Blisters and lifting on a flat roof

A raised patch on a flat roof can prompt an immediate urge to flatten it or cover it with sealant. The visible change is better treated as information for an assessment. Its shape alone does not establish the cause, the condition beneath it or the repair required.

Flat roofs use different materials and assemblies. A description that is useful for one covering should not be treated as a diagnosis for another.

Record the location and timing

Note when the change was first noticed and whether there is any related water entry indoors. Include nearby rooflights, outlets or wall junctions in a photograph taken from a safe viewpoint. If older images exist, keep them for comparison.

Do not puncture, press or cut a raised area to investigate it. Disturbing the covering can change the condition that needs to be assessed and introduce a new opening.

Separate appearance from performance

Tell WWR Roofing whether the concern is a visible change alone or a change accompanied by leakage. Previous overlays, patches or repairs are relevant background if their details are known.

The assessment should distinguish the observed surface from what remains uncertain underneath. Where closer investigation is proposed, establish its scope and how the roof will be left afterwards.

Give the repair a defined boundary

A local repair, an overlay and a replacement covering are different proposals. The recommendation should explain the chosen extent and the suitability of any material retained. Avoid assuming that applying another layer settles the underlying cause.

Keep the finding, agreed work and follow-up recommendations in the roof record. Our flat roofing page is the route for an enquiry, while repair or replacement explains the wider decision once the condition is understood.