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Problems, removal and repairs

Damp investigation after cavity insulation

A damp investigation finds out why an insulated wall is showing damp or mould: rain getting in through defects, bridged or wet fill, debris in the cavity, a breached damp-proof course, or condensation. The cause decides the cure.

Moisture meter held against a damp, mould-spotted corner of an external wall indoors

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Common causes we check

Defective pointing, cracked render and porous bricks letting rain in; leaking gutters and downpipes; fill bridging the cavity where mortar droppings or debris have collected; ground levels above the damp-proof course; and condensation from cooking, drying clothes and too little ventilation.

What you get

Moisture readings, borescope photos at the affected areas, an explanation of the likely cause and the options, from simple repairs to partial or full extraction, each priced.

What is included

  • Moisture mapping inside
  • External defects check
  • Borescope at affected areas
  • Cause and options in writing

Damp investigation after cavity insulation prices

Damp investigation after cavity insulation guide prices
Damp investigation after cavity insulation guide pricesGuide price
Damp investigation with borescope£295–£495

This work is not insulation, so it is normally standard-rated for VAT. Guide prices include VAT where it applies. Guide ranges only: the fixed price is confirmed in writing before any work starts, and anything that could not be seen at survey is agreed with you first.

Rules and funding by nation

The building regulations route and the funding schemes differ between England, Wales, Scotland and Northern Ireland. The local pages for your area explain the rules where you are; in short:

  • England: Filling a cavity is notifiable building work and needs a building notice or competent-person self-certification.
  • Wales: Filling a cavity is notifiable work under the Building Regulations as they apply in Wales, usually self-certified through a competent person scheme.
  • Scotland: No building warrant is needed for insulation within a wall, but the work must meet the building standards.
  • Northern Ireland: Inserting cavity wall insulation needs a building control application to the council before work starts.

Sources: Energy Saving Trust: cavity wall insulation; Planning Portal: cavity wall insulation and building regulations; Welsh Government: building work competent person schemes; Welsh Government: issues arising from cavity wall insulation installations; CIGA: the CIGA guarantee; HMRC: VAT on energy-saving materials (Notice 708/6).

Last reviewed 19 October 2026.

Book a damp investigation in your area

Priced before you book. Findings in writing. No cold calls.