Shear Walls - no OSB on a residential wall 2

[Flyboy76]

My builder did not use OSB on the exterior of 1 wall on my new house, they are using styrafoam/chicken wire/stucco like the other exterior walls but leaving off the OSB board underneath. His input was that the shear walls were determined by the engineers, if it wasn't a shear wall it didn't require OSB, it was drawn that way and that this was a common practice in the industry. There should be no measurable impact to heat loss, srength, etc... Does this sound right?
It was on the plans that way, and it did pass inspection, I've just never seen this done before. These guys do a nice job, they are very reputable, but I am just a little uneasy about that wall...

 

[whyun]

Although contractor may be correct in that only shear walls would "require" structural sheathing such as OSB or plywood, typically engineers would specify on the drawing that sheathing be provided entire line to avoid a let-in condition. For example, area above a door between two shear panels would be sheathed eventhough it was not needed by design.

Although structurally there may not be an impact, it may affect the aesthetics of the wall where the transition occurs.

 

[BFPartners]

That is one scary cost savings measure... So what will prevent the wind from cracking the stucco and styrofoam? Where is the strength in that wall?

 

[DaveAtkins]

I have designed some apartment buildings without OSB exterior sheathing. The interior GWB resists lateral loads.

DaveAtkins

 

[samdamon]

Flyboy-

Wood studs in a wall sheathed on one side with properly attached gyp board can be considered laterally braced. Those studs can carry gravity loads as well as if they were sheathed on one side with OSB.

If, as you say, you have engineering drawings that specify shear wall locations in other places in your project, it sounds like lateral loads have been considered in the design of the structure and your questionable wall is not part of the lateral force resisting system. Is that correct?

Heat loss I can't comment on.

Regards.

 

[AlohaBob]

Stucco makes good shearwalls. It's common practice in some areas. Where engineered, they provide the required lateral strength. No additional lateral elements are necessary beyond that. Once the lateral system is provided, you can more cost effectively meet the other desired properties for your walls.

Fiberboard is a less expensive sheathing product, but provides very little lateral strength. It provides a better R value than most materials. If this product is mixed with the sheathing for engineered shearwalls, someone is actually being wise in terms of budget and resources.

 

[damstructural]

Is there ANY OSB on this exterior wall? Even prescriptive codes often require a minimum length of OSB at the ends of exterior walls. Since this was engineered, I would assume that some portion(s) of this wall was designed as a shear wall segment. If that's not the case, and the entire wall is unsheathed, then I think you may still have a good reason to question the design. The engineer may have dragged the lateral load into a parallel wall, or maybe the loads are small enough for stucco & gypsum. I'm not used to seeing that in California. My guess is that its fine, but you should be able to find out why its okay.

 

[SperlingPE]

Is this an exterior wall?
Can stucco span horizontally across the studs to transfer out of plane wind load to the studs?
Is this wall connected to any diaphragm element (i.e. floor or roof)?
This wall will see some kind of lateral load if the answer to any of the above are 'yes'. Don't rely on city inspection/plan review. Ask the engineer if no osb was his/her intent?