Basement Floor Underlayment foam or no foam
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I am installing a floating cork floor on my basement slab and have decided to use a dimpled underlayment. One product instruction says to maintain a gap at the vertical edges, the other says to foam the edges.
http://www.superseal.ca/NewPDFs/All_In_One_Subfloor1.pdf
http://www.cosella-dorken.com/bvf-ca-en/pdf/install_instructions/DELTA-FL_install_inst.pdf
I’m leaning towards the foam for the same reason I foamed around the XPS against the concrete walls – to avoid the conditioned interior air from contacting the concrete.
Foam or not to foam…?
thank you
Frank
Seattle, Marine Zone 4
2 inch foam against walls and foam insulation under slab
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Replies
Outside footing drain burritto and mirror drain installed
What phenomenon are you concerned about? ie, what are you trying to avoid? Is not the cork very porous? BTW: In the pic above, I don't see a porous mat over the pipe. I believe one is usually used to keep dirt out of the drain pipe.
I'm concerned about moisture migrating through the slab and damaging my flooring. During the summer months, I'm concerned about the warmer, humid air condensing on the cooler concrete and damaging my flooring.
Ive done two areas with the plastic taped to the floor and after 24 hrs, no moisture was present.
The flooring directions say lay down a 6 mil barrier. Ive also read it's best to let the concrete dry to the interior. Seems the dimple product accomplishes both.
Frank,
If you have a continuous layer of rigid foam under your slab, and if you have no history of water entry or dampness, you are probably OK no matter how you detail the perimeter of your dimple mat.
I suggest that you install the dimple mat following the directions of the manufacturer of the product you choose to install.
Frank,
My experience leads me to suggest application of a vapor closed, liquid applied membrane to the top surface of your concrete slab. After that, don't worry about what you do at the joints between the underlayment squares.
Concrete has about the same equilibrium moisture content vs. relative humidity characteristics as wood, so, it will capture and release water vapor as RH in your basement changes from Summer to Winter. The problem is, its thick, so, it can capture and release quite a bit over time. The membrane will significantly reduce this movement.
Foster
Thanks for the feedback. It had been recommended to me to seal the concrete with a product like Super Seal....but what about letting the concrete breath/dry to the interior? And if I seal it and prevent the moisture from migrating to the surface, would I even need a dimple product?