Compare the method, roof risk and evidence—not just the price

Open-cell and closed-cell are context, not a method

Record the foam type only where documentation or a competent inspection supports it. Open-cell and closed-cell products can have different properties, but the label alone does not establish adhesion, roof condition, suitability of a technique or what evidence will satisfy a separate decision maker.

Sources for this section: RICS consumer guide to spray foam insulationUK government moisture-risk study

Access determines what can be seen and reached

Ask how the roof space, eaves, junctions, narrow bays and concealed faces will be accessed safely, what enabling work is included, and which areas will remain uninspected or untreated. RICS notes that foam can restrict the view of the timber roof structure; the proposal should not turn restricted access into a confident condition statement.

Sources for this section: RICS consumer guide to spray foam insulation

Substrate, felt and timber need an explicit risk plan

Identify what the foam is bonded to, such as timber, an underlay or felt, or the roof covering, and ask how the proposed work will avoid or manage damage to each element. RICS describes removal as potentially damaging to an existing structure and notes that products and roof underlays differ, so a generic technique is not evidence of suitability.

Sources for this section: RICS consumer guide to spray foam insulation

Ventilation and moisture questions survive the removal decision

Ask how the existing roof build-up manages moisture, what ventilation and vapour-control layers are present, what readings or observations are meaningful, and whether conditions need recording before and after work. The government study models specific combinations of open- or closed-cell foam, underlay resistance, vapour control and climate; its scenarios are context, not a remote diagnosis.

Sources for this section: UK government moisture-risk studyRICS consumer guide to spray foam insulation

The written method should name duties and limits

Ask who controls the work, how health and safety risks are managed, what protection and making-good are included, and how changes will be agreed. HSE states that domestic-client duties normally pass to the contractor on a single-contractor project or to the principal contractor where more than one contractor is involved, subject to the appointment arrangements it describes.

Sources for this section: HSE domestic client duties under CDM 2015

Agree the waste route before work starts

The written scope should identify who removes material from the property, the intended waste route, which waste records will be supplied, and what happens if the material or roof condition differs from the assumptions. Treat a missing answer as a comparison gap rather than inventing one.

Sources for this section: RICS consumer guide to spray foam insulation

Define completion evidence before accepting the scope

Agree the areas and stages to photograph, how remaining foam and any damaged or replaced roof elements will be recorded, and which scope, variation, invoice and waste documents form the completion evidence. RICS recommends records and photographs before, during and after building work, including roof condition, ventilation and moisture information.

Sources for this section: RICS consumer guide to spray foam insulation

Make the follow-up inspection answer a named question

Decide who will carry out any follow-up inspection, when the property-specific adviser says it is meaningful, what can be inspected then, and what limitations will remain. Return the resulting evidence to the named lender, valuer, buyer or roof professional if they requested it; do not assume work or a certificate determines their outcome.

Sources for this section: RICS consumer guide to spray foam insulation

Next steps

1. Give each assessor or contractor the same installation record, roof evidence and purpose for the work.
2. Compare written access, method, protection, exclusions, waste, completion and follow-up terms side by side.
3. Resolve material differences with the appropriate independent professional before authorising irreversible work.