Flat roofs

Can Resitrix SKW be installed over insulation?

Short answer: It can form part of a compatible warm-roof system, but the insulation, facing, adhesive or carrier layer, vapour control and perimeter fixings must be designed together.

What this means in practice

Flat-roof performance depends on the whole build-up: structural deck, vapour control, insulation, falls, waterproofing, outlets, kerbs and edge details. Choosing a branded membrane while ignoring trapped moisture or poor drainage simply locks the original fault beneath a new surface.

What to check next

  • Use a manufacturer-compatible build-up
  • Check wind-uplift restraint
  • Maintain insulation continuity at kerbs and edges

When should you ask a roofer to inspect it?

Arrange a survey for recurring leaks, soft or deflected decking, persistent ponding, split details, blistering or an unknown build-up. Openings may be needed before anyone can responsibly confirm whether an overlay is suitable or the roof must be stripped.

Safety first: do not climb onto a roof without suitable access, training and protection. Keep clear of loose coverings, unstable ceilings and water near electrical fittings.

Technical content reviewJ & L Welch Roofing & Paving Services Ltd · Over 20 years of combined roofing experienceReviewed 28 August 2026 · How our answers are produced

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