# Plywood Subfloor - does it need gaps for expansion?



## oh'mike (Sep 18, 2009)

Typologically it is butted tight---i suggest that more stapling is needed at those edges----


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## joecaption (Nov 30, 2011)

How did they fasten and what's the pattern?


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## crayola110 (Aug 23, 2012)

They only did the plywood around kitchen so they're just butted against each other. 
It's fastened with screws whereever the joists is but not on edges of the plywood


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## oh'mike (Sep 18, 2009)

You better watch those guys---underlayment is typically screwed or stapled every eight to ten inches--3 to 4 inches at the seams, avoiding the floor joists.

I might be missing something---this is underlayment over an existing subfloor,correct?


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## joecaption (Nov 30, 2011)

I also never screw down under layman.
The old boards under it should have been screwed down but screwing down underlayment will cause raised area where the screws went in.
I fasten every 4" on the edges and 6 to 8"in the field.
I would have used a pneumatic staple gun with narrow crown staples. Underlayment nails are also acceptable. 
Underlayment is never attach to the joist. The whole idea is to get 100% contact with what's below it. So attaching between the joist pulls it down between the gaps where the flooring sags between the joist.


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## crayola110 (Aug 23, 2012)

oh'mike said:


> I might be missing something---this is underlayment over an existing subfloor,correct?


Yes I was unclear in last post: it's 3/8 plywood flat over diagonal boards., which are over the joists. And they did NAIL it down, not screw it down. I was writing that quickly from my phone.

It looks like they nailed it down the line of where the screws are. The thing is they already put cabinets over it so it would be impossible to fix now.

joe, I notice there's not nails along edges. So your saying around the edges they should put those nails down correct? I'm guessing this is why it's popping up by 1/8 inch where the edge of one plywood touches another edge of a plywood


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## joecaption (Nov 30, 2011)

The edges are the most important area. That's why it should have nailed every 4".


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## crayola110 (Aug 23, 2012)

Thanks so much joe, i'll tell the contractor when I talk to him later and ask him whats up.


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## JazMan (Feb 17, 2007)

> i'll tell the contractor when I talk to him later and ask him whats up.


I love it when the customer has to tell the handyman how to do things. 

3/8" over plank subfloor? Well, that's wrong too. 

Read the direction for your vinyl flooring to see how to handle the seams of the underlayment, after they're properly fastened of course. 

Jaz


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## crayola110 (Aug 23, 2012)

JazMan said:


> I love it when the customer has to tell the handyman how to do things.
> 
> 3/8" over plank subfloor? Well, that's wrong too.
> 
> ...


 He is a contractor...I dunno if that helps much here in California or as it seems it's just filling out some paper work and getting liability insurance/bond.

What is wrong with 3/8 over the plank subfloor?

the directions say this regarding wood subfloor: *

Wood subfloors :​* Including Hardwoods, Plywood, OSB, Luan,​ Par ticleboard & Chipboard are approved, but​must be sturdy, flat and have little flexibility."

thanks


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## joecaption (Nov 30, 2011)

And where are you getting that info?
Most of it is wrong.
Particle board gets wet once and it turns to oat meal, it also can swell up from just a high moisture content from something like no vapor barrier in a crawl space.
Luan has not been an excepted subflooring for may years because of voids in the core, causing glues to let go, and staining through the flooring.
Linoleum will mirror any flaws in the subfloor below, use OSB and your floor will look like a bumpy back road in no time.


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## JazMan (Feb 17, 2007)

In the end 3/8" over planks might be good enough in this case if: The planks are in excellent condition. Generally you'd want to use minimum 1/2" over planks if they are perfectly flat. 

I'm pretty sure the instruction are more detailed than that. Specifically which floor will you be installing?

Jaz


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## joecaption (Nov 30, 2011)

Plank floor almost always have slight cupping, flex between the board, small differences in thickness of each board.
A thin plywood will just follow the flaws in the floor below.


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## crayola110 (Aug 23, 2012)

joecaption said:


> And where are you getting that info?
> Most of it is wrong.
> .


I got it from the manufacturer instruction manual: Allure
http://www.homedepot.com/catalog/pdfImages/7f/7f23b8b8-723e-4a48-be74-a36c7051994d.pdf

(I've used their lower grade vinyl plank flooring in rentals and it's held up pretty well. I've installed over cement and old linoleum with good results as long as the floor beneath is flat. I have seen some knicks from the cement show up through the regular Allure which is 3 mm but this one is commercial grade and 5mm.)

This is for their "Ultra" version which has a lifetime warranty and 10 year commercial warranty. The Ultra which I'm going to install I've taken hammers, key, blades etc to and it's held up with some small scratches that can kind of be buffed off with a scotchbright sponge. It is 100% water proof as it's just vinyl.

I do agree joe, that most of that material is no good, but it's approved according to Allure. 

Jaz, is it worth bringing the 3/8 ply all out? Supposedly grade A. The diagonal planks seemed in sound condition


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## Gary in WA (Mar 11, 2009)

IMO, walk on it between joists, if it deflects- it won't get any stronger.... all plywood requires end gaps for expansion as it changes with RH from seasons- roof/wall sheathing, subfloor/underlayments; http://www.google.com/url?sa=t&rct=...sg=AFQjCNENoqBzUtmt80KjT8zGvW-cKEftFQ&cad=rja

Gary


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## rusty baker (Feb 13, 2009)

Ok. To do it right, you need 1/2" plywood over the planks. And then for a smooth surface for the vinyl, you need 1/4" underlayment grade plywood stapled with narrow gauge staples, every 4" to 6" in the field and every 2" to 4" on the edges. The ends needs to be staggered and I always filled the seams with cementious based fill, although some installers don't. Might as well do it by the book, if you are going to do it. I am Armstrong vinyl certified (went to their vinyl/lino school) and have been installing since 1973. And you do need a small gap between the plywood and the wall. All wood expands and contracts.


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## Gary in WA (Mar 11, 2009)

NA

Gary


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## mako1 (Jan 7, 2014)

I do use lots of Allure.I have put in 4 floors of it this week.We use 5/8 T&G under(and PL400 on the joists if we have to remove the existing floor) it if the floors are iffy..Pad then lay the floor.I have put lots of it over 3/4 wood floors where the floor were in good condition and we put 30# felt and then the Allure Trafficmaster and the floors were fine assuming there is a good floor under.Some of the clients don't like the extra pad under them that's why we use the paper..Many of them have been fine for years.I would however follow the manufacters suggestions.


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## mako1 (Jan 7, 2014)

Joe is right on about this but there are ways to help the problem if you must use the product on substandard floor.On a budget or a rental.If your subfloor has a raised edge here and there you can take a piece of 30# felt about 6" wide and staple it to the raised seam in the affected area and buld it up to where the tile lays good.I don't recommend this but thought I would throw it out there for the folks that are going to save a dime either way.


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