When should sealer be used on concrete slab

Old 10-12-05, 10:59 PM
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When should sealer be used on concrete slab

Iím planning on gluing engineered flooring to a concrete slab that was poured about a year ago. There are a couple of cracks in the slab, but nothing too major. Can I prep the slab by filling the cracks with silicon caulking to block future moisture from coming through the cracks, and improving the flatness with a leveling cement? Then determine the moisture level with a meter that I hope I can rent somewhere. Then, if itís dry, begin gluing the flooring directly to the clean, dry concrete slab? I understand that the glue will act as a moisture barrier to protect the wood during future rainy seasons. On the other hand, if itís not dry enough now, should I then apply a sealer before installation? Do I have this right? Or do I need a sealer to protect against future moisture regardless of the current moisture reading? And if so, why do I even need to measure the moisture level?

Old 10-13-05, 08:16 AM
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Testing of the vapor emissions is to see if it exceeds the required amount for a lasting installation.

Urethane adhesives act as a moisture retarder, not a moisture blocker. I have done failure analyst on many cupped or delaminated wood floors that were told the urethane glue is a moisture barrier.

If your slab shows levels way below 3# per 1000 sq.ft. then the added cost of the moisture blocker is not needed. If your slab is real close to the 3# or exceeds it, you better use a blocker and adhesive system.

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