Blocking vs. Sheathing clips (H Clips) for wall sheathing

[North Sask]

I do not recall seeing the wall sheathing installed other than horizontally (running bond) for buildings I have come across in Saskatchewan. For those of us planning to install sheathing horizontally (my wall plus rim board height is greater than 10 ft, so vertical 'over-sized' sheathing is not ideal), would it be possible to substitute the blocking with sheathing clips, similar to roof construction? I believe there is a code requirement to nail all edges of wall sheathing but I am wondering if there is an exception if H clips are used.  If a person was not required to comply with the building code, would it pass the sniff test to use panel clips rather than blocking? I suppose the greater lateral loading on walls requires blocking and extra nailing. Maybe the blocking could be eliminated if the wall sheathing thickness was increased and H clips were used???

I guess the answer would vary depending on wind and seismic conditions. I am in a (very) low seismic and low wind area. The following map shows mean wind speed at 30 m above ground. Dark blue is low (3 m/s) and dark red is high (10 m/s). I would be in the dark blue band that slices across central and northern Saskatchewan.

[rick91351]

OSB is directional for shear as denoted by the arrows on the sheeting.  No building  inspector we have ever had up here paid any attention to the sheeting direction.  The one we have now called attention that we had run ours wrong.  It was not a failure or anything like that.  My framer friend got in the middle of it and what sheer was and arrow direction.  The inspector changed the subject very quickly.  Myself I like solid blocking and is required here.  H clips are required on the roof sheeting.   

[North Sask]

Rick, I don't recall which direction you ran your sheathing (and I'm too lazy to cruise your thread  ). Vertical or horizontal?

[MountainDon]

The IRC simply states that all edges of wall sheathing must be nailed. That's it.

I have some illustrations for tests with some different styles of wall bracing.  Tests to see how many pounds of force it took along the wall plane to cause deformation.  It's here someplace.     IIRC when all edges were nailed it did not make any difference to the strength, or maybe just a minor difference, if panels were vertical or horizontal. Conversations I have had with a structural engineer confirmed that there should be little difference as long as all edges were nailed.

Maybe a combination of vertical and horizontal could be used?

I believe h-clips on a roof are mainly a simple quick way to space the panels.

[rick91351]

We went with the arrows horizontal. 



One of the reasons I like solid blocking is it uses up your trim ends and board ends.  There is virtually no lumber wasted in today's building.  Where as you if I remember correctly you were wanting to pre-cut and sort of pre-assemble what you can.  And with the barging and floating involved, solid blocking might be an issue.  In fact the lumber yard brought up a pile of cull 2x4s and 6s to use for blocking - bracing and farm - ranch use and cost us nothing if I remember correctly.  And I look around and most of it is gone. 

The IRC simply states that all edges of wall sheathing must be nailed. That's it.

I have some illustrations for tests with some different styles of wall bracing.  Tests to see how many pounds of force it took along the wall plane to cause deformation.  It's here someplace.     IIRC when all edges were nailed it did not make any difference to the strength, or maybe just a minor difference, if panels were vertical or horizontal. Conversations I have had with a structural engineer confirmed that there should be little difference as long as all edges were nailed.

Maybe a combination of vertical and horizontal could be used?

I believe h-clips on a roof are mainly a simple quick way to space the panels.

I thought h - clips were required per code....   

Seems we hashed over a thread on sheer direction and arrows a few years ago?  I have been going that way ever since.....  Now I have freedom go both ways?   



     

[MountainDon]

Sheathing is stamped with its rated span between supports. Like 24/16 = 24" span on roofing with long dimension across rafters, 16" span for sub-flooring with long dimension across joists.

IRC Table R503.2.1.1(1) lists panel thickness, allowable loads, and maximum span for the different span rating stamps. Maximum span is given with and without edge support.  Footnote (d) is for "with edge support"  d. Lumber blocking, panel edge clips (one midway between each support, except two equally spaced between supports when span is 48 inches), tongue-and-groove panel edges, or other approved type of edge support. 


I could be wrong but I thought the directional arrows only applied to roofs and floors (across the rafter/joist).   So to avoid blocking the edges they are usually installed vertical.


Locally I have seen 4x12 sheets of OSB in some tall walls going up in a nearby project. Not sure what the thickness was.

[Don_P]

Sheathing is considerably stronger in the out of plane direction when the strength axis lies across the bearings. When you stand on a floor or roof you are bending the ply out of plane and your big ol foot is applying something on the order of a 200 lb concentrated load in between the supports, so you have to run those sheets across the joists or rafters. A wall doesn't typically see such concentrated loads.

The load the sheathing on a wall is trying to resist is predominantly in plane shear. Blocking and nailing all edges is the best way to get high shear resistance. If you block and nail all edges the in plane shear strength of the wall is similar either way you orient the sheets. However if you lay the sheets down you'll have twice as much blocking to do, so we usually stand them up. Ultimately, Rick's is a better wall but it does take twice the blocking.

Very rarely are H clips code required on a roof... but always use them. I wouldn't use them in place of blocking on a wall.

[North Sask]

I wasn't considering in-plane shear as the primary load on the sheathing. In my mind, wind loading was the main concern.     Now that we have that sorted out, it would seem like a pretty bad idea to substitute nails and blocking with a few clips.

My best case would be to find 4x12 sheathing but that might be a pricey special order. I'll have to check with local suppliers. Maybe I will go with a combination of vertical and horizontal sheathing to minimize my blocking requirements. If planned properly, the blocking could double as fire blocking.

[MountainDon]

Wind loading on one wall creates shear load on the walls perpendicular to it.

[Davegmc]

Just to be clear here. Do the major codes require the clips if you don't block the seams on wall sheething? Does it matter USB vs plywood? Do the codes ever required the clips on roof sheething (USB or plywood)?  Thanks!

[MountainDon]

Just to be clear here. Do the major codes require the clips if you don't block the seams on wall sheething?

The IRC simply states that all edges of wall sheathing must be nailed.

... Generally in the IRC it states that edges must be nailed every 6 inches and in the field of the panel every 12 inches; nail sizes are listed too. There are exceptions and the footnotes cover them. Nowhere are H-clips mentioned as an alternative when we are looking at wall construction.  If H-clips have been seen in wall sheathing it is not only not code, it is bad construction practice.

Maybe it will help clarify why the edges are to be nailed if we think about what happens when the winds cause a force to be applied down the plane of the wall. If the bottom of the wall is securely fastened to the floor/foundation the top of the wall will want to move in the direction the wind is blowing. If the all the edges of all the panels are not securely fastened to the supporting framing the edges will distort, lift, form waves along the edges. If the edges are all nailed as specified they are held tight to the framing.  Try and experiment with chopsticks or straws for framing. Glue or pin paper to top and bottom plates but leave some edges un-nailed.  Hold the bottom plate (straw/chopstick) in place and slide the top plate sideways. Then glue/pin the edges......


FWIW... On the Simpson Strongtie website they only talk about the use of their H-clips for use with roof sheathing.

Depending on spacing of rafters or trusses clips may be required on roof sheathing. The reference is in TABLE R503.2.1.1(1) ALLOWABLE SPANS AND LOADS FOR WOOD STRUCTURAL PANELS FOR ROOF AND SUBFLOOR SHEATHING AND COMBINATION SUBFLOOR UNDERLAYMENTa, b, c     read footnotes as well as the table or text

[archimedes]

Funny,  I've never noticed any thread where the edges of the OSB were blocked.  I'm sure it's been done,  but I guess I've just never noticed.

How would you block the edges?  With a 2 x 4 placed,  with the 1 1/2" side facing down,  between the studs,  providing a 3 1/2" nailing surface? 

[MountainDon]

Most projects have not had any panel edges that needed blocking as there were no panel edges that did not fall over the wall framing. Most have had the panel edges fall over a vertical stud or over a horizontal top or bottom plate. No need for blocking when that occurs. I can think of at least one project that the owner-builder demanded be deleted after the problem of non blocked edges between panels was pointed out. There may have been others I do not recall. And I can not think of any projects I can point to that do illustrate the need and the presence of edge blocking. 

Yes, a 2x4 laid flat between studs would be fine.

[Don_P]

Having never used those nice 9 and 10' sheets, we end up blocking everything. You can do most of it with a nailgun but a palm nailer is very handy in those hard to reach places.

[MountainDon]

nice 9 and 10' sheets

...  those are very nice