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Best way to insulate my cement basement floor (above slab)?

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Posted by: from Edmonton
4/3/2021 at 2:36:31 AM

I just moved into a house with an unfinished basement that I'd like to begin the process of finishing. I've decided against the subfloor panels (like DriCore, Barrier, etc.), because after talking to their representatives, they do not recommend their panels as the finished flooring I have needs to be nailed/stapled down.

I've decided on the rigid foam panels method of insulating above my cement slab, but I've seen two different methods, and I can't get a straight answer on which is "better":

1. Using pressure treated wood in a "sleeper system" to essentially frame my cement slab, then placing the rigid foam panels in between the sleepers/joists (much like insulating in between the framed studs on a wall), then fastening a thick enough layer of plywood subfloor to the sleepers, that I could then staple/nail my finished flooring to.

2. Create an entire "floating" layer of rigid foam panels directly over top my cement slab, no sleepers or joists, then seal all the joints between the panels with Tuck Tape, then a "floating" layer of plywood subfloor, followed by a second layer of plywood subfloor, which is screwed down to the first layer of subfloor (but ensuring the screws aren't so long that they penetrate the foam panels), and then staple/nail my finished flooring to that "two layer" plywood subfloor.

Both of these methods of course, I would use a vapor barrier on top of the cement slab before laying any sleepers or foam panels on it (unless the foam panels already have a "vapor barrier layer/coating, which some have). In my head, the "floating" layer of foam panels seems more logical, as it is a continual layer of insulation, and isn't "broken up" by the sleepers/joists (even if they are pressure treated). However, I can't get a clear answer either way. What do you think is the best way to go here?

Thanks!

REPLIES (3)
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Date/Time4/3/2021 at 8:07:52 AM

These two systems that you propose seem like a lot of work and expense, it is a basement after all. I would use a fast set glue (PL fast tack) and just glue the flooring to the concrete. Alternatively, however more expensive, you could tapcon sheets of plywood down with 6 mm poly underneath and place the floor on top of the plywood.

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Armand from AQC Renovations in Falconbridge
Date/Time4/3/2021 at 8:27:11 AM

The best way to go is to put the rigid foam board down onto the concrete, tuck the seams, put a layer of 5/8 or 3/4 inch plywood over top then Install Tapcon or ucan every 12 inches through the plywood which will go through the foam and into the concrete. This will pull everything tight & prevent movement. You should then be able to install any flooring. You do not want to install vapor barrier. The foam board has its own barrier.

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Date/Time4/3/2021 at 9:08:56 AM

I would strongly suggest sticking with the dricore. It likely to be cheaper and more efficient. Then cover the panels with 4x8 sheets of 3/8 plywood. Just make sure to cover all of the seams and stagger your boards

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