Here's the background: Our house was built in 1928 and believe it or not, the concrete floor is in great shape. There are no cracks whatsoever, and it is 99.9% of the time dry. The basement is split in half, one half is the workroom and the other half is a finished part that used to have wall to wall carpet with an underpad.
Well, living in NH, we experienced a couple week's worth of constant rain in May that caused a ton of flooding statewide in parts of the state that are not prone to flooding. In our case, I'm sure the problem was that the water table rose too quickly and submerged the basement. The water seemed to seep up from the floor, not come in through walls or anything. It only ever accumulated to about 1/4" though, nothing too crazy.
Anyway, our carpet was ruined and now we need to figure out how we want to resurface the finished part of the basement. The trouble with the concrete is that it is painted in spots and very very rough (although no cracks). Also, it has a few (very few) spots that bulge upwards (less than 1/2" though).
We've decided that we want to lay FLOR carpet tiles (http://www.interfaceflor.com ) in the basement. They can be laid on wood, sealed concrete, tiles, etc.... Now the concrete itself is too rough to accept these tiles so we're going to need something put on top of the concrete.
I was first thinking of laying Ditra down using thinset, but now I'm shying away from the idea... .first, it is a horribly tedious job trying to clean up the paint which I'm assuming needs to be removed for the thinset to adhere properly. Also, I'm not sure if you'd be able to "feel" the Ditra underneath the carpet tiles since Ditra has those square "bubbles"...
Our latest eureka idea was to just lay down pressure treated plywood directly to the concrete and attach the carpet tile to the plywood. I know it would be better to have 2x4 spacers fastened to the concrete and the plywood attached to the spacers, but this is not an option as our current headspace is hovering around 6.25'.
Do you guys think it would be ok just laying down the plywood directly to the concrete, shimming where necessary? Or should I use 1x3 furring strips instead of the 2x4s just so I have SOMETHING (I have a feeling they won't be solid enough, though), or should I definitely go with the Ditra and not worry about the thinset on painted concrete since the paint is old and doesn't seem to be sealing anything anyway?
I assume the plywood would have to be fastened using a powder gun, right?
And finally what about this crazy idea.... just spread out some sort of skim coat of cement to even out the concrete, seal it and apply the carpet pads directly?
Again, this basement seems to only get water in record rainfall incidents, and even then less than 1/2" of water... would it be ok for the plywood to just sop that up since it's pressure treated, and we can temporarily remove the carpet tile in the affected area to let the plywood dry out.
Any advice is welcome,.. .thanks guys.