View Full Version : Wall Sheathing - do I need blocking?


DigitialFusion
03-22-2009, 12:31 PM
Hey all,

I have 9' sidewalls, and 4x8 sheets of OSB I plan to attach vertically. I have been told two completely conflicting code requirements by two different professionals.

I was told by one union carpenter that I will have to put horizontal blocks between the wall studs where there is a seam in the OSB. Something like this image I found on the intarweb. (see below) I was told by another contractor that I do not have to do this, code doesnt require it. I cannot seem to find any information on what the exact code requirement is, and being sunday, I cannot call in to ask. Anyone know the final word on this?

http://benitoloyola.com/build2/Wall%20blocking.JPG

FunfDreisig
03-22-2009, 07:38 PM
I don't know about "code" but....

OSB is a much better shear panel when it is installed HORIZONTALLY and offset by 1/2 sheet on each course. And it is a good idea to block walls to make them stiffer AND to retard fire running up the stud bay. BTW The blocking you show is often called "fire blocking" and is usually installed at the level shown.

FWIW I blocked my walls at 4ft (and 8ft where the wall was over 10ft). I promise you a 14ft high wall gets a lot more solid with blocking at 4 and 8ft even before the OSB shear panel goes on.

Funf Dreisig

ddawg16
03-22-2009, 07:46 PM
You need the blocks.

The OSB is your shear wall....it is what gives the garage is lateral strength...
The blocks attach the ends of the OSB so that the ends are attached which allows for greater strength.

Additionally....stager the sheets....that is, one goes high, the other low....its the same idea behind how you lay brick....

This is the kind of thing that seperates the good contractors from the bad.....while I may not be an exact friend of unions....I do have high respect for well trained union guys....

65Stang
03-22-2009, 08:02 PM
You need the blocks.

The OSB is your shear wall....it is what gives the garage is lateral strength...
The blocks attach the ends of the OSB so that the ends are attached which allows for greater strength.

Additionally....stager the sheets....that is, one goes high, the other low....its the same idea behind how you lay brick....

This is the kind of thing that seperates the good contractors from the bad.....while I may not be an exact friend of unions....I do have high respect for well trained union guys....

x2. Even if you do not have to block per code, all edges of the panels need to be nailed, otherwise, you could push on the edge and it would separate from the adjacent edge. Water intrusion would be eminent.

65Stang
03-22-2009, 08:03 PM
http://benitoloyola.com/build2/Wall%20blocking.JPG[/QUOTE]

Man, whomever is taking the photo is a brave soul with that nailgun setting at an angle like that.... :headscrat

IDASHO
03-22-2009, 08:07 PM
Guy with the gun isnt playing it too safe either.

No ear plugs or eye protection? Come on guys, common sense :headscrat


That said, if you have 9' walls, why not use 4x9 sheets of OSB? :confused:

1500hd
03-22-2009, 08:43 PM
Agree with IDASHO should use 9 footers. This will help with "shear" no joint in between sill and top plate.

DigitialFusion
03-23-2009, 11:42 AM
I have 4x8 sheets as I got a stellar deal on them.

IDASHO
03-23-2009, 09:22 PM
I wouldnt touch them, unless they are free.

The additional cost of a 4x9 sheet is more than worth it, when you consider the additional time and materials required to install blocking, hang a 4x8, and hang a 1' strip across the top.

More cuts, more lumber, more nails, more labor.:headscrat

DigitialFusion
03-23-2009, 09:25 PM
to some people perhaps... however I am enjoying the building experience and taking my time. To me, its worth saving several hundred bucks to have to rip a couple sheets into 11" strips, and put some blocking in, which only strengthens the structure.

FunfDreisig
03-23-2009, 09:52 PM
to some people perhaps... however I am enjoying the building experience and taking my time. To me, its worth saving several hundred bucks to have to rip a couple sheets into 11" strips, and put some blocking in, which only strengthens the structure.I enjoy the DIY stuff too. And I'm more than willing to put more time into making my garage stronger. But... as I posted before, despite the common application of OSB vertically (mostly to save labor for blocking), most OSB is stronger when applied horizontally than vertically*; particularly when it is staggered by 4ft. And adding blocking to a 9ft wall at 4ft and 8ft will make your walls much stiffer than adding it a only at 8ft (i.e. just 1 ft down from the header).

Funf Dreisig

*FWIW the OSB I used on my garage includes an APA stamp which clearly indicates the "strength axis" as horizontal.

IHI
03-24-2009, 08:09 AM
We're not "required" to use fire blocking here, and the only place i ever see it used is when soffits are built in and fire blocking is then needed as a fire stop in case fire does get into a stud cavity.

Do yourself a favor, call city hall, talk to the building department and let them tell you if you HAVE to use it. If no, then you decide if you want to use it or not. It does increase overall wall strength, so it's not a bad thing other than lost time and added material expense, but the building will be just fine without it. We've built a number of 10-12' sidewalls without it and once sheathing was installed it stiffen them up regardless. there are nailing schedules on everything so just make sure your getting enough nails installed per code.

As for water intrusion, i gotta ask...WHAT????? once the building wrap is installed, and everything is correctly flashed, there is no way for water to get in.

DigitialFusion
03-24-2009, 08:36 AM
I did end up finding out the code. Blocking is required on horizontal seams in the sheathing.

Shocker
03-24-2009, 10:15 PM
So, where are you guys finding 4x9 sheets of OSB? I have never seen it.

Mine are 10 ft walls. I wonder what the cost difference is.

skeletonizer
03-24-2009, 10:53 PM
Why would you get 4x9's if you are running horizontal? :headscrat


It is a garage. Most codes don't require an inside wall sheathing at all much less blocking said sheathing.

IDASHO
03-24-2009, 11:03 PM
OSb can be installed both vertical and horizontal. The shear value is the same.

So, where are you guys finding 4x9 sheets of OSB? I have never seen it.

Mine are 10 ft walls. I wonder what the cost difference is.

They make 4x10 as well :)

Most large retail building supply outfits stock 4x8, 4x9, and 4x10 sheets of OSB. And if they do not stock it, they sure as heck can special order it.:thumbup:

The stuff we stock at my work right now is priced out close to this:

4x8= $7
4x9= $12
4x10=$15

IDASHO
03-24-2009, 11:05 PM
Blocking is required on horizontal seams in the sheathing.

Which is why most builders run OSB vertical. Fewer cuts, less lumber, fewer nails, less labor, less $$$$

FunfDreisig
03-24-2009, 11:10 PM
Why would you get 4x9's if you are running horizontal? :headscrat

It is a garage. Most codes don't require an inside wall sheathing at all much less blocking said sheathing.I think the OP was running the OSB vertical on 9' exterior walls. So 4x9 sheathing is much quicker and easier but less strong than 4x8 sheathing applied horizontally.

FWIW interior walls CAN be structural even if they are not load bearing. For example, they can provide significant shear support for an exterior wall when that wall has large door openings, etc.

Funf Dreisig

IDASHO
03-24-2009, 11:21 PM
I think the OP was running the OSB vertical on 9' exterior walls. So 4x9 sheathing is much quicker and easier but less strong than 4x8 sheathing applied horizontally.

Care to explain this statement? Are you referring to sheer values?

Assuming the installation follows the nailing schedule, the sheer value is the same, whether the OSB is installed horizontal or Vertical.

Here is the APA site for reference..

http://www.apawood.org/pablog/index.cfm/2006/8/1/Help-Desk-Question-Should-Wall-Sheathing-be-Installed-Horizontal-or-Vertical

Key point...

The racking resistance of APA plywood or OSB wall bracing panels and the lateral load capacity of a shear wall for wind and seismic loading are not affected by the orientation of the sheathing panels. Panels may be installed with the long, or strength, axis either horizontal or vertical

and...

Although not required by model building codes, some local jurisdictions require blocking of horizontal panel joints at wall bracing segments (generally building corners and at 25 foot intervals in long walls). For this reason many designers and builders prefer to install sheathing with the long axis vertical, thus avoiding the need for additional blocking.

FunfDreisig
03-24-2009, 11:26 PM
OSb can be installed both vertical and horizontal. The shear value is the same....Then why does the APA stamp on my OSB clearly indicate the "strength axis" as horizontal?

FWIW I understand that vertical application of OSB is "common". And some manufactures clearly show their OSB applied both ways. BUT that does not mean that the strength is IDENTICAL. It simply means that the shear strength is acceptable in either application. It is obvious that vertical application of ANY sheathing (without stagger) produces a weaker structure. Vertically applied sheathing produses a COMMON edge along ONE stud every 3rd stud. OTOH horizontal sheathing with a 4ft stagger distributes these vertical edges and nailing across more studs AND requires (due to code) blocking that provides both increased stiffness and a fire block.

Funf Dreisig

IDASHO
03-24-2009, 11:31 PM
Maybe you should read the link I provided. ;)

The strength axis of some APA OSB panels is, however, in the short or across panel direction. Marking on the panels such as, “Strength Axis, This Direction,” with arrows pointing in the suggested direction, identifies the strength axis of the panels. There is no standard for the mark, so it can vary from manufacturer to manufacturer.

I have spoken to many engineered building material reps about this so-called strength axis mark.

It is simply an overlooked carry-over from plywood. It really has nothing to do with OSB.

FunfDreisig
03-24-2009, 11:39 PM
Care to explain this statement? Are you referring to sheer values?

Assuming the installation follows the nailing schedule, the sheer value is the same, whether the OSB is installed horizontal or Vertical.

Here is the APA site for reference..

http://www.apawood.org/pablog/index.cfm/2006/8/1/Help-Desk-Question-Should-Wall-Sheathing-be-Installed-Horizontal-or-Vertical...My point (see my post above) is that the sheathing can be applied both ways. BUT since applying sheathing horizontally requires (due to code) additional blocking, the resulting walls do NOT have the same shear strength. Nor do they have the same fire block protection.

Why don't you continue building your walls with the OSB vertical and I'll continue building my walls with the OSB horizontal and with additional blocking :)

Funf Dreisig

FunfDreisig
03-24-2009, 11:41 PM
Maybe you should read the link I provided. ;)...I did. But I also think for myself ;)

Funf Dreisig

IDASHO
03-24-2009, 11:44 PM
Do you still think horizontal provides a stronger shear?

Ive got a website for ya. Just found it actually....

CLICK ME TO CURE ALL YOUR PROBLEMS (http://mgacon0.tripod.com/plywood.htm) :)

Site talks about plywood. OSB would be no different.

FunfDreisig
03-24-2009, 11:55 PM
Do you still think horizontal provides a stronger shear?
...Forget the orientation of the sheathing. What you are basically arguing is that BLOCKING a wall at 4ft and 8 ft adds ZERO strength to the wall. Let me repeat, NO, NONE, NADA, ZILTCH additional strength what-so-ever, even when the sheathing is attached to both the vertical studs and the horizontal blocking.

Funf Dreisig

IDASHO
03-25-2009, 12:05 AM
Hardly. You are the one that is torn up about the blocking.

I could care less. And I do.

I never use it, so long as I can find structural sheathing panels tall enough to span the height of the wall, and still have the framing pass inspection.

Let me ask you again...

Did you read read the site I linked to?

Here, let me quote it for you, to save you the trouble...

The weak spot in the horizontally sheathed wall is the continuous plywood joint at 4-foot height where the panel edges are least supported. ....... If you add horizontal 2-by blocking and nail the plywood at the horizontal plywood joints, the wall with horizontal panels would have the same shear strength as the wall with panels installed vertically.

Gee, what did I say a while back? here, Ill quote myself...

OSb can be installed both vertical and horizontal. The shear value is the same.

FunfDreisig
03-25-2009, 12:34 AM
...I never use it, so long as I can find structural sheathing panels tall enough to span the height of the wall, and still have the framing pass inspection.

Let me ask you again...

Did you read read the site I linked to?...As I have posted previously, I have read ALL of your links prior to my replies. And have read many others on the subject prior to this evening.

And I think I have found the principle reason for our 'discussion'. I have never designed/built a structure so simple that I could find a sheathing panel "tall enough to span the height of the wall" except in very limited sections. IOW in the structures I have designed/built, the majority of the walls are taller than typically available structural sheathing and contain a significant number of large window/door openings that break up the span between sole plate to top plate. Hence my preference for horizontal applications with blocking.

Ciao - Funf Dreisig

ddawg16
03-25-2009, 06:38 AM
Children, children please.....lets all have a :beer: and keep it civil.....

I've seen it both ways....but I know code in my area requires the blocking....

Now....if a 4'x10' costs $15 which is over twice the cost of a 4'x8'....blocking sounds pretty cheap.

One other aspect to cosider.....depending on the code....most of them require blocking if the length of stud is 8' or more......in my garage, my wall studs were about 7' (stem wall made up the difference) but I still put blocking in some locations to keep the studs straight....some tried to bow a little bit.

So.....at the end of the day, for all this discussion....the blocking could have been installed and all the OSB hung........

:beer::beer::beer::beer::beer:

kbs2244
03-25-2009, 11:21 AM
Besides the fire protection the real advantage of the blocking at the seam is the reinforcing it gives the edge of the panel from being pushed in.
If you put the panels vertical then the seam will be high enough to make any pushing against it a small worry.
If you go with a panel that goes floor plate to top plate then the plates give that reinforcment.
I still like to put in blocking at 4 to 5 feet above the floor to give me a solid place to anchor the electrical to.

IDASHO
03-25-2009, 09:28 PM
Now....if a 4'x10' costs $15 which is over twice the cost of a 4'x8'....blocking sounds pretty cheap.

Twice as much sure, but in the construction business, time is money. And so it materials.

Let me explain my position this way... Ill warn you though, this will get a bit in depth :spit:

Lets take a simple ranch style home, single level, 9' walls.

Lets say the house is 24x48

Thats 144' of running wall, and 1296 square feet of wall. For the sake of simplicity, lets omit all doors and windows, and assume all framing is 16" OC

Lets also keep in mind that the nailing schedule is 6" around the perimeter of the sheet, and 12" in the field. I will add labor for extra cuts and requiring nailing, but omit labor for the actual installation of the sheathing.

So, 144' of wall, thats 36 sheets of 4x9 OSB. $540
No blocking required.
A 4x9 sheet requires 52 nails around the perimeter, and 16 nails in the field. 68 nails per sheet. Thats just less than 2500 sheathing nails. One case of 8d Galvanized ring shank sheathing nails $65

Thats $605 in materials, no additional labor added.


Now lets take your 4x8 sheets, plus blocking.

You would need 41 sheets of 4x8 $287
Blocking needed. 108 14.5" long blocks. Thats 108 cuts. Labor? Add 2 hrs @ $20/hr $40
Thats an additional 135' of lumber, or 17 more 8' 2x4's or 2x6's Add $80
Thats also an additional 432 16d framing nails. Add $35
Labor for all that blocking? Add 2 hrs @ 20/hr $40
Now lets figure in your sheathing nails.
This is a bit trickier, as you have many sheets ripped down to 12" strips. 5 sheets, actually. Labor? Add .5 hrs @ $20/hr $10 18 strips.
Those 18 strips require 20 nails per sheet. 360 nails total for the 12" strips
A 4x8 sheet requires 48 nails around the perimeter, and running horizontal, you need 15 nails in the field. Thats 63 nails total per sheet. 2268 nails for 36 4x8 sheets plus 360 nails for the strips, thats 2628 8d sheathing nails total. Thats more than a case. Add 2 cases, $130

So, thats $532 just in materials, and an additional $90 in labor (I went easy on labor)

$622 total.

You loose money with the 4x8, and you spent a lot more time installing it :drool:
If anyone wishes to question my numbers, feel free. I went through them quick, I might have made a mistake somewhere. Doubt it though!

IHI
03-25-2009, 10:07 PM
IDASHO- i get it, you get it, but many home owners dont get it, but thanks to your post above maybe it'll shed some light.:thumbup:

Old CDX is directional, the grain goes one way. OSB is multi/uni directional, there is no set way and that is why horizontal/vertical it does'nt matter, the strength is the same regardless. i have found the vendors get their OSB from different manufacturers, some have both horizontal and vertical lines marked, other's horizontal only. I like going vertical whenever possible (so long as sheets are marked, i'm not about to tie 1 or two guys up marking and chaulking lines 16" just to run them vertical, that'd cost too much, but i like tieing to and bottom plate together. It helps cut down on truss lift as an added benefit as well.

FWIW, last year our city changed ruling on narrow walls, for years we could build walls as narrow as 2' with no issues, now we cant build anything narrower than 2'6" UNLESS we install structural sheeting (OSB) to both sides of the wall to help prevent racking over time. When we are forced to do this, since it's deemed "structural" it now falls under a nailing schedule which is crazy IMO since you blasting so much steel into the sheets there's not much wood left to hold it together LOL!!

skeletonizer
03-25-2009, 10:24 PM
OSB is multi/uni directional, there is no set way and that is why horizontal/vertical it does'nt matter, the strength is the same regardless.


4'x8' 7/16" OSB has a strength axis, it is marked right in the grade stamp. Standard wall sheathing is oriented on the long axis.

IDASHO
03-25-2009, 10:27 PM
FWIW, last year our city changed ruling on narrow walls, for years we could build walls as narrow as 2' with no issues, now we cant build anything narrower than 2'6" UNLESS we install structural sheeting (OSB) to both sides of the wall to help prevent racking over time. When we are forced to do this, since it's deemed "structural" it now falls under a nailing schedule which is crazy IMO since you blasting so much steel into the sheets there's not much wood left to hold it together LOL!!

OSB does seem to go to MUSH when the nailing schedule gets real tight.

Ive found that it is also very dependent upon the manufacturer of the OSB.

All APA rated, Exposure-1, some stuff holds nails VERY well, while others seem to mush.

I have found that Weyerhaeuser OSB is by far the most stable. VERY dense. SO dense that cuts barely splinter. Whereas other OSB not only splinters when cut, it flakes and peels from the cut.

Another note that very few are aware of as far as OSB goes, is that every cut joint must be painted to maintain the warranty of the sheathing. That is something that even I dont bother doing. And I NEVER see it done on job-sites.

IDASHO
03-25-2009, 10:28 PM
4'x8' 7/16" OSB has a strength axis, it is marked right in the grade stamp. Standard wall sheathing is oriented on the long axis.

See post #21 :thumbup:

IHI
03-25-2009, 10:35 PM
4'x8' 7/16" OSB has a strength axis, it is marked right in the grade stamp. Standard wall sheathing is oriented on the long axis.

I have'nt seen a sheet of 7/16" since the first and only job we used it on year and years ago, so thanks for the info:thumbup:

BooUrns!
03-26-2009, 01:19 AM
I have'nt seen a sheet of 7/16" since the first and only job we used it on year and years ago, so thanks for the info:thumbup:

It went out of fashion up here years ago aswell. It was once used as roof sheathing but I think builders got sick of having to differentiate between it and 3/8th wall sheathing. I imagine roofers didn't miss it much either although talking to some of them, they'd still bitch if it was 3/4" roofing ply.

As to the labour difference between sheathing 4x8 or 4x9, it gets down to nominal availability. Around here, 4x8 is the only thing you use. Anything can be special ordered but why go to all the trouble? Does it make sense to pay twice as much for four more square feet and go ot the trouble of the special order?

We also differ from your standard building practice in that it is typical to attach osb horisontally/staggered and stapled down with 1/2" crown staples at around 6" o.c. There are a few guys out there who use 2" nails still but it's not really cost effective and it's much slower. A Bostitch 650s4 or 750s4 crown stapler can put a sheet down tight in seconds.

Platform framing is the typical method here with osb applied before the walls are stood. Sometimes I would stand attached garage sidewalls unsheathed but never the front. It's quite common to have height changes in a wall so ripping sheets is just part of the job.



Blocking is required by my national code in 2x6 walls over 12'.

IDASHO
03-26-2009, 06:25 PM
7/16 is the standard here, as well as across most of the US

As for nails vs staples, many people here use staples, and they have proven to have a better holding abilitiy, and resist pull-thru much better.

But I fail to see how a staple gun is any faster at installing a sheet of OSB than a nail gun :headscrat

IHI
03-26-2009, 06:39 PM
7/16 is the standard here, as well as across most of the US

As for nails vs staples, many people here use staples, and they have proven to have a better holding abilitiy, and resist pull-thru much better.

But I fail to see how a staple gun is any faster at installing a sheet of OSB than a nail gun :headscrat

Yeah, if your the framing sub and just erecting whatever the GC speced out, i can see greedy folks trying to max profits using thinner substrates, so i'm lucky that I'm the guys specing and the guy building so we do 1/2" walls, and when i can talk folks into it 5/8" on the roof...i'm sure you done roofs with 5/8" too and it's unreal the stiffness you gain from only an 1/8" extra thickness!! My #1 hammer jockey is all of 280lbs...former college football player, and i cringe when we're sheathing roofs with 1/2"...everywhere he walks it looks like railroad ties when a train is going over them...it just sinks. 5/8" does'nt hardly budge a bit.:beer:

IDASHO
03-26-2009, 06:50 PM
Nah, all roofs here are done in 5/8 osb 7/16 is too thin even for subs :spit:

Hardiplank and Vinyl are king here, so the entire exterior of the houses are sheathed in 7/16 osb

IHI
03-26-2009, 07:46 PM
Nah, all roofs here are done in 5/8 osb 7/16 is too thin even for subs :spit:

Hardiplank and Vinyl are king here, so the entire exterior of the houses are sheathed in 7/16 osb

Our area is mostly ghetto salaries, so trying to upcharge for the thicker decking is all but impossible. Vinyl is king, very few people are here ever ask for cement siding...too spendy for them even though it's lifetime:headscrat "I can side my house with plastic 4 times for the price of the cement stuff" everything here is low buy in:mad: people think they're saving money buy buying cheap/low and have no clue they're going to spend twice as much since they'll be redoing it later...but somehow our country has dumbed down society to think that is okay:headscrat

BooUrns!
03-26-2009, 08:27 PM
7/16 is the standard here, as well as across most of the US

As for nails vs staples, many people here use staples, and they have proven to have a better holding abilitiy, and resist pull-thru much better.

But I fail to see how a staple gun is any faster at installing a sheet of OSB than a nail gun :headscrat

You can bounce fire a bostitch stapler in a 4' row along the osb over the stud/truss in less than 2 seconds. If you're careless and lose track of your line you just hit it again on the right location.

Nails guns need to be lined up and they just can't be fired as fast as a stapler. Air nailers also take longer to load and the cost of the nail fasteners is much much higher than the staples.

In my locale, we don't have the high wind seasonal storm or seismic issues you have in parts of the US so we can use staples for all structural sheathing applications (unless otherwise specified).

When you're doing production framing for a large builder, the lumber packages are supplied by the builder. You build it to meet code and to their order.

I'm not all that proud of the vinyl ghettos that I helped to create. When I look at the ridiculous rates that siders charge for their labour, I can see why new home builders really don't have a choice but to offer anything but vinyl and stucco. Hardie plank doesn't cost much more for materials but they increase the labour rate to offset the increased material cost.

At least they finally pushed through an amendment to the building code here to put firestop drywall under the vinyl siding. There were a few fires in new sub-divisions that stared in one home and spread quickly to dozens because the siding caught fire so quickly and spread.

IDASHO
03-26-2009, 09:35 PM
Interesting note about the staples.

I have a sheathing stapler, but have never used it. Ill have to pick up a case of staples and give it a whirl. I didnt know they were so fast.

Installing a ton of hardwood T1-11 in the past, I always have a few cases of 8D Galvanized Ringshank siding gun nails. They work fantastic on OSB. Just have to be particular about depth, shooting them with a framing nailer.

The vinyl here is quite disgusting in my opinion. I hate it. At least it is normally reserved for apartment complexes and rentals. And every vinyl order we get is a pretty sweet sale. For one 12-16 unit complex, thats $18-$20k in vinyl.

Run of the mill homes get the hardiplank.

tcianci
03-26-2009, 09:37 PM
Wow, talk about getting your panties in a knot! Everyone who has commented has brought valid points to the discussion. I would like to add my 2 cents worth... As far as the shear strength of the WALL assembly, there is probably no difference in strength afforded by the orientation of the panel. The strength axis refers to the panels' ability to resist deflection. In the case of a wall assembly, a wall sheathed with the panel running vertically would be less able to resist deflecting caused by a wayward stud and that would result in a little bulge or dip in the wall surface.

The comment about OSB being essentially non directional is not true.. The "O" stands for ORIENTED. The pieces of wood are arranged with a definite orientation that gives strength along the long dimension of the panel, the same as plywood. In our locale, we always run the panels horizontally, no blocking along the horizontal seam, the unsupported edges of the panel are the ones that lie in the strength axis. Sometmes we use PLY CLIPS to keep the panel edges from deflecting on roof sheathing.

As for the thickness of the panel 1/2 inch plywood or 7/16 OSB is the norm here. The panel thickness contributes to the overall thickness of the wall assembly so, you need to use either 1/2 or 7/16 to be compatible with the jamb depths (typically 4-9/16 inches for 2x4 walls) of the doors and windows. 5/8 plywood laid with the grain 90 degrees to the rafters or trusses makes for a very stiff roof assembly. I have seen 7/16 OSB used on roofs and within a few years you can actually see dips in the sheathing so pronounced that you can see the individual rafters through the roof job! That 1/8 or so between the hallf inch plywood or the 7/16 OSB and the 5/8 plywood on a roof makes a world of difference especially if you are hand nailing the roof shingles. On the thinner stuff, it's like trying to nail into a piece of rubber, everything bounces!

IDASHO
03-26-2009, 09:43 PM
A little late to the party tcianci, the keg is dry, chips and dip already eaten, and everyone has gone home :spit:

porschedude996TT
03-26-2009, 09:58 PM
How much shear wall is required. I only needed 4 feet from each corner, but I placed OSB on the entire outside wall. I did this because I didn't want to deal with different surface levels or shiming the outside material. Technically I only needed a 4 x whatever the wall height is, in my case 10 foot. If you plan to use the 4 x 8 on a 9 foot tall wall, then you're going to have a seam the whole length. I would stagger the joint and block behind it. How much material and how long is it really going to take, a couple of hours to nail in some 2 x 4 x 14-1/4 pieces... It will improve the wall strength.

skeletonizer
03-26-2009, 10:04 PM
...there is probably no difference in strength afforded by the orientation of the panel.

The pieces of wood are arranged with a definite orientation that gives strength along the long dimension of the panel, the same as plywood.


:headscrat.......................

suobs
01-01-2013, 11:31 AM
OSb can be installed both vertical and horizontal. The shear value is the same.

Nope on the shear value for horizontal unless blocking is used. Vertical is much stronger than unblocked horizontal. About the same with blocking See the link below which is the source of the quote below and also note it pretty much considers plywood and OSB to be equivalent:

http://mgacon0.tripod.com/plywood.htm

Structural Sheathing
Figure 2 shows the two most common ways to sheathe walls with plywood or OSB (Oriented Strand Board)*. Often, the carpenters run the plywood horizontally. For residential construction, builders often use 7/16-inch plywood nailed with 6d common nails. If the plywood is nailed according to minimum code requirements, a 20-foot wall with horizontally applied plywood has a total design shear capacity of 2,460 pounds. That means the wall can resist over a ton of force applied laterally at the top plate.

When the same plywood is installed vertically, the shear capacity goes up to 3,280 pounds. The strength of the vertically sheathed wall is greater because all the plywood panel edges are fastened to solid framing, and there are no plywood joints parallel to the shear force. The weak spot in the horizontally sheathed wall is the continuous plywood joint at 4-foot height where the panel edges are least supported. (When plywood shear walls fail under load, the failure begins at the panel edges, with the plywood pulling away from the framing and pulling out the nails, or tearing through the nail heads.) If you add horizontal 2-by blocking and nail the plywood at the horizontal plywood joints, the wall with horizontal panels would have the same shear strength as the wall with panels installed vertically.

*OSB looks like a bunch of wood chips glued together (that's what it is). OSB performs as well as plywood in most applications — if you keep it dry.

suobs
01-01-2013, 11:39 AM
I would be curious to know if shear value goes down when sheets are smaller, for example is shear of a wall made of 4x4 sheets with blocking at all intersections the same as shear of a wall made of 4x8 sheets?

grumpygator
01-01-2013, 12:36 PM
****I don't use osb.I don't care if they call it 7/16,15/32 or 31/64 it's all junk. Omni-directional my a$$. It's cr@p no matter what way you install it.
One hit from my 28 oz estwing = hole the size of the head.
4 Ply 1/2" plyWOOD or get some one else.
Had a talk with the head building inspector a few years back and asked him if osb is really strong both ways why do I have to turn it up on end when i sheet a hip? Since I have known him for over 25 years and we used to work for the same guy bending nails he just looked at me called me a trouble maker and walked away.
So to recap osb bad ,4 ply 1/2 plwood good.
As far as blocking I wold rather put it in the wall then in the trash.
******Just Saying*************Gator************

DigitialFusion
01-02-2013, 09:02 AM
this thread is over 3 years old.

5lima30
01-02-2013, 01:02 PM
Our building dept requires blocking only on the corners but I blocked my garage all the way around. BTW, I have seen a lot of 9' sidewalls around here where they used 4x8 sheets and then used a "band board" of 1x or 2x material to make up the difference.