horizontal or vertical plywood sheathing.

35334 Views 6 Replies 5 Participants Last post by Thurman, Jul 12, 2009

Clutchcargo

Discussion Starter · Jul 11, 2009 (Edited)

Is a wall built with plywood sheathing stronger with horizontal or vertical sheathing orientation?
I've searched on the web but it sounds like horizontal is stronger but a lot of builders build walls the the ply vertical.

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Carpenter

· #2 · Jul 11, 2009

Sheathing

Every house that I've ever built has it's sheathing installed horizontally. The reason for this is purely for strength - horizontal plywood (or drywall or whatever 4x8 material you're using) will increase a wall's strength by spanning several more studs than if installed vertically. Also, plywood is always at it's strongest when it's grains run at a right-angle from the framing member. Don't forget that all your exterior plywood should be half-lapped for additional strength.
Hope this helped.

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PaliBob

· #3 · Jul 12, 2009 (Edited)

Clutchcargo said:
..... but a lot of builders build walls the the ply vertical.

I would have thought horizontal, but I did a search that leads me to think that both methods are acceptable so long as blocking is added so that all the panel edges are nailed:

Ref from the Californa bay area retrofit bulletin board:
http://bayarearetrofit.com/forum/view_topic.php?id=88&forum_id=3

For the 16'x6' wall in question their call is for vertical

A more general question to the JLC Q/A on Horizontal vs Vertical Sheathing
answers with a declaration that Horizontal Sheathing is stronger "in many instances"
http://www.jlconline.com/cgi-bin/jl...82?c=75f0ad7ad6b9aa6fb4c2d7485905f387&p=1&q=1
.

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Gary in WA

· #4 · Jul 12, 2009

They are about the same if the horizontal application is left unblocked. But blocked, it is about 40% stronger. On a wall, it is allowed either way if the panel is thick enough for the stud spacing. For floor and roof diaphragms, the spanning of multiple members comes into play as the face grain of ply and fastener length and spacing, but not in walls, unless it is an engineered shear wall.

Most local jurisdictions require ply on the corners and every 25' of wall, as per UBC. This is to transmit the wind and seismic loads to the foundation. They require blocking at all panel edges. IRC 602.10.7

When I started building in '73, we cut let-ins at corners and 25', installed 1x4's, nailed after square, installed black board or foil face, then raised it. Installed cedar horz. siding after windows and felt. We did T-1-11 siding, 4x8, vertically. So it was no wonder that when ply started being used as sheathing for shear , we installed it vertically as well. Especially in production framing, we did not spend time putting in extra blocking as required to pass inspection, with horz. appl. Only once have I installed ply horizontally, I think it may be a local "how you learned" thing. Be safe, G

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Carpenter

· #5 · Jul 12, 2009

Sheathing

That's interesting, Gbar: I'd honestly never heard of vertical sheathing on an outside wall before. I suppose with blocking it would be just as strong, as you say. As per the let-in bracing, I find that cutting in a 1x4 45 degrees from the bottom plate is integral.
What we're starting to see more and more of around here are outside walls being built out of 2x4 (first floor !), on 16" centers, sheathed with 1 1/2" styrofoam and metal let-ins (12' long, looks like a T - just snap a line and run the saw about 3/4" deep)
On the second floor, the spacing changes to 19.2"(save a stud for every 8'). It doesin't make for a very solid house. To date, I've only seen one building company employ this method, but they're a big one.
The next generation is really going to say that they don't build them like they used too - and for good reason!

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Gary in WA

· #6 · Jul 12, 2009

Yes, we went through that saw-curf slot for the Simpson angle metal brace for about 5 years, in the '80's. It was an L, not the new and improved T, they sell now. Lol. We used 88-5/8" studs with plates and ply came down onto rim 2-3/4", for positive tie. Studs were always 16"o.c., no blocking, all edges on stud or plates. About that same time, we switched to 92-5/8" studs, 97-1/4"OA, ply 3/4'down from top flush, and up 3/4" + - from bottom flush, and no required blocking. Then in '00's, switched to 102's and 9' osb, that covered wall complete, so no blocks, which was a little stonger as more nailing room. I think the industry up here is just lazy and doesn't want to put in blocks! Lol.

We did/do the floor joists on 19.2" with 3/4" Gold edge osb, talk about spongy!! And for a while they touted the Advanced Framing concept- windows and doors put in on layout, using a Simpson bracket instead of a trimmer. http://www.strongtie.com/products/connectors/hh.asp Made it hard for the finish carpenter!

Then there is the other extreme, first and second floor walls- seismic everything, everywhere. Not just your earthquake straps (sometimes 25), but also 24" coil strap every 15' (tie stories together) and special horizontal MST37's at the windows- sill and header- both sides, for wall shear flow. Carried over the next two studs from the window with blocking.

Then the three man crew, rambler in 7 days, two story in 11. Layout all the plates at the lumber pile........... I get tired just thinking about it. Lol. Be safe, G

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Thurman

· #7 · Jul 12, 2009

GBAR, it appears you are in Washington State, and Carpenter, I don't know where you are located but I enjoyed that information as I used to work for a home builder when I was much younger and things sure have changed her in S. Ga. Recently I was in Walton County, Florida with my bro-in-law who is a developer in the Atlanta area, and we went to look at some homes under construction there. Walton Co. now requires any home or condo with at least two floors of livable space to have "Hurricane tie-downs" that are no less than one-inch (1") threaded rod that goes entirely through the flooring (be it concrete or wooden) and all the way up through the exterior walls to the top plate of the top floor. We viewed some three story, small footprint, homes that had these rods every ten feet (10') all the way from the concrete pad through the uppermost toplate. These were twenty-foot (20') galvanized rods connected with a threaded rod connector and locknuts on both sides. I also notice that all exterior sheathing was no less than 1/2" plywood, roof decking was 3/4" plywood, and there were none of these units being built with any OSB anywhere.
I can't imagine what this adds to the cost of these units. Maybe with the hurricane damage they have had down there in the last three years this is practical. Thanks, David

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