Moisture Issues Inside Walls

Closely related to the problem and a contributing factor is the indiscriminate use of underlayments by the industry: http://bob-wewer-underlayment-craze.blogspot.com/

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My Youtube - Bob Wewer

https://www.youtube.com/channel/UCBSMxlV209Rvj3p4IA8khlQ

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Active leaks detected by Infrared Thermal Imaging

http://dlvr.it/3lYJcX

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Bob Wewer writes about one of his calls that may be of interest to folks with interior moisture problems

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Interior moisture often causes trouble while not being recognized as the source.

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Bob Wewer inspects moisture problem with plaster walls

Efflorescence

From Wikipedia, the free encyclopedia

In chemistry, efflorescence (which means "to flower out" in French) is the loss of water (or a solvent) of crystallization from a hydrated or solvated salt to the atmosphere on exposure to air.

This is a case of efflorescence on plaster walls. The “bubbles” started occurring a year or two after installation of cellulose insulation that was pumped into the walls though holes bored into the plaster. The call came in to inspect the roof for possible cause of moisture infiltration. The exterior bricks had been pointed in an effort to stop any moisture problems emanating from the outside.

At first glance I could see clearly that interior moisture vapor in the winter months was being pushed through the plaster and condensing on the cold bricks on the exterior walls. There were holes left in the plaster from the insulators where the underlying members and substrate could be inspected. The cellulose was moist to the touch. My client had not heard that moisture could come from the inside of a home and travel through the plaster walls to condense inside the wall cavity. No roofing issues were found and the exterior had no evidence of deficiency that would cause moisture infiltration. Clearly the problem was related to interior moisture moving into the wall cavity and condensing on the cold brick in the winter.

Moisture collected inside the walls and within the cellulose insulation tends to migrate toward the dryer state. Especially in the summer months, trapped moisture moves through the plaster toward the dryer conditioned space. The moisture brings with it the salts from the masonry plaster showing up as “bubbles” on the inside of the walls.

The real expectation of mold inside the walls will be realized to some degree once the walls are removed. Moisture problems often cause mold issues. It is a fact of life that if you have food (cellulose), warmth to some degree and moisture, you will have mold. The only one of the three, food, warmth and moisture, that is controllable is the moisture.

Recommendation: Remove plaster walls and lath, insulation and dispose. Install rigid insulation in the limited space of 1” framing. Foam seal all joints where insulation terminates at studs. Install additional layer of 1/2” foil faced rigid foam and tape joints providing vapor retarder on warm side of insulation (in the winter). Install drywall and trim. Purchase hygrometer and monitor interior moisture.