I need some advice/suggestions for what type of sub-floor to use for our basement. We remodeled it 6-7 years ago, installed a perimeter sump/drain tile system and installed wall to wall carpet/pad directly on the concrete floor. We would notice dampness at certain times of the year but it would always dry out. A couple of week ago, I noticed the carpet was really saturated/soaked in the middle of the room. Perimeter was dry and sump system worked fine. I believe this is the result of excessive condensation built-up. We have never used a dehumidifier but will in the future. We decided to go ahead and replace the carpet but thought it best to install a sub-floor to ensure this does not happen again.
Has anyone used the Dri-core system?
There is an article on the FHB.com site that recommends using rigid insulation on the floor with two layers of plywood over it. Has anyone used that method? Seems like you would need room for air to move under the floor and allow any condensation to evaporate. Not sure how that would work with this system.
Any advice or suggestion are welcome.
Cheers,
Velo
Replies
If condensation is the cause of your moisture problem than the foam under subfloor method will solve it when combined with good insulation on the crete walls too. Quality insulation eliminates the dewpoint contact between damp warm air and cool concrete surface.
But if you do not control that entire situation and leave a possibility for condenstaion or if the source of the moisture is leaks or hydrostatic pressure, then you need the dricore system or another like it.
There are other types of dimple mat in 4-5 foot wide rolls that can be used under a couple sheets of ply to provide the capillary space.
But the dricore simplifies the method and installation.
The reason for the double layer of ply is to reduce or eliminate lifting and wandering of the material since it does not attach top the concrete. I think I would still lay another 3/8" or 1/2" of underlayment glued to the dricore base.
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The traditional way to do this is to lay sleepers on the floor, and attach subfloor to the sleepers as it would be attached to joists on an upper storey. This is labour intensive and requires skill in the use of a table saw and transit or laser level. But, it provides the best job as it is the only way you can get a level finish floor: by tailoring the sleepers to compensate for the drainage slope of the basement floor. (Sleepers should be screwed down with Tap-Cons¯ and glued with PL Premium¯.)
You cannot accomplish this with Dri-Core¯ or any similar system unless you first level the surface of the slab itself with an SLC or patching mortar...which is not a good idea because you will eliminate the drainage slope in so doing. All basement slabs should slope towards the code-required floor drain. Thus, the top surface of the Dri-Core¯ will be parallel to the slab, and, if the slab was properly finished, that won't be level.
That said, I have used Dri-core¯ in a basement remod which called for the installation of ceramic tile in two small areas (a bathroom and a kitchen). The advantage of using a product like Dri-Core¯ in this kind of application is that you wind up with a lower transition height between the glue-down carpet elsewhere and the ceramic tile on he subfloor. Of course economy is also an element; Dri-Core¯ is quick to install, even though it's much more expensive per square foot than sleepers plus ply. When you're paying for labour, this has to be considered.
Final caveat: Dri-Core and other similar material is made from OSB which soaks up water like a sponge. If your basement even gets a half-inch of water in it--say, that sump pump fails while you're on vacation some spring--all the Dri-Core¯ will be ruined.
This won't happen to a solid-lumber sleeper, even if it's made of a non-rot-resistant species such as spruce. It will dry out and be fine afterwards. (If you're really worried about the sleepers rotting, use something like hemlock or cedar. You do not need to use PT. That is a myth propagated by the PT lumber companies.)
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