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It is a common misconception that any moisture related problem in a building must be caused by an active leak. There are many moisture related problems that come from water vapor that naturally comes from underground and penetrates the slab or sub floor in a crawl space.
Moisture problems occurring on a concrete slab, under wood or laminate flooring can be difficult to correct. The problem normally occurs when water vapor cannot move through the flooring and condenses between the slab and the floor covering or sub floor.
In most cases it is easier to change the flooring to carpet or tile than it is to try and stop the water vapor. Floor coverings that breathe typically don’t develop water vapor related damage. Most floor manufacturers require a low moisture content (8% or less) on a concrete slab before the flooring is installed. Keep in mind that a slab can test low for moisture, but develop problems after the flooring is installed.
Concrete slabs can be tested before installation by simply taping down a large square of plastic sheeting and letting it set for 48 hours. If the moisture levels under the plastic rise above 8 %( or manufacturer's specs.), it is probably a good indication the same thing will happen under wood or laminate flooring. In these cases it would be wise to go with a floor covering that breathes. There are a number of good concrete sealers that can be applied directly to the slab to try and limit the amount of water vapor that comes through the slab. However, there is always a risk of the problem reoccurring even on a sealed slab.
Water vapor causing damage in crawl spaces and in the sub-floor is more easily corrected or improved. The most common solution for curing a damp crawl space has been to try and improve the ventilation and air flow in these areas. This does help, but has some inherent disadvantages. There is still constant water vapor moving into the crawlspace and humid air coming in through the vents from outside.
The ideal solution is to lower the humidity and slow the amount of water vapor coming into the crawlspace.
With the advances in closed cell foam insulation it is now possible to completely |
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