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Insulation - Cavity wall – cost per m² – UK 2026 Rate Guide

Budget rate for supply & lay · typical budget rate before your adjustments

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Insulation - Cavity wall
per m² · supply & lay
£22 – £77 / m²
What is it

Cavity wall insulation is thermal insulation installed between the inner and outer leaves of a masonry wall, including standard cutting, fitting and retaining clips.

Rate guide
Standard 100mm full-fill mineral wool slab£22 – £32/m²
150mm full-fill mineral wool slab£29 – £42/m²
90–100mm partial-fill PIR board£46 – £66/m²
110–120mm partial-fill PIR board£55 – £77/m²
Blown mineral fibre to existing cavity£28 – £43/m²
Labour output
Clear repetitive elevations with coordinated wall ties90–130 m²/gang-day
Typical housing elevations with regular openings60–90 m²/gang-day
Multiple openings, corners and frequent board cutting35–60 m²/gang-day
Broken-up work, restricted access or remedial installation20–35 m²/gang-day
Key rate adjusters
Insulation thickness
Increasing mineral wool thickness from 100mm to 150mm typically adds £6–£10/m².
Board specification
Moving from mineral wool to partial-fill PIR generally increases the installed rate by £18–£30/m².
Elevation complexity
Frequent windows, returns and stepped masonry can add 15–30% through cutting and reduced output.
Order size
Small plots, fragmented releases or minimum-load deliveries can increase rates by 10–20%.
Access and sequencing
Scaffold congestion or work out of sequence typically adds £3–£8/m² to installation cost.
Enhanced fixing
Extra retaining clips, taped joints or demanding exposure-zone details can add £2–£7/m².
Quantity surveyor insights
  • Waste and buildability: Allow 5–10% material waste, rising for board systems on heavily fenestrated elevations; coordinated wall-tie spacing and board modules materially improve output and reduce offcuts.
  • Scope and procurement: Confirm whether the package includes retaining clips, joint tapes, cavity closers, fire barriers and insulation to reveals, as these are common scope gaps. Secure the specified thermal product early because substitutions may require revised condensation analysis and designer approval.

Estimate Anything AI answer · indicative budget rates · updated 31 August 2026

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