What would cause an acrylic adhesive used to glue hardwood flooring to a concrete slab to remain "sticky" a year after installation?? I can ply the planks of engineered hardwood off my floor with a butter knife and underneath is a sticky mess. Please someone explain to me what happened.
Thank you in advance!!!!

In the "old days" when we used chlorinated solvent adhesives, if they were not allowed to "tack out" for at least an hour, they would stay sticky and not set. But todays urethane adhesives, whether they are acrylics or solvent based, typically dry well. Find out which adhesive was used and contact the manufacturer.

Could be a high ph content of the concrete and or high vapor emissions.