True or False: When concrete will be placed directly on a vapor retarder, finishers should punch holes in the vapor retarder to speed finishing.

True or False: When concrete will be placed directly on a vapor retarder, finishers should punch holes in the vapor retarder to speed finishing.

• A. True
• B. False
• C. Not Applicable
• D. Not Sure

Answer: (B)

Punching holes in a vapor retarder under a slab defeats the purpose of that barrier. The vapor retarder is there to slow moisture moving from the ground into the concrete and toward the surface as it cures. Creating openings gives moisture an easier path to escape or migrate, which can lead to uneven drying, surface drying too fast, and moisture-related finish problems such as cracking, curling, efflorescence, or staining. It also undermines the barrier that helps control vapor transmission for toppings or coatings. Finishing should be done with the barrier intact and with proper curing methods to maintain moisture balance, not by compromising the barrier’s integrity.

Punching holes in a vapor retarder under a slab defeats the purpose of that barrier. The vapor retarder is there to slow moisture moving from the ground into the concrete and toward the surface as it cures. Creating openings gives moisture an easier path to escape or migrate, which can lead to uneven drying, surface drying too fast, and moisture-related finish problems such as cracking, curling, efflorescence, or staining. It also undermines the barrier that helps control vapor transmission for toppings or coatings. Finishing should be done with the barrier intact and with proper curing methods to maintain moisture balance, not by compromising the barrier’s integrity.