Saturday, January 11, 2014

Moisture Vapor Emission in Concrete

HoustonFloorCoatings.com received a phone call from a home owner who said that the concrete slab in her home would get wet and leave behind salt deposits on the surface every time it rained outside.  After arriving to the home we discovered that the slab did indeed show signs of a rare occurrence called MVE, or Moisture Vapor Emission.  MVE is an occurrence which is caused by water attaching itself to salt molecules and being forced up and thru a concrete slab where it reaches the top and evaporates into the air leaving the salt deposits behind on the floors surface. Most homes have a moisture vapor barrier (a tarp) installed below the concrete slab which will prevent this occurrence, but this home owners vapor barrier was destroyed when plumbers dug below the slab and reinstalled the homes plumbing.  Since the pressure of MVE can be so great, it can cause tile or epoxy at the surface to buckle and peel. There are products that claim to block MVE to a certain amount of pressure, but the problem is that if the pressure is too great, these specialty coatings will also fail. The only way to be sure that a coating will perform under these conditions is to install a breathable water based coating such as Sherwin Williams Aqua Armor Epoxy, which will allow the moisture to pass thru the coating while filtering out the salt deposits.  Houston Floor Coatings prepared the home owners slab by diamond grinding and applied several coats of Aqua Armor Epoxy at a total of 20 dry mils in thickness.  After the coating was applied, the salt deposits did not return and the coating slowed down the moisture enough so that it evaporated immediately upon reaching the surface instead of puddling.




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