
MyBuilder's August 2026 span from sand-and-cement to silicone; EWI is listed separately above this span.
- Rendering scaffold example: £500–£2,500
MyBuilder's current project allowance showing why access stays separate from the finish rate.
Source register
- Checkatrade room-skimming cost guide
June 2026 room, ceiling, day-rate and per-m² observations; reviewed 14 September 2026.
- MyBuilder plastering cost guide
August 2026 skim, full-plaster, room and specialist-finish observations; reviewed 14 September 2026.
- Checkatrade house-rendering cost guide
June 2026 external-rendering, system, property and scaffold context; reviewed 14 September 2026.
- MyBuilder rendering cost guide
August 2026 render-system, preparation and access observations; reviewed 14 September 2026.
- HSE asbestos material guidance
Official textured-coating and disturbance boundaries; reviewed 14 September 2026.
- SPAB lime guidance
Traditional-building material compatibility and breathability context; reviewed 14 September 2026.
- TrustMark homeowner checklist
Written-quote, contract, references and payment-stage guidance; reviewed 14 September 2026.
Error corrections
If a source is outdated or a calculation does not behave as described, email [email protected] and identify the URL, input and expected result. Do not include private customer or property information.