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Basement Slab floating subfloor

Abindra | Posted in General Questions on


I’m in Ontario, Zone 6B.  Based on what I’ve seen here, I’m thinking of
concrete> 3/4″ poly faced EPS foam taped at seams > 1/2″ plywood > flooring.

I think this is the minimum insulation for my area. And I’m trying to minimize height. 

I’ve seen a very old post elsewhere that suggested that foam and plywood could be attached using foam adhesive, foam to concrete and plywood to foam.  (rather than using tapcons or two layers of plywood).  Would that work?

Is there any benefit to using tongue & groove plywood rather than regular plywood? If I use regular plywood, do I need to leave 1/8″ gaps between the sheets?

Please let me know what you think.

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  1. user-2310254 | | #1

    I'll give your post a bump. FWIW. If Dana provided a workable plan that fits your climate on another website, I wouldn't overthink this.

  2. Abindra | | #2

    Thanks. It was a very old post from 2010. Not sure it can still be relied on.

    Using foam glue rather than tapcons seems like an excellent way to make installation easier, but only if it works.

    Nothing survives a flood, but I'm wondering how this setup handles small leaks. As an example, I had a humidifier leak a gallon of water under my old floor. Would foam and plywood dry itself out up through the flooring?

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