# How to do plywood underlayment for sheet vinyl



## rusty baker (Feb 13, 2009)

Do not use screws in underlayment for vinyl. It will make puckers which will show through. 1/4" underlayment grade plywood(not luan) ahould be stapled (9/16") every 4"-6" in the field and every 1"-2" along the edges. I have always butted the sheets tight, some installers don't. Then use a cementious based patch on the seams. The door casings should be undercut and trim should be put over all the other edges. It doesn;t matter where the seams are in the underlayment, in a small bathroom, since the underlayment is only fastened to the subfloor. And do NOT glue down the underlayment. There is no need to skim the whole floor with Ardex.


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## ken24 (Oct 14, 2011)

Are you saying to use staples for fastening the 3/8 plywood underlayment?

Do you mean a medium crown construction power stapler? like about a half-inch wide or so?

Should I avoid hitting the joists beneath the 3/4 subfloor? Which would be hard to do since many are sistered w/extra joist.


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## rusty baker (Feb 13, 2009)

Use 1/4" plywood not 3/8" for underlayment. The 9/16" staples (1/4" or 18 guage) staples will not reach thru the subfloor and into the joists.


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## ken24 (Oct 14, 2011)

Rusty,

I already bought the 3/8 ply and it will bring the vinyl level w/the hardwood in the hallway.

Just to clarify: the stapler you are talking about is an 18 ga. narrow crown stapler and shoots a staple with a 1/4 crown which is 9/16 in length. Correct? 

I assume the staple will go beneath the surface a bit and later be covered w/ardex?

thanks,

Ken


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## rusty baker (Feb 13, 2009)

If the compressor is set right the staple will be set slightly below the top, but not enough to damage the top ply. Why do you want to skimcoat the plywood? Won't hurt anything but, It isn't necessary.


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## Floor Doc (May 29, 2010)

Just flash the joints on the plywood .


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## Gary in WA (Mar 11, 2009)

Just to back-up what has been posted already: http://www.apawood.org/pablog/index...tion-of-Plywood-Underlayment-in-Floor-Systems

http://www.apa-europe.org/Languages/English/PDF/R340G.pdf

Gary


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## ken24 (Oct 14, 2011)

Is it necessary that the fasteners be rust resistant? Or is water/moisture much of an issue?

I'm not familiar w/the term "flash the joints" 

Just so I understand, I should use 1/4" ply and use a narrow crown (1/4") finish stapler gun shooting 9/16 " long staples. Is that correct?

My vinyl installer said he likes to use 1/4" luan at home depot for about $10 a sheet as a great underlayment.


Thanks for the input


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## rusty baker (Feb 13, 2009)

luan has voids in the plys. It is not an accepted underlayment. "flash" just means to fill the joints with a cementious base filler to make them smooth. Yes, galvanized staples are best. The moisture from the adhesive can make plain staples rust and the rust can stain thru the vinyl.


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## ken24 (Oct 14, 2011)

My house was built in 1948. My kitchen also has a vinyl floor and it has the original 3/8 ply under layment; I think they nailed it down back then. 
But still seems to be in fair shape.

Anyway, I feel compelled to use 3/8 ply for the bathroom as well since that's what was in there before and it will bring the hallway wood floor flush w/ the bathroom vinyl floor.

So, for 3/8 ply what fastener would you recomend? And what nailing schedule?

thanks, Ken


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## Bud Cline (Mar 12, 2006)

Just curious...
Are you confusing subfloor with underlayment?

In a house that old you probably wouldn't have a sheet-style subfloor but one never knows about California stuff.


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## ken24 (Oct 14, 2011)

No confusion; The original subfloor was 1 x8's on the diagonal and that's what is in the kitchen now w/ a 3/8 ply as vinyl underlayment.

But because I had a lot of water damage in the bathroom from a leaking shower for many years, I replaced the original subfloor there w/3/4 ply and now I am getting ready to install the underlayment for vinyl.


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## Mark Potter (Aug 19, 2011)

Just for clarification this is what every one is talking about for vinyl prep.










Total soup to nuts on how to do on this "correctly"

http://www.extremehowto.com/xh/article.asp?article_id=60919


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## ken24 (Oct 14, 2011)

Mark,

I took a peek at the article; it looks great! I'm looking fwd to reading it on monday

Thanks so much,

Ken


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## Mark Potter (Aug 19, 2011)

ken24 said:


> Mark,
> 
> I took a peek at the article; it looks great! I'm looking fwd to reading it on monday
> 
> ...


NP Ken sometimes it gets confusing with every one trying to explain step by step and it's a big job for a DYI'r good luck we'll be here for more questions if you need it


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## rusty baker (Feb 13, 2009)

I disagree with some of the stuff on that, but what do I know. I've only been installing vinyl for 38 years. :whistling2:


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## Mark Potter (Aug 19, 2011)

rusty baker said:


> I disagree with some of the stuff on that, but what do I know. I've only been installing vinyl for 38 years. :whistling2:


?.. How's that what parts may I ask


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## rusty baker (Feb 13, 2009)

I already posted the right way to do it, don't plan on repeating myself.


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## Mark Potter (Aug 19, 2011)

rusty baker said:


> I already posted the right way to do it, don't plan on repeating myself.


Oh ok well.. That DIY link wasn't directed to insult anyone's flooring experience here.


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## ken24 (Oct 14, 2011)

Thanks for all the info thus far; My research is almost complete.

I will be going with 3/8 ply for the underlayment which will be fastened to 3/4 ply subfloor. 

Everyone and the article suggests using staples; OK, but which one for the depth of these two plys?

I'm thinking that I should use a 16 ga. standard crown staple gun (1/2" crown) with a fastener length of say 3/4" to 1"

Thanks for your suggestions.


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## ken24 (Oct 14, 2011)

Rusty Baker, thanks for the info

I know you said to use 1/4 ply for the underlayment but I decided to reinstall what I removed and what's in the kitchen which is 3/8

*Questions*

1. Will the 1/4 crown stapler work for the 3/8 ply driven into 3/4 ply sub floor?

2. How long should staples be?

Thanks flooraholic


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## ken24 (Oct 14, 2011)

Rusty Baker, 

I know you said to use 1/4 ply for the underlayment but I decided to reinstall what I removed and what's in the kitchen which is 3/8

Questions

1. Will the 1/4 crown stapler work for the 3/8 ply driven into 3/4 ply sub floor?

2. How long should staples be?

Thanks


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## rusty baker (Feb 13, 2009)

I would think it would hold, but have never used 3/8 for underlayment. 1/4" is standard, and thats all I've ever used. Flooring stores only use 1/4, because that is what the vinyl mills want used for warranty.


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