Why are there bubble-like bumps on my walls?

What is it?

These bubble-like appearances are caused by blistering, which happens when certain areas lose adhesion, forcing the paint film to lift from the surface. 

What are the possible causes?

  • Painting under direct sunlight or on surfaces that are too warm. This is especially true if the coating you’re using is dark in colour and solvent-based.
  • Applying an oil-based finish on a wet or moist surface.
  • High humidity or conditions where moisture seeps out of exterior walls. This is less likely to occur if you’re using a water-based paint as it allows water vapour to evaporate without reacting on the paint film.
  • Exposing water-based finishes to dew, high humidity or rain immediately after the paint has dried. This becomes a greater issue if the surface has not been properly prepared at first, or if the quality of paint is poor.

How can I fix this problem?

  • Start by checking if the blisters go all the way down to the substrate. If they do, it may be due to moisture from within.
  • Remove sources of moisture. Repair loose caulk and install vents and exhaust fans wherever possible.
  • Scrape and sand blisters till they go away. Prime any exposed wood and repaint.
  • If the blisters are on the surface only, the problem is likely to be caused by painting on a warm surface or under direct sunlight. It could also be because the painted surface was exposed to moisture soon after painting.
  • Do scrape and sand away the blisters in this case also.
  • Prime exposed wood and paint the wall with a high quality water-based exterior paint.