Replies

1. 
   hammer1 | Feb 22, 2008 03:09pm | #1

   7/16" OSB on 24" centers, for roof sheathing?!! How low can you go? We use 5/8" CDX plywood.

   Beat it to fit / Paint it to match

1. 
   Sphere | Feb 22, 2008 04:15pm | #2

   Thats why they make "H" clips. For 24" centers. Spheramid Enterprises Architectural Woodworks

   "Success is not spontaneous combustion, you have to set yourself on Fire"

2. 
   artworks | Feb 22, 2008 04:17pm | #3

   That is common for  a roof here in  Manitoba, most use 'H' clips between rafters. The OSB should have a span rating  printed on the sheet. I seen some 3/8 used with the clips, and it is rated as such for 24" o/c, but I wouldn't use it. Yes 5/8 is better, the $ makes it prohibited here.My choice is 1/2" FIR plywood on 16" oc, or next best 24" oc with 'H' clips.  ( Plywood is a little slippery however )

   'IF IT WAS EASY, EVERYONE COULD DO IT!"

3. 
   5brown1 | Feb 22, 2008 05:31pm | #4

   They do make a full 1/2" OSB and it is amazing how much stronger it is.
   With the clips you get a sturdy roof.

1. 
   frammer52 | Feb 22, 2008 05:43pm | #5

   The 1/2 inch osb doesn't telegraoh where the trusses are either.  the downside is it is quite a bit heaveyer than 716

1. 
   Sphere | Feb 22, 2008 05:48pm | #6

   Quite a bit heavier?

   Lets see..a 1/16 " x 32 sqft =2"x12"x12", or =1'x4'x1/2"..whassat about 5 lbs?

   I don't think I'd notice the difference from 7/16 to 1/12. but from 7/16 to 3/4 I would.

    

   edit: OK add a little..3/8th OSB is 1.26 lbs sqft (G)

   Spheramid Enterprises Architectural Woodworks

   "Success is not spontaneous combustion, you have to set yourself on Fire"

   Edited 2/22/2008 10:00 am ET by Sphere

1. 
   Piffin | Feb 22, 2008 06:14pm | #7

   I have been using Advantec 1/2,5/8, and 3/4" for so long that I am spoiled. But on a cheap shed last yeara, we got some 7/16osb and I was amazed how much lighter it was and how much weaker it was, doing the floppy tuna when we handled it.The better quality brands like the Huber Advantec use better resins and more pressure in manufacturing so it IS indeed heavier as wel as stronger and more water resistant.That last is probably part of the reason why people see sheathing sag at 24"oc too. OSB regular used as roof sheathing can sometimes be absorbing moisture in poorly vented attics and getting weaker with age. 

    

   Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

1. 
   joeh | Feb 22, 2008 06:19pm | #8

   So, once again it all comes down to

   "To Vent, or not to Vent".....

   Joe H

2. 
   popawheelie | Feb 22, 2008 06:23pm | #9

   Venti... Venti...

3. 
   cargin | Feb 22, 2008 10:10pm | #14

   Piffin

   OSB regular used as roof sheathing can sometimes be absorbing moisture in poorly vented attics and getting weaker with age.

   I can testifiy to that. We did two modular (trailers) homes last year. Tear off and reshingle. Both had a plastic/brown paper underlayment over 7/16 OSB.

   I think the underlay didn't let the roof breathe. We had weakness and damage between the joists and at the seams. So 4' up the roof and every 2' we had this discoloration and a weak spot.

   Not to mention the water damage at the valleys.

   It was amazing how much stiffer the new OSB was compared to the older and vapor damaged OSB.

   Rich

2. 
   frammer52 | Feb 22, 2008 06:31pm | #10

   when you are pushing 150-300 sheets onto a foor it adds up quickly.

   trust me. been there done it!

1. 
   Sphere | Feb 22, 2008 06:33pm | #11

   I was just bustin your pebbles..I know, I have handled enough to feel the pain.Spheramid Enterprises Architectural Woodworks

   "Success is not spontaneous combustion, you have to set yourself on Fire"

4. 
   Jim_Allen | Feb 22, 2008 07:25pm | #12

   BAck in MI, the builders shipped 7/16 for the walls and 1/2" for the roof. It's amazing how much difference the 1/16 makes.

   Here in Texas, if we ask for 1/2" to be shipped, they ship 7/16" and they don't even bother telling you that they don't have 1/2"!!!!

   It's been a learning process!

   You have to do what you have to do, given your regions limitations on materials. If you don't want the sag, you have to spend the money on the 5/8" or special order something else or put the support members closer.

   Bob's next test date: 12/10/07

5. 
   CapnMac | Feb 22, 2008 08:56pm | #13

   Is all 7/16 OSB equal?

   Nope.  It does not help that some 7/16 is actually 11mm (or 10mm)--around 13/32"

   Leaving the H clips out is not helping at all. either.

   But, it will all work out, in 15-20 years, when that third layer of shingles sags into the attic one day . . .

   Occupational hazard of my occupation not being around (sorry Bubba)