I hope this doesn’t get too long but I’d like to make sure I get the details down.
I have a storage room that is part of a basement. It’s 7′ or so below grade. I built the bottom shelf by nailing 2×4’s to the concrete floor parallel to the front of the shelves and then throwing some MDF sheets on top of them. The 2×4’s run side wall to side wall so I effectively created 2 channels with zero air movement. Mold has started growing on the bottom shelf only. I took all the shelves apart so I could analyze. I found the concrete under the shelves had condensation. Very little mold was growing under the shelves. There is no condensation on the rest of the concrete slab, so it’s obviously a function of low air movement. There is no water penetration through the foundation, that much I know (good exterior drainage system). I built the storage room a little over 30 days after the slab had been poured and it was completed in late March.
Looking for thoughts on root cause and solution. My best guess is that I just need some airflow under that shelf. I also don’t think that the problem is water from the green concrete, though I might be wrong about this (in which case the problem might go away?). I should also note that a large part of my basement floor has not been poured yet (600 sq ft) – it’s just gravel over dirt. This entire space is part of the conditioned air, so my central AC is contributing to removing some of the moisture from this area.
My solution is to tear up the 2×4’s from the floor and run 2×4’s front-to back 24″ oc providing 1.5″ clearance to the floor. I was going to hold the bottom shelf off the wall by 1″ allowing airflow from the back of the shelf too. I was also going to put some kind of fan in the room to stir up the air, mainly directing it at the floor.
Thanks -MERC
Replies
The most immediate problem is that there isn't air flow under the shelf, but you are also mistaken that no moisture is coming from the crete. Green crete will let go of considerable moisture for 9-12 months after pouring. Also, if there is no VB under the slab and no sealler applied to the slab surface, the is a definite probability that moisture is migrating from the ground to the air space thru the slab.
So seal it good and then rebuild the shelf with air flow potential.
BTW, Mold seems to love MDF. It's the Hilton of man made woods for mold to stay for the convention.
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Thanks for the reply Piff. You are always a first responder.
There is a vapor barrier under the slab and we sealed the slab, though the sealer acter weird. It only "took" in certain spots and has since retreated even more. So basically the floor looks like crap, but I don't really care about that.
So I'll rebuild to get airflow and hope that 1.5" clearance is enough to discourage mold growth.
MERC
If you are still using MDF, try painting it to resist providing a home/meal for the stuff and maybe sprinkle some borax under it.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
>>[MDF]is the Hilton of man made woods for mold to stay for the convention.
Well put!
On the paint idea, I believe many exterior paints are now including mold inhibitors, as well as paints specified for bathrooms.