Wall Sheathing - do I need blocking?

[DigitalFusion]

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?

 

[FunfDreisig]

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]

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]

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]

[/QUOTE]

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

 

[IDASHO]

Guy with the gun isnt playing it too safe either.

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


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

 

[1500hd]

Agree with IDASHO should use 9 footers. This will help with "shear" no joint in between sill and top plate.

 

[DigitalFusion]

I have 4x8 sheets as I got a stellar deal on them.

 

[IDASHO]

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.

 

[DigitalFusion]

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]

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]

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.

 

[DigitalFusion]

I did end up finding out the code. Blocking is required on horizontal seams in the sheathing.

 

[Shocker]

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]

Why would you get 4x9's if you are running horizontal?


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

 

[IDASHO]

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.

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

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

 

[IDASHO]

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]

Why would you get 4x9's if you are running horizontal?

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]

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...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]

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]

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]

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...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]

Maybe you should read the link I provided. ...

I did. But I also think for myself

Funf Dreisig

 

[IDASHO]

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

Site talks about plywood. OSB would be no different.

 

[FunfDreisig]

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]

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]

...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]

Children, children please.....lets all have a 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........

 

[kbs2244]

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]

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

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
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]

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.

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]

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]

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]

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

 

[IHI]

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

 

[BooUrns!]

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

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 ***** 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]

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

 

[IHI]

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

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.

 

[IDASHO]

Nah, all roofs here are done in 5/8 osb 7/16 is too thin even for subs

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

 

[IHI]

Nah, all roofs here are done in 5/8 osb 7/16 is too thin even for subs

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 "I can side my house with plastic 4 times for the price of the cement stuff" everything here is low buy in 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