Existing basement subfloor

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Posted by: from Waterdown
1/23/2017 at 12:41:49 PM

I'm renovating my basement that was finished by the previous owner. The house is around 25 years old.

Half of the basement floor already has a solid subfloor. It consists of 1x2 strapping with 1x12 inch Styrofoam, topped with 3/8 plywood.

It does not appear to have a plastic vapor barrier between the concrete floor and the strapping/Styrofoam.

My question, is this fine to keep as the subfloor? Or should it be removed and replaced with a subfloor that includes the vapor barrier?

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Date/Time1/23/2017 at 1:10:20 PM

In my professional opinion I would rip up the whole floor and install vapour barrier directly on the concrete slab. Any joints are to be sealed tightly with an overlap so no moisture can get out and create mold.

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Date/Time1/23/2017 at 3:03:00 PM

Hi Mark,

I personally would remove all the existing subfloor if it was my house. Then you can inspect the foundation and concrete floor. You can then put a proper subfloor in with 6 mil vapor barrier. 3/8 plywood is not too code for any floor and should not be used again. 5/8 tongue and groove is what you need to put down for a subfloor plywood. Or you can buy pre manufactured 2-foot by 2-foot subfloor panels at your local Building Center. If you are going to put carpeting and tiling for flooring you could delete the subfloor all together and use a carpet underpad that has a built-in vapor barrier and you could install in floor heat under tiles.

Jeff from all in renovations.

Calgary Alberta

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Chris from C&M Construction in Edmonton
Date/Time1/23/2017 at 5:32:16 PM

Removal is the best approach. Leaving that as is would be asking for trouble do the road. Of course concrete by nature loves moisture. This is the reason when framing interior walls. All wood material in contact with concrete needs to be treated (green or other new various colors). Having a barrier will help prevent mold issues as others have stated.

Chris from C&M Construction


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Mark in Waterdown
Date/Time1/23/2017 at 5:43:15 PM

Thanks for the replies. That's what I thought.

I'm planning on finishing the floor with vinyl planks. What's the recommended subfloor/underlay?

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