Liquid PU membrane blistering

A practical decision sequence

Diagnose the cause, then verify the repair.

Use the site evidence to agree a project-specific method with the responsible engineer, concrete producer, manufacturer or specialist applicator.

01 / Symptom

What is happening?

Bubbles develop under or within a liquid-applied membrane.

02 / Inspect and test

Evidence to collect

Check substrate moisture, dew point, primer cure, trapped air and coating thickness.

03 / Likely mechanism

Why it can fail

Moisture vapour, outgassing or incompatible recoat timing can cause blisters.

04 / Technical response

Choose the system

Remove defective areas, correct substrate conditions and reapply a compatible primer and membrane.

05 / Site execution

Control the application

Follow manufacturer moisture, temperature, film-thickness and recoat requirements.

06 / Acceptance

Verify the result

Check cured thickness and adhesion, then test details before protection.

Avoid this shortcut

Do not puncture and overcoat blisters without identifying their cause.

These guides are editorial starting points, not a project specification. Confirm the design, product data, substrate conditions and inspection plan for the actual site.

Technical references

References inform the topic; they do not endorse a specific product for this project.