LSL Wall Studs Bowing

[H57]

I was asked about some LSL wall studs that are bowing and I can't figure out the cause so I wanted to see if anyone else could provide some insight.

House is 42'x32'. Roof trusses (vaulted) span across the 32' dimension with gable ends. Bearing walls on each side are 15' tall. End walls (non load bearing) are 18' tall studs maximum. There is a full length porch along one 42' side. There is an open second floor (loft) opposite the entry/porch (17'x42'). The entry faces west.

The north non-load bearing wall has a 1" bow in it (strong axis). At the northwest corner the wall is straight. At the ~midpoint of the north wall it is straight as this is the start of the second floor (loft). Between the corner and the second floor the wall stud bow gets worse. About 8' from the corner is the maximum wall bow (~1" from a string line pulled top plate to sill). The top plate and the bottom plate are both straight. Wall framing is 2x6 lsl studs @ 16" o.c.

The west load bearing wall is straight. The south non-load bearing wall is straight. The east load bearing wall is straight.

Any thoughts on the cause?

Thanks.

JH

 

[JAE]

A couple of questions - are the studs bowing max. at mid-height or is there some kind of lean (out of plumb) to the studs?

Is the bowing inward or outward?

The only think I can think of is that possibly those particular studs were exposed to moisture/wetting and have warped as they dried.
Usually these products are fairly dimensionally stable so an initial camber/bow wouldn't be expected without some external cause.

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[H57]

The studs are bowing max. at mid-height. The top plate is directly above the bottom plate so there is no lean to the wall.

The bowing is outward and was not there when initially installed.

My understanding is that the house was erected last winter and siding/roofing was put on immediately after. Insulation was delayed and installed in the spring/early summer. I don't think that the house has been climate controlled during the last year. They are doing interior work this winter and now they've noticed the bow in the wall. No idea when it bowed, but it wasn't that way during initial erection or installation of the siding/roofing.

 

[RHTPE]

How is the roof framed and how does it connect to the North wall over the portion that is bowed outward? Does the roof overhang the North wall gable end?

Is it possible that deflection of the roof trusses is throwing a moment into the top of the taller portion of the North wall studs?


Ralph
Structures Consulting
Northeast USA

 

[H57]

The north wall is non-load bearing. There is a gable end truss directly above the wall. There is a small roof overhang. Outriggers are attached to the first truss south of the wall and cantilever over the gable end truss.

 

[mike20793]

Can you post any pictures?

 

[msquared48]

Temperature / moisture differential causing warping.

Mike McCann, PE, SE (WA)

 

[Ron]

Are the double top plates separating? What kind of wall sheathing? I doubt there's enough dead load to buckle the studs, so I'm inclined to agree with Mike. Pictures or sketch would be helpful

 

[hokie66]

Agree with Mike. Although manufactured wood products are more dimensionally stable than sawn wood, they are still affected by differential moisture changes. 18' is a tall wall, loaded or not, so wood was probably not the best material choice.

 

[Triangled]

wondering if siding related

 

[CBSE]

Are the LSL studs full height? Or is there a plate break without any lateral support, such as diagonal bracing? This would create a knee joint and cause some amified deflection due to wind loads. Maybe I'm misunderstanding the framing though?

 

[H57]

The LSL studs are full height.

Siding is LP smart side lap siding.

At this point I'm inclined to think that it may be moisture related.

Thanks.

 

[jayrod12]

hokie66,

18' gable end wall out of wood is becoming all to common. Have you seen any of the houses being built nowadays?

18' tall is really no big deal up here north of the 49, at least in the residential market. Always non-load bearing (gable end or side wall), always a significant wood wall (or at least it should be). With LVL studs this is easy to accomplish. It's also typically just crammed full of windows, so then you end up having to do a bunch of crazy stuff like we've seen Medeek doing.

 

[msquared48]

Another thought with the 18 foot high gable end wall studs...

This effectively eliminates the vertical shrinkage across the eliminated double top plate that the rest of the house sees. This could add to the bowing effect seen.

Mike McCann, PE, SE (WA)

 

[RHTPE]

Assuming that the gable end truss sits on top of the bowed portion of the end wall, what provisions exist to maintain the gable end truss in the same plane as the gable end wall? Has this truss rotated slightly (outward at the bottom chord), perhaps due to whatever lateral truss bracing has been installed?

Ralph
Structures Consulting
Northeast USA

 

[XR250]

I did a 29' gable end wall out cont. 2x10's Worked nicely and no bowing.