# Carpentry: PT Plywood subfloor - Putting flooring on it?



## Just Bill (Dec 21, 2008)

Not sure I understand. Framing for any outside structure if often done with PT wood, but the subfloor(plywood, OSB) is not necessarily PT, and will accept most any floor covering. Even if it is PT plywood, an underlayment plywood can be installed to go with the vinyl.

This is a 'DIY' website, not a 'what did my contractor do' website.


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## Jeffries (Jun 18, 2010)

Just Bill said:


> Not sure I understand. Framing for any outside structure if often done with PT wood, but the subfloor(plywood, OSB) is not necessarily PT, and will accept most any floor covering. Even if it is PT plywood, an underlayment plywood can be installed to go with the vinyl.
> 
> This is a 'DIY' website, not a 'what did my contractor do' website.


Just Bill
Thank you for your reply and I do know this is a DIY website. We are installing the flooring ourselves and were wondering if it would adhere to the PT wood.


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## DangerMouse (Jul 17, 2008)

Yup, just put a thin plywood subfloor down and vinyl away!

DM


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## JazMan (Feb 17, 2007)

Not so fast.

PT plywood should not be used indoors, I wonder why they did that? I'm not sure if there's any health hazard with the new chemical used in PT, but I do know the moisture content is off the chart. It may be OK to install an underlayment and then vinyl after the PT dries? I wouldn't do it, but you can check with the manufacturer on that. Is this new PT the subfloor or was there a subfloor and this is the underlayment? 

OK, now my question. Why vinyl in a sun room? It's not what I'd consider an appropriate flooring in that kind of room. 

Jaz


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## firehawkmph (Dec 12, 2009)

Also one other thought, if you find out it's ok to put some kind of underlayment over the PT plywood, make sure you use fasteners that are approved for contact with PT wood. Usually means hot dipped galvanized or epoxy coated like the newer deck screws. The boxes are starting to say 'safe for use with AQ', that's the new treatment in PT wood.
Mike Hawkins


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## Jeffries (Jun 18, 2010)

firehawkmph said:


> Also one other thought, if you find out it's ok to put some kind of underlayment over the PT plywood, make sure you use fasteners that are approved for contact with PT wood. Usually means hot dipped galvanized or epoxy coated like the newer deck screws. The boxes are starting to say 'safe for use with AQ', that's the new treatment in PT wood.
> Mike Hawkins


Thanks so much for the info on the right screws to use. That's what we'll do. :thumbsup: Jeffries


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## Jeffries (Jun 18, 2010)

*Carpentry*



JazMan said:


> Not so fast.
> 
> PT plywood should not be used indoors, I wonder why they did that? I'm not sure if there's any health hazard with the new chemical used in PT, but I do know the moisture content is off the chart. It may be OK to install an underlayment and then vinyl after the PT dries? I wouldn't do it, but you can check with the manufacturer on that. Is this new PT the subfloor or was there a subfloor and this is the underlayment?
> 
> ...


Jaz, we are putting a plywood subfloor over this P.T. wood floor. We are also wondering why P.T. wood was used. I wasn't sure what kind of flooring to put over the subfloor and thought vinyl would be OK. If that's not considered appropriate what would you suggest?
Jeffries


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## Flinnad (3 mo ago)

Just Bill said:


> Not sure I understand. Framing for any outside structure if often done with PT wood, but the subfloor(plywood, OSB) is not necessarily PT, and will accept most any floor covering. Even if it is PT plywood, an underlayment plywood can be installed to go with the vinyl.
> 
> This is a 'DIY' website, not a 'what did my contractor do' website.


What thickness should the additional plywood be?


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## Flinnad (3 mo ago)

Flinnad said:


> What thickness should the additional plywood be?


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## chandler48 (Jun 5, 2017)

Your total flooring thickness should be about 1 1/4", depending on what final flooring is. The thread is 2 years old. It is always best to start your own thread and refer back to the old one if necessary. Give us the details of your project and we can help better.


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