# Basement Subfloor



## sbcontracting (Apr 22, 2010)

Hey there.

I am installing 3/4" T&G ply over top of delta FL for a basement. I will be fastening the ply down to the cement with either hilti or tapcon (depending if the hilti nails stick or not). 

Would you put the subfloor down first in the open space and then build the (non-structural) walls over top of it? That would be obviously the easiest and fastest.

I'm just wondering if the ply subfloor would ultimately sag the 1/4" space that the delta membrane takes up under the walls. I doubt it, and Delta claims that their product (if it's under plywood) can support the weight.

Just curious what others have done.

Thanks, Mike


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## greg24k (May 19, 2007)

sbcontracting said:


> Hey there.
> 
> I am installing 3/4" T&G ply over top of delta FL for a basement. I will be fastening the ply down to the cement with either hilti or tapcon (depending if the hilti nails stick or not).
> 
> ...


I am not sure about Delta, I have been using Superseal and Compressive Strength of that is 7800 psf , and dimple height is 1/8". With that you don't need to use plywood, the floor (wood or carpet) is installed right over it.


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## sbcontracting (Apr 22, 2010)

Hmm.. I'll chk out superseal, 5800 psf for Delta.

Plywood might be overkill. Initially HO wanted a zero-squeak engineered HW floor. They have since gone with an engineered laminate with an MDF core, so the creaking will be minimal without stapling/gluing. Hardwood isnt an option at this point.

ps - this is NOT the same house with the mould issue 

Mike.


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## katoman (Apr 26, 2009)

How do you plan on levelling the floor?


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## sbcontracting (Apr 22, 2010)

I wasn't planning on leveling it. The 3/4" plywood would smooth out some of the more drastic non-level elements in the floor - but it's not too bad to begin with. 

The 'engineered hardwood' HO has settled with is 1 mil spruce veneer as a base, with 3/8 mdf (or so), with 2mil Oak HW on the top. So it will behave more like laminate flooring, as far as squeaks go. I'm not too worried about an unlevel floor producing too much in the way of squeaks on this floor.

And this is the reason I'm seriously considering just the superseal. It's pricier than Delta, but I like the lower profile. Less likelihood of producing a spongy floor. I hate that feeling on laminate/eng hw.


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## katoman (Apr 26, 2009)

Here's how I do a bsmt. floor. Keep in mind today these "basements" are becoming part of the living space in a home. Not just somewhere to dump the kids.

Lay down tarpaper, strap with 5/8" x 2" plywood strips. Shim as you go to create a level floor. Then 5/8" T&G plywood. If there is ever a leak into the bsmt. it will still flow to the drain.

This also allows the installation of any type of flooring. 

Here's a pic of the last one I did.


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## sbcontracting (Apr 22, 2010)

Kato,

My basement at home was done pretty well like that. I gutted it, and most of the strapping was rotted or mouldy. It was about 30 yrs old. ... but still- I don't know if i like that setup - other than it's the ideal way to level the floor.

Nice basement, btw


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## sbcontracting (Apr 22, 2010)

Update: HO's selected an engineered floor I've decided to just recommend to the HO's the Superseal after looking at the product, and put the floor right over top of that.

Greg, with the Superseal, do you put a floor underlay over top of it and under the floor? 

The floor that the HO selected also must come with an approved underlay in order to have the warranty on the floor. (!). Most of the approved underlays are too spongy or too expensive.

The one that I'm going to probably go with is 2mm cork.


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