Plywood Gaps, Expansion Problems? What's the real reason???

[Willy]

OK it has got me thinking on plywood gaps on installation. Is it realy for expansion of the plywood? I don't think the plywood will expand anymore than the wood it is nailed to. Now I might be wrong on this plywood is manufactured wood at a pretty set dryness and cross grained ect so it should not shrink much after it is made. Now Kilm Dried wood is a different story. It can be wet due to winter storage or some grades of 2/By wood it not realy cured yet and still part green. So it can and will shrink some as it drys out later after nailed in place. So would it be wrong to think that the little gaps they want you to put in the plywood sheets are for contraction of the wood it is nailed to so the sheet won't buckel up some when the wood drys real good later?? I just can't see the studs and plywood each moving that much different due to expansion being nailed together.
OK what is the real reason for the gaps in plywood and if it is expansion due to heat do you not gap it when the wood is hot and what about the rest of the wood expanding and contracting? I do know wood can shrink/expand if it is dry/wet. Mark

[Willy]

The guy who put in my Oak Floors in my home wanted the oak kept in the house for at least a week so it would be the same moisture  as the rest of the place. He told me it makes a better floor as the wood would not shrink some as it dried out getting warm and open some gaps. I also heated the place with wood and that lowed the humidity so I had to put water on the water stove like I would during normal winters. I had not moved in yet but was warming up the house cause it was winter. Mark

[John Raabe]

Plywood, since it is a sheet product expands and contracts as it gives off or takes on moisture. It also moves a bit with temperature. If you put it down tight and dry it may buckle and bulge if the moisture content goes up. You want to give it room to "breathe" at the edges (about 1/8").

Framing lumber does this too but over smaller dimensions.

[MikeT]

I have many gaps on my place that are larger than 1/4".  They were ones that were fit in or were cut on the wrong side of the mark.  I hope that passes muster on the other side of extremes.

mt

[Willy]

I have many gaps on my place that are larger than 1/4".  They were ones that were fit in or were cut on the wrong side of the mark.  I hope that passes muster on the other side of extremes.

mt

Well I am lucky I only have one sheet of plywood to cut in haft to do my floor, also hard to gap 2 sides of T&G. The roof is a different story but it won't be bad I just hope all the cuts end up over the rafters and no waste! I figured my over hangs to use up any waste, I only lose a small strip at the ridge. Mark

[ScottA]

Something I discovered is that T&G sheets aren't 4x8 but more like 47 1/2" x 95 7/8". Not that big a deal till you realise you lost 2" across a 16' floor.

[Willy]

Something I discovered is that T&G sheets aren't 4x8 but more like 47 1/2" x 95 7/8". Not that big a deal till you realise you lost 2" across a 16' floor.

You got ripped off on your plywood. All 3 types of mine are 4X8 except the 4X9 siding ones. I will have to figure cutting off 1/4" to 3/8" at the end of my cabin. I just went out and measured them. Mark

[Redoverfarm]

Scott same thing with my T&G advantex subfloor.  You are OK until the last sheet.  Standard ply w/o T&G is true I think.

[Willy]

Scott same thing with my T&G advantex subfloor.  You are OK until the last sheet.  Standard ply w/o T&G is true I think.

Did some checking and both dimentions are sold in plywood. I would have been bummed when I got to the end or side of my building and had to add a couple inches of plywood. Mark

[Redoverfarm]

Mark actually it is 4'X8' but there is a tounge and a groove so your finished surface (part that is seen) is less. Not right IMO but a 2X4 is not a 2X4 either. You have to compensate with a little more than a half sheet somewhere whether it be in the middle or the end.

[Willy]

Mark actually it is 4'X8' but there is a tounge and a groove so your finished surface (part that is seen) is less. Not right IMO but a 2X4 is not a 2X4 either. You have to compensate with a little more than a half sheet somewhere whether it be in the middle or the end.

No my T&G is wider than all the other 4X8 full size sheets. On the 3/4" T&G there is a little more tounge designed to go into the next sheet so when together it looks like 48" on the seams and a full 8' length . It is realy 48 1/4" wide if you count the tounge to. They do make the narrower and shorter plywood also. 2X4s are different but if you buy a 8 ft long one it is 8 ft unless you buy a stud. The before Milling size is what they discribe in that wood unless you buy full dimention wood. Mark

[MountainDon]

So it would seem to vary with brand, perhaps. Next time I am near a stack of T&G sheet goods I'll have to measure them.

[ScottA]

That's all well and good but I wish I had known all this before I framed the floor. It all worked out though I added 1/8" for expansion which got back 1/2" then split the difference on each side. Still was kinda sucky having a 3/4 gap on each side of the floor under the wall. Had I known I would have made my cabin 1 1/2" narrower.

[Willy]

So it would seem to vary with brand, perhaps. Next time I am near a stack of T&G sheet goods I'll have to measure them.

Checking on a Googal Search I could find where plywood is made in standard 4X8 sheets then the grouve is cut into it for T&G. I also found sites selling plywood that was a few like 30 & 40mm bigger than the other sizes they sold. SO I went out again and measured my plywood. My 7/16" CDX sheeting is excactly 48" x 96", my 3/4" T&G(with tounge) is 48 3/8" x 96" and my siding(with over lap) is 48 3/4" X 108" so maybe I just lucked out?? Scott I will make my cabin 3/8" wider so I can gap it but not cut my plywood edge. This way I keep the better water proofing from the factory. On my one sheet I have to cut in haft I will put the cuts under the sole plate. My floor is 12X24 in my cabin. Mark

[Redoverfarm]

Mark I think "advantex" is the culpert of the undersized.  I am not sure with T&G "plywood" as I was more concerned with the extended time of exposure to the elements than I was about the demensions which were adjusted accordingly.

[MountainDon]

Today I found the AdvanTech® (note spelling) WEBSITE.

One interesting thing I found is their statement...
AdvanTech flooring panels are available in T and G. On T and G panels, net face width = 47-1/2"

That's all fine and dandy IF you've read their website. It might be nice if they printed a warning on the sheets. But I guess this could also be taken as a cautionary note to measure EVERYTHING before you use it.

Another yet more distressing fact I discovered is that the "find a retailer" on their website does not come up with any New Mexico dealers. I'll have to make some phone calls. Or maybe there's another source in the west.  They have one plant in Broken Bow, OK and the rest are way east.

[Redoverfarm]

Don sorry to hear that the product is not readily available to you.  There is another product that is available that has the same intended use as Advantex. The surface is smooth similar to hardboard.  They guarantee it as well but there may be a down side to their product that I asked about.  That is that their product is waterproofed around the outside by 2-3" (T&G edges). The complete top surface is waterproof.  What I was getting at is I asked the supplier if I had to cut a half sheet was there any waterproofing through the center and she couldn't(or wouldn't) answer that.  I have a friend that is a contractor and has used the other product and really likes it.  States it has alot better surface after exposure than advantex.  Never commented on half sheet cuts though.  I will try to find the company name for you to look at.

All in all if you are going to be delayed or slow getting it under roof it is well worth the money.  In this neck of the woods I believe I paid $21 sheet. 

[Redoverfarm]

Don that other product from my estimates is called "Sure Floor".  I started a search on Goggle for it but I got called for supper. I don't miss supper.  The first site is from the DIY board which discusses it some and the second is Page 1 of the Google site. 

John

http://boards.diynetwork.com/eve/forums/a/tpc/f/9221916776/m/9681069813


http://www.google.com/search?hl=en&q=surefloor&btnG=Google+Search

[MountainDon]

Thanks. It's time for me to go cook. I'll check up on this later. 

[NM_Shooter]

Don we have Advantech here in ABQ.  I called on Thursday to see what the price was (~$22.50 a sheet) but I don't remember who it was....I'm guessing it was Hunter.

-f-

[MountainDon]

Oh Good, Frank!! ...and thanks.

Thank goodness for the (few) independents that are left.    Price is not too bad either when compared to HD's or Lowe's plywood T&G at about 23.50 a sheet.

Do you recall the thickness they carry?

[NM_Shooter]

It was the 3/4 variety.  BTW.. their 3/4 T&G OSB was ~$16.

I'm going to start a new thread before I hijack this one any more than I already have.

-f-

[Willy]

It was the 3/4 variety.  BTW.. their 3/4 T&G OSB was ~$16.

I'm going to start a new thread before I hijack this one any more than I already have.

-f-

My full size sheets of 3/4" T&G were $11.00 a sheet but not the brand your talking about. My floor will be covered real fast so it is not a problem. Mark