Mold/Wet/Damp concrete slab under carpet tiles with rubber backing
I have a commercial space in South Florida. The flooring we have chosen is a commercial carpet tile with 1/4" rubber backing. About four months ago we noticed a musty odor in the building each morning when we arrived. After checking the HVAC system and plumbing, we pulled a few of the carpet tiles and noticed the adhesive had re-hydrated and in some locations there was standing water. If the carpet tile was left off the floor, and the area was exposed for just a short time, the moisture would completely dissipate.
I drilled the concrete in three locations using a 2" masonry bit. I drilled down about 2 1/2" and found no signs of moisture. I employed one of the methods of testing I had seen used in another building which included the use of a piece of 8M film about one foot square taped down to the concrete with duct tape around all the edges. The following morning, the top of the film was dry but the bottom was saturated.
We reported the problem to the property owner who installed a "French Drain" around all sides of the building that had landscape planters. Next we pulled all the carpet, cleaned the old adhesive off the floor by spraying with warm water and scraping, and air dried the concrete with floor fans for eight hours. That was followed by new carpet tiles which also have rubber backing. Within one week, the moisture was back.
What could be causing this condition?
Hi Rick, did you get rain the week the carpet was off the concrete floor? It may be possible that some moisture infiltrated the concrete slab from Surface water. Another thought is that the moisture is coming from ground water inside the center area of the building under the concrete. Water seeks it own level and it also follows the path of least resistance. Another thing to check is are there any water feed pipes in the floor? Maybe if there is one it may have sprung a leak!
I don't know what else to tell you with out having the advantage of seeing it with my own eyes.
I'm located 25 miles west of Boston and would love to come to Florida and get out of the snow and cold of winter. Let me know if you have any further questions.
Good luck. Daniel