So I Was Popping A Straight Line Today....

wallmaxx

Typically, when I run sub floor, I come in the width of the plywood plus an eighth from the rimboard that I have chosen to start from, and pop a reference line (parallel to that rimboard). Pretty common, huh. Then I glue, and lay down sheets so that they line up with the sub flooring tongue edge along that line to start the first row straight.

WELL....I thought I knew how to pop a straight line....!?

As I was running the first row, I noticed that along the 4' edge I was tight at the line but a hair loose at the rimboard. It wasn't making sense....no wind....double checked my measurements....checked my string line for straightness...nothing.

The only thing left was to look at the plywood itself.

Holy cow batman. When I looked down the tongue edge of a sheet, it had a 1/4" crown towards the groove edge. The sheets are mildly skewed.

It is regular 5/8 plywood T&G.

Has anyone else run into bad subflooring from the factory?

neolitic

Yes indeed!
Long ago I gave up on trusting "factory edge",
and of course square went out the window
while Nixon was still around.
A couple of years back I discovered that
the new quality standards have even reached
the fine folks who make cabinet grade veneer plywood.
¾" walnut veneer had no straight "long" edge,
not square corner to corner, and even had beveled edges.
"Trust no one grasshopper!"

(BTW have long held ¼" for deck line.)

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KentWhitten

I miss my 48" net faces from WA state.

I love when you hit one of those splinters you can't see sticking straight up and your line hits it and you are laying sheets and "WTF????"

I got into the habit of chalking every row. Tells you where to stop gluing and how far to hit it in. You don't need some laborer saying "little more left.....now right.....now back left..."

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Custom Cabinetry - Portland, Cape Elizabeth, Scarborough, Kennebunkport, Yarmouth, Falmouth, Cumberland, Ogunquit, Maine

Salmon Falls Cabinetry

A W Smith

We have always run the groove edge along the snap line. not the tongue edge. Two reasons, Easier to follow the line as the groove edge it right on the joist members and not above it. Also easier to drive stubborn sheets together with a mallet and block of wood without damaging the edge. And yes I have noticed some sheets not square for quite a few years now.

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Double-A

Too true, I get enough of that at home.

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KentWhitten

I mentioned this in a thread awhile back. Two guys were working for me in Maine. They come up and said, without any humor.."why do you put the groove side out instead of the tongue? Everyone puts the tongue out"

He was dead, dead serious.

Although!!! I have a tip, though I haven't used it myself. Occasionally we get a builder who likes to use 5/8 T&G on the roof. As always I put the groove side uphill. Builder comes along and says same as above. I respond back like I always do. He dropped one on me and I thought it was a decent idea. If you put the tongue up on the roof, when it rains on the roof before it gets closed in, then it won't rain so much in your building. Even could be a small leak diverter if you have a tiny leak. Though I would want to know if I had a leak.

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If you correct your mind, the rest of your life will fall into place ~Lao Tzu

Custom Cabinetry - Portland, Cape Elizabeth, Scarborough, Kennebunkport, Yarmouth, Falmouth, Cumberland, Ogunquit, Maine

Salmon Falls Cabinetry

DrewD

We use strictly 3/4" Advantech and I have to say I haven't seen too many sheets that were very off much more than an 1/8" at the most. I work with an older guy who has about 30+ yrs who likes to blame everything on the lumber. Joist layout is a little off....the subfloor isn't 8 ft, they cut it short. This walls a little out of plumb....the studs are junk Canadian wood. It goes on and on like that. I've learned to tune him out. I was tought to run the groove in as well. I showed up at the site and two guys were laying the floor, claimed the sheets were messed up from the lumber yard. I watched them lay the tongue in and beat the hell out of it with a piece of PT and sledge. Ruined more than half of the tongues so the sheets wouldn't go together tight. Last floor they did.

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"Listen, you're my family and I love you but you're all terrible at what you do here and I feel like I should tell you, I'd fire all of you if I could."

Jason Whipple

Same here, we use nothing but Advantech for sub floors and roofs. To many problems with plywood. The one you (OP) mentioned and the delamination factor when it gets wet. I find Advantech goes together a little faster too. That helps a bit in regards to the cost difference.

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Historic House Restoration, Cincinnati, Ohio
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bcframer

i've come across sheets that aren't truly square. i don't know who would put the grove side out for a starting line that would make t&g awkward.. a good block and a sluggo on the grove side makes life easy but to each his own

ownerbuilder

That would be like pounding your pud. I have never heard of anyone laying sheets with the groove out. I would only use 5/8 plywood if i knew the sub-structure was going to get under layment. I've never had a problem with 3/4 t&g ACX or better for standard substrate.

neolitic

Easy to find ¾" T&G-ACX out there is it?
What species?

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