Most manufacturers of floor coverings and adhesives recommend installing an impermeable covering on concrete floors only when moisture flow through the concrete is less than 3 lbs/1,000 sq ft/24 hrs. But problems with loose floor coverings and blistered coatings have increased in the last 10 years due to greater use of fast-track construction methods. Many owners want faster completion of their buildings, which shortens the drying time of concrete before coverings or coatings are applied.
In 1965, Portland Cement Association researcher Harold Brewer studied moisture movement through concrete to answer questions about water flow through residential basement slabs. His work can be used to answer the following basic questions about the drying of commercial and industrial concrete floor slabs:
- Is 3 lbs/1,000 sq ft/24 hrs an achievable moisture requirement? If so, how long does it take?
- Do capillary breaks or vapor barriers affect vapor-emission rate?
- What happens to the moisture content of the concrete when an impermeable covering is placed on the top surface?
- For concrete typically used in commercial and industrial floor slabs, what vapor-emission rates and degree of saturation are possible after the slabs have been exposed for one year to air at 73-degrees F and 50% relative humidity?