With DriCore, why is the 1/4 inch gap around the perimeter necessary?
Just watched the install guide for Dricore. I’m finishing my basement. Right now it’s bare concrete. It says in the video to leave a 1/4 inch gap around the perimeter. However it doesn’t give a reason why. Here is what I was originally planning on doing. I have true foam type two rigid adhered to the concrete walls with seams taped and spray foam to fill in the corners and bigger gaps. Next the plan was the install the dricore tight against the foam. exterior walls are to be studded up on top of the dricore 24′ oc with r20 batts between the studs. Then vapor barrier over the batts on the warm side to complete the system. If I leave that 1/4 inch gap of exposed concrete to “breathe” essentially between my wall and insulation am I not just asking for trouble? Or will I cause more problems by NOT leaving the 1/4 inch gap?
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Replies
Mark,
You should probably direct your question to a technical expert at DriCore. I can imagine two reasons:
1. Leaving room for possible expansion, or
2. A belief that an air connection between the air gap under the DriCore panels and the air in the basement will allow moisture from the concrete to dry toward the interior -- an unlikely drying mechanism.
Mark,
What did you ultimately decide to do? Did you leave the gap?
Thanks.
i have the same question
If Martin's Reason #1 (allowing for expansion of the tiles) is correct, and I also think that's the most likely reason, then you can seal around it to the walls with a flexible air barrier. That "flexible air barrier" could just be a continuous piece of wide flashing tape hidden with cove base, or for something more durable use some PVC shower liner or 20 mil tape. All you would need is something that is flexible to allow the tiles to expand/contract a little.
If there is a real reason the manufacturer has for a drying path such as Martin's Reason #2, then you'd need to connect that under-tile air space with an air space behind the wall insulation. I'm not sure what that would really accomplish though.
I suppose another option would be to put some open cell weatherstripping in the perimeter gap. This would allow for expansion/contraction of the tiles, and would also allow for some slow/limited air exchange too. This would be something of a happy medium if you can't just use a flexible air seal such as I described for Martin's Reason #1.
Bill
Hi Bill
I contacted the supplier Dricore and also similar vendors and really i did not got a satisfactory answer....They all insist on leaving the 1/4" for expansion/contraction, i understand that and agree .However they also insist to have a connectivity between basement air and below subfloor through the 1/4" space to let the concrete breath to remove moisture ...that i don't understand why? If you have that over the years continuous flow of vapor from concrete to the basement that will ruin everything. Do you agree?
They are probably concerned that things will get overly wet under the tiles without some ventilation. If they are specifying that ventilation as a requirement, then you'll have to work with it. I suppose if you want to get creative, you could add a perimeter vent channel and vent it to outside at the corners with PVC pipe.
A very small amount of airflow through a 1/4" gap is unlikely to really do much in terms of causing problems in your basement.
Bill