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sheathing gaps for expansion

RJT's picture

If I leave an 1/8" gap for expansion, I'd have to cut that much off each 4x8 otherwise before a couple of joists I'm off center. How ya do that?

 

(post #93377, reply #1 of 22)

I belive right on the sheet it says "sized for spacing."


1/8" gap is 1/16" per sheet side.


Unless it's T&G ply getting the sheets to 0 gap is almost impossible.


No need to cut.


 


Who ever invented work didn't know how to fish....

"Some days it's just not worth chewing through the restraints"

(post #93377, reply #5 of 22)

FYI,


I framed and sheathed an addition on my house 10 years ago. I used the OSB board and did not space it at all. I didn't know at the time I was supposed to!! I wrapped it in Tyvex and it made it through the winter before I got around to siding it the next summer. It gets very humid here in NJ but never noticed any expansion at all.


 

(post #93377, reply #2 of 22)

Hey, RJ,


Sheathing is not plywood.


Plywood does not have words and symbols printed on one face.


Sheathing does not come in A, B, C, or D face grades.


Plywood comes in whole inch sizes, usually 48" x96".


Sheathing comes in fractional inch sizes, usually 47 15/16" x 95 15/16".


Sheathing can be OSB.


Hope this helps,


SamT



I now believe all inspiration comes from God, it is meant to be shared, and it demands total commitment to succeed. When that happens, Providence acts too.
John Hatch


SamT
A Pragmatic Classical Liberal, aka Libertarian.

I'm always right!
Except when I'm not.

(post #93377, reply #4 of 22)

Okay, thanks, blame it on the tape, it wasn't telling me right, or else I need glasses. It's working out right.

 

(post #93377, reply #13 of 22)

samt .. my first inclination would be to say that all sheathing is plywood..


 there is no such thing as the American Sheathing Association


 there is an APA though..


i think you are working with a speciality product.. dimensioned for long runs..


 normal plywood  ( sheathing OR FLOORING) does in fact have printing all over it..


 with span ratings for flooring .  or roof decking..


 


 i agree with you .. spacing is not only required, it's good practice.. and can prevent future buckling.. which will telegraph thru the roof shingles..


 but i really do think all of the normal plywood we get at the lumber yards is not dimensioned to a lesser number to allow for spacing.. everything we get is 48 x 96


and the terms sheathing and plywood are interchangeable.. sheathing is a use of plywood... as is decking ( flooring )..


 but , hey, whadda i no ?


Mike Smith   Rhode Island : Design / Build / Repair / Restore

Mike Smith   Rhode Island : Design / Build / Repair / Restore

(post #93377, reply #14 of 22)

but , hey, whadda i no ?


Me neither


SamT



"You will do me the justice to remember that I have always strenuously supported the right of every man to his opinion, however different that opinion may be to mine. He who denies to another this right, makes a slave of himself to his present opinion, because he precludes himself the right of changing it."   Thomas Paine


SamT
A Pragmatic Classical Liberal, aka Libertarian.

I'm always right!
Except when I'm not.

(post #93377, reply #15 of 22)

Heck, all I know is that when I bot "mill certified" in PW 35 YO for my own house, the 1/2 was actually 7/16th..and 1/32 shy of 48" .  Joists were spaced right on 16.  3" Ring shank nails worked fine for 33 years, no squeaks, the EQ couple years back produced about 1 squeak per 1000sq ft.   New thread direction - go screw and glue!!

(post #93377, reply #16 of 22)

The original question was over 7/16 osb on a 14x28 addition to the barn, with less than a 4/12 slope, I'm using roll roofing. The siding was 3/8" textured plywood without grooves and no spacing but now it is buckling badly. Instead of ripping it off I'm thinking of running a saw down the seam and on the 24" center as all will be covered with battens. Why did this junk buckle? It did it in between nails even, and it is primed on both sides.

 

(post #93377, reply #17 of 22)

RJT


I assume that your barn has animals or hay in it.


These put out lots of warm water vapor, which has penetrated the wood and expanded it.


Go ahead and kerf it, then wait till it dries out and the bulges shrink (they may never go completely away) then paint.


I'm sorry no one told you about this issue before you built.


Mike Smith, go to the APA Plywood Publications site and download publication X505-R, it will explain the difference between plywood and sheathing and tell you what those numbers on sheathing mean.


SamT



"You will do me the justice to remember that I have always strenuously supported the right of every man to his opinion, however different that opinion may be to mine. He who denies to another this right, makes a slave of himself to his present opinion, because he precludes himself the right of changing it."   Thomas Paine


SamT
A Pragmatic Classical Liberal, aka Libertarian.

I'm always right!
Except when I'm not.

(post #93377, reply #18 of 22)

sam, thanks... good site... no definition of "plywood" though..


 and the grade stamps are the same ones we get that you get...


i think my confusion arises because i commonly use a 2 word descriptor .....as in     


 " plywood sheathing"  as opposed to say " board sheathing"...


Mike Smith   Rhode Island : Design / Build / Repair / Restore

Mike Smith   Rhode Island : Design / Build / Repair / Restore

(post #93377, reply #19 of 22)

When ever I get ready to do a roof or floor, I always measure the plywood and space accordingly (or don't space if it is exactly 4x8).

You get out of life what you put into it......minus taxes.

Marv

(post #93377, reply #20 of 22)

Well, technically, the word 'plywood' covers all flat and pressure formed wood based material mad from thin layers of woo0d glued together with each layers grain running perpendicular to the next.


Commonly speaking 'plywood' is that stuff that is 48"x96" (usually, could be 108", 120", or, 144") and is not face marked, and is used by cabinet makers 'cuz it is supposed to be a finish surface. But I have heard "OSB plywood" and once heard  "Particle board plywood" in one of the big boxes.


When I want to buy 48x96 'plywood' I say that I want ACX or BCX, etc. When I want sheathing I will specify 24/16 sheathing or similar.


Kinda like 'soda'. Do you want Coke, Nehi grape, or lemonlime. If you want "Soda", you have to say "soda water". Go figure.


SamT



"You will do me the justice to remember that I have always strenuously supported the right of every man to his opinion, however different that opinion may be to mine. He who denies to another this right, makes a slave of himself to his present opinion, because he precludes himself the right of changing it."   Thomas Paine


SamT
A Pragmatic Classical Liberal, aka Libertarian.

I'm always right!
Except when I'm not.

(post #93377, reply #21 of 22)

sam.. when i want something i spec it ..


 1/2" CDX Fir , 5-ply... 


or  3/4" AC P&TS,


or 3/4" CDX, T& G, P&TS..


they all have grade stamps.. except the A side .. or MDO... or specialty plys.... those are the only times  no grade stamps...


 i never order plywood, but , it is all plywood..


 unless it's not.. like Advantech..


 


Mike Smith Rhode Island : Design / Build / Repair / Restore

Mike Smith Rhode Island : Design / Build / Repair / Restore

              www.mfsmithbuilder.com

(post #93377, reply #3 of 22)

I build in the Pacific NW and to be honest with you, we almost never consciously gap our OSB.  I'm talking about sheets that have not been cut in any way  The painted edges seem to prevent swelling. 


Now I have noticed swelling when you leave the stack of sheathing uncovered, but I have not noticed any swelling when the sheets are installed.  That isn't to say that it won't happen and it's best to follow the manufacturers directions.


By the way, we have used OSB subfloor since it was introduced, and we have never had to sand our floors.  We have never had the problems that others have with OSB and moisture.


Personally, I try not to install the pieces tight, but sometimes it ends up that way.  I haven't had to relief cut anything. 

www.pioneerbuildersonline.com From Lot 30 Muirkirk

http://picasaweb.google.com/TimothyUhler                                     

(post #93377, reply #6 of 22)

I've never spaced my cdx and never had a problem in over 27 years.


Be spaced (out)


                    andy


 


Emptiness is not really empty, emptiness is full of everything.


The "everything",  just isn't manifest




http://CLIFFORDRENOVATIONS.COM

(post #93377, reply #7 of 22)

I did a commercial job with 150+ linear feet  of flooring and the sheathers kept having to sister nailers to my joists until they complained to the foreman that my layout was off. I educated them about spacing sheathing cuz' my joists were right.


Use an 8d to space, drive home the nail after the next piece is in.


SamT



I now believe all inspiration comes from God, it is meant to be shared, and it demands total commitment to succeed. When that happens, Providence acts too.
John Hatch


Edited 9/6/2003 12:24:34 PM ET by SamT


SamT
A Pragmatic Classical Liberal, aka Libertarian.

I'm always right!
Except when I'm not.

(post #93377, reply #8 of 22)

Sam


      I could be wrong (it does happen : ) but I've never spaced my sheathing and haven't EVER had a problem.


If you accounted for an 8d nail, by the time you got three four sheets down the line.....well.....you should have told the sheathers you did that cause I don't really think its a standard practice.


Be well


         andy



  You can "be" the universe, but you can't know it. You are the answer- but you can't know you know.




http://CLIFFORDRENOVATIONS.COM


Edited 9/6/2003 1:10:45 PM ET by Andy Clifford(Andybuildz)

(post #93377, reply #9 of 22)

What is not standard practice? Setting joists to 16"OC? Or not spacing sheathing?


SamT



I now believe all inspiration comes from God, it is meant to be shared, and it demands total commitment to succeed. When that happens, Providence acts too.
John Hatch


SamT
A Pragmatic Classical Liberal, aka Libertarian.

I'm always right!
Except when I'm not.

(post #93377, reply #10 of 22)

spacing sheathing

  You can "be" the universe, but you can't know it. You are the answer- but you can't know you know.




http://CLIFFORDRENOVATIONS.COM

(post #93377, reply #11 of 22)

Well then, if you work behind me on a long run of joists or studs, your non spaced sheathing is going to start missing wood, cuz I layout exactly on 12", 16", 19.2",  or, 24" centers. Unless you have figured out how to have 47 15/16"(whatever it is, 29/32?) reach 48".


Of course, on most houses it won't show up as the runs just aren't long enough. 4 sheets ran horizontal on a wall is only 1/2" short in 32' and there is probably a door in there to break the run.


Those guys following me on that commercial job happened to be laying the sheathing parallel to the joists and there was aprox 150' to lay those 4' wide pieces down on


SamT



"You will do me the justice to remember that I have always strenuously supported the right of every man to his opinion, however different that opinion may be to mine. He who denies to another this right, makes a slave of himself to his present opinion, because he precludes himself the right of changing it."   Thomas Paine


Edited 9/6/2003 9:17:15 PM ET by SamT


SamT
A Pragmatic Classical Liberal, aka Libertarian.

I'm always right!
Except when I'm not.

(post #93377, reply #12 of 22)

Good point.....I suppose over all the years something must have been in the  runs to break it up cause I've never run into a problem even on roofs.


Probably the longest roof run to be sheathed was about 50'.


a


  You can "be" the universe, but you can't know it. You are the answer- but you can't know you know.




http://CLIFFORDRENOVATIONS.COM

(post #93377, reply #22 of 22)

My understanding is that the gap left between sheathing sheets is to allow for shrinkage of framing members, rather than expansion of relatively stable plywood.