My condo is on the 3rd floor & I'm looking to replace the 3/4 white oak floor with 5/8 strand woven bamboo.After removing some of the oak I have found that the sub-floor is a concrete slab (I'm unsure of the thickness) covered by 1/8 of insulayment underlayment. On top of that are two(2) layers of 3/8 plywood screwed to eachother with 3/4 screws. The plywood is not attached to the 1/8 insulayment mat or the concrete slab in any way. So my first question is, is this normal floor construction?My seconod question has to do with the fact that there appears to be green mold between the plywood planks & behind the baseboard. Should I be worried?Thanks in advance. I appreciate any help you can offer.
It is pretty common to use a plywood underlay in concrete muti-story residential. It acts to keep the floor covering warm and dry. a vapor barrier layer is also a must have. The green mold may not be mold at all, it can be a form on oxidation due to moisture inherent in concrete. If you tear out the plywood, you should replace it for your flooring to last. a strong bleach mix and mop will kill mold.
You should be worried about the mold. Although it doesn't sound like a wide spread and only in specific areas. In New York City high rises the wooden floor sits right on top of the concrete slab (with glue) and acts as a pretty good insulation. The extra insulation might be helpful especially in northern states where temperatures fall sharp below freezing. You can safely remove everything and place your new floor right over the concrete. BUT make sure to clean the mold well enough. Mold cleaning and odor removing can be done in two stages. 1. Regular household vinegar can remove odors. And 2. chlorine will kill the molded areas.
As the others have said it is normal construction. We 'float' the floor like that all the time. It's better if you live in a place where the weather changes dramatically. It allows the floor to expand and contract. As for the green stuff...it's probably mold, it's better to treat it, then to take a chance. I don't think it would be efflorescence (stuff that naturally comes out of the concrete), it's usually white. Remove a piece of drywall and see if it's traveled up the studs. Either way- clean it up before laying any flooring.
