Floor sheathing parallel to joists?
dukeofwsu
| Posted in Construction Techniques on
Okay, its not in the IRC, I looked, but I’ve always run my subfloor perpendicular to the joists.
I’ve got a layout to do monday however that’d cut a lot cleaner by running my T&G along the same axis as my floor joists.
There seems to be no code reference to direction with structural panels, nor does it say anything in the framer’s handbook (either Weyerhauser’s or LP’s). Having always gone against the grain, I’m looking for advise saying this is a good or bad idea.
FYI, the house will have mostly hardwoods on this floor, but other areas will be tile over floated backerboard, and the floor is designed L/480.
Replies
All plywood and osb I've used has had a span direction indicated on it, although a lot of builders sheath their roofs the same way whether they strap them or not. Also, wouldn't you have to do a lot of blocking?
"I've always run my subfloors perpendicular to the joists..."
Sounds like you're a smart man....keep it that way.
Plus, always stagger your seams. Running plywood with the joists will weaken your floor, and regardless of the IRC, this practice goes against most general building codes and practices...so don't even think about it.
Davo
Edited 1/28/2007 2:25 am ET by Davo 304
I'm sorry to say that I don't have the most current IRC handbook handy, but on page 86 of IRC (YR 2000) handbook for single & 2 family dwellings, there is in the bottom right hand corner of that page, Table R5603.1 which is titled Minimum Floor Thickness of Sheathing Lumber.
The table depicts what thickness of sheathing is appropriate, based on 3 categories:
1) Joist/beam spacing ......24 inch, 16 inch, 48 inch, etc.
2) Indicates sheathing to be run perpendicular to said joists.
3) Indicates sheathing to be run on a diagonal to said joists.
Notice that this table does not include sheathing being run parrallel to said joists...reason being...this method is not approved.
So, based on these findings,.... plus, wait a minute, also..... Table R503.2.1.1(2) subparagraph a) ; located on page 88 of same handbook, which states the following...."Plywood continuous over 2 or more spans and face grain perpendicular to supports."...
I would say that IRC does in fact stipulate that plywood floor sheathing should not be installed with the panels running parrallel to the joists.
So there you have it. It IS against (IRC) code to install floor sheathing in a parrallel fashion.
Hope this solves your dilemma. Bite the bullet and do it the right way...not the easy way.
Remember, if it was always easy, then there would be no need for carpenters.
Davo
T&G runs perpendicular for a reason, being the 'T'" fits in the "G" over the air space between the joist with the majority of the plays of ply wood running perpendicular to the joist. OSB strands you may have noticed run the same way too. And the more joist the ply runs perpendicular the less bounce to the floor. And the building will stay square under stress, especially the higher floors under sever wind loads. And it is not allowed.
I hope that is enough "and's" for you to produce a better product verses saving $25.
Best to you and yours, Chris.
Some say I know too much.
Bad idea.
The ply will tend to sag, buckle and roll if run parallel. Additionally, if you are using t&g, you'll have to adjust your layout to something like 15.689" oc.
blue
"...if you just do what you think is best testing those limits... it's pretty easy to find exactly where the line is...."
From the best of TauntonU.
I was goiing to post that as well, you only get 47-1/2" of face on those T&G sheets, which makes landing on a joist difficult.
The subfloor I get here has 48" of face.
Really? I haven't seen that here. It measures 47-1/2" from the edge of the groove to the edge of the tongue. Or 48" total.
That would suck. For instance I did a floor that's 24 feet wide recently. That's exactly 6 sheets if they're 48", but 7 if they're missing that half inch. It was 32 feet long so we would have needed four extra sheets just for some 2" rips, or I suppose we could have blocked the edge, a PITA either way. You might ask your lumberyard if they can order full face instead of scant face, if you get in a situation where it matters.
It happens all the time, you almost have to layout your sheets so you don't end up with a 2" piece. I didn't know that was available, I will check on it thanks.
I also have the option of scant face or full face in T&G sheathing from my local yard.
If it makes you feel any better, I've yet to come across the full-face variety as well. Reputable sources say it exists so a framer can still dream, can't he? :)View Image
Now I don't feel so bad. It would be nice to get full size sheets. A big time saver for sure.
For a while there I thought I was living in the twilight zone.
Maybe ours is full face because we live in rain country and it is really just swollen.. ;-)
I wish mine would swell that way! If it swells it goes from 3/4" to an inch. Time for the belt sander! :)
Sorry, long time no computer. The layout worked w/o a bunch of blocking because we had several intermediate beams to land on due to wall removal.I went ahead and ran perpendicular anyway, why risk it.Also, FYI, around here my face for 3/4 T&G sanded & plugged is 48x96 and has no axis stamped, however, if you want to get OSB or old-skool 1&1/8, you find that you're out by the tounge width, and the osb shows an axial strength arrow.-dukeDCG Your Neighbor's Contractor LLC
"A wrongdoer is often a man who has left something undone, not always one who has done something."--Marcus Aurelius
Ply wood doesn't need an axis strength arrow! Anybody who needs to be told why should not be doing this sort of job.
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A little hijack here, but what about the second layer, I'm getting ready to put 1/2" osb down over the 3/4 t/g osb sturdifloor.Would parallel to the joists make any deifference there?I was thinking the strength axis being perpendicular might be a good thing in this application?
It is always better to have teh strength axis perp to th ejoists. In your case, you already have the structural, and the layer you are placing is only underlayment technicly. You'll be gluing and nailing at 6-8" oC too, right?
So axis is less important, but I wouldn't lose sleep if a small piece in a cormer were turned wrong...except that you mention OSB, which doesn't fill me with confidence.
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Well actually screwing and gluing, what's your preference on hitting the joists with fastners on this layer, I've seen and heard both to avoid them, and to hit them with 3" screws also.As a side note, all I can find for the dura-spin here locally is "piffen" screws in 1-1/4, I'm still searching for some gold ones. No tile, only carpet, and vinyl for the bath and mud rooms.I can easily go perp to the joists, I was really wondering if parallel might be better on the second ply.I am aware that you and others dislike osb as compared to plywood.
You get picked on a lot as a kid or something?
In addition to the plywood/OSB being manufactured to span in only one direction in most instances (for subflooring anyway) and your layout issues, you will also have to block all of your non T&G seams as subflooring should be supported on all edges. That's why T&G subflooring is T&G..... it's self supporting along the long seam.
Most sheathing and dcking i've seen lately even has a stamp on it every so often for the consideration of the unknowing that states with arrows on a directional line "Strength axis"
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Taunton University of Knowledge FHB Campus at Breaktime.
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I have seen what you are suggesting done in a home with a lot of trouble. The T&G joint will move in such a way that people can feel and often hear it when they walk around the joint area. A lot flexing happens at the joint when run parallel with the joists. Plus the fact that most plywood is to be run perpendicular to the joists for its maximum strength.