Paint film loses its adhesive quality and disunited from original surface, creating a swollen appearance on paint. Paint type which tends to encounter with this problem include high quality paint or one with high film density. Blisters typically arise from coating walls that is high humidity, such as damp plaster walls or surfaces exposed to direct sunlight. When moisture evaporates from inside to outside, blisters hence emerge. Other possible causes include moisture or leakage from the rooftop, cracked walls, leakage from the plumbing system, or moisture surging from the ground. Connecting walls, such as fence walls or roof walls, which are left unpainted can be the cause too, as well as using high quality paint on dusty surface, such as gypsum wall.
Differentiate the cause of leakage you are encountering, which can be arisen from leaving the top edges of the wall uncoated, having cracks on surface, using non water-resistant paints, having moisture trapped inside, improper wall slope to broken plumbing. Then repair all leaks detected. Possible solutions include filling cracks, coating the wall with water-proof paint, adjusting wall slope, fixing broken plumbing, for examples. Once the leaks solved, remove blisters and old paint, leave dry, prepare original surface with primer and refinish.
In case the blisters are caused by leakage from the backside of unpainted wall, remove blisters and old paint. Leave dry, prepare original surface with primer and refinish. Paint the backside of the wall to prevent leakage.
In case the blisters are caused by leakage surged from the soil up to the floor, which typically accounts for 15-30 cm., remove paint in all affected area. Leave dry, prepare original surface with primer and refinish. Paint the backside of the wall to prevent leakage.