hairline basement cracks

Old 09-13-02, 11:49 PM
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hairline basement cracks

my calgary, alberta home is 10 years old and we have started to build out our basement. we decided to pull down the insulation to check all walls b4 we began. behind the insulation was a vapor barrier from the basement floor up to about 2 feet from the ceiling. behind the vapour barrier was moisture on the walls. Where there wasnt a vapor barrier it was dry. Is this normal?
Where there was moisture we applied some type of sealant - crystal coating over the walls. It called for a few applications and to dry between applications. Was this a good idea ?
We also found some hairline cracks in the walls and 2 very long ones starting at the bottom edge of the basement window and leading down to the floor. Are hairline cracks normal or is that a sign that its time to move? We drilled the cracks a little bigger and then cemented them back up. Was this a good idea?
The basement is 800 sq ft. how many heating vents and cold air returns do you recommend?
What is the best type of carpeting to lay on a basement foor and is a underlay recommended or will that hold the moisture in and eventually mold?
Old 09-20-02, 03:35 AM
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Concrete is porous and moisture will migrate through it. The poly next to the wall is called a moisture barrier. Its purpose is to prevent moisture entering through the walls contacting the framing & insulation. The moisture barrier should start at the top of the wall down to the floor with enough excess to lay under the bottom plate of the stud wall. If you intend to lay carpet and the budget allows, put poly on the floor, caulk all joints at wall & seams, strap the floor with treated 1x3 & sheath with 5/8 plywood. You can then underpad & carpet away. Or seal the floor and use a foam backed carpet directly on the concrete. It was not damp at the top two feet beacause the moisture in this area evaporated or wicked into the insulation. Once insulation is in place you install the "VAPOUR" barrier. This poly prevents the warmer moisture laden interior air from entering the wall cavity. When insulating leave the batts off the floor about 6". In case your basement ever floods the insul will not get soaked.
Hair line cracks are common in concrete & not to be alarmed, But you would be wise to measure length & width of the crack using a piece of string to follow the crack. Using a pencil, draw across the crack at intervals. If the crack grows and pencil marks separate you have a live crack & should have a pro look at it. Good luck!

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