Plaster Applied To Interior Of Interior Wall Problems

CMU

Plaster applied to this CMU is spalling and cracking the block and concrete. This wall is an exterior wall and gets rain and hot sun in afternoon. Plaster is applied to the interior surface and thhen painted with gloss latex. It is now blistering and resulting in spalling of interior surface. I think water vapor is coming from outside to insie during rainy cool times and travels to interior plaster. Then plaster is re-activated and any salts or other soluable chemicals are disolved and trapped between painted interior surface, plaster and surface of block wall and then when outside CMU wall is heated from sunlight, the moisture vapor travels towards the exterior bringing with it salts and other chemicals that travelinto the block wal, dry and turn to crystals causing an expansion effect inside the cement blocks and concrete and "spalling: interior wall! Anyboy have a different idea??

Jim

concretemasonry

A very plausable situation/explanation.

The necessary things for spalling is moisture and an non-breathing paint (low permeability or too thick).

You really do not know where the moisture is coming from. For above grade masonry wall, the most common source is roofing, flashing (lack of or improper) and a wall that can allow moisture pentration.

You did not provide your location, so nothing meaningful can be said regarding the climate or condensation.

__________________
Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.