Field Gluing 1/4 plywood together? Curved? Bad Idea? 1

[seattlemike]

Hello fellow Structural Engineers,

I have a house project in which the contractor missed building a major shear wall (1/2" plywood x 12" long x 3 stories high.)

So, one idea we have is to sheath the curved (in plan) wall that is the curved stair outside wall. It is the only full height (bsmt-roof) wall. The radius of the curve is 10 ft, and the wall is approximately, 12 ft of that length.
Our shear wall previously required 10.5 ft.

So, we previous had 1/2" plywood (both sides).
The contractor wants to use (2) layers of 1/4" plywood on each side of the curved wall, because it will easily bend to fit the curve.
I actually thought they'd be able to bend wet 1/2" plywood into that shape.

So questions:
1. Can 1/2" plywood get soaked with water, bent to curve, and not lose much strength after it dries?

2. If we glue the (2) 1/4" sheets together in the field with wood glue, will that be adequate? The (2) 1/4" sheets will also be nailed 10d@3" o.c. at the edges and 10d@12" o.c. field for shear nailing. The glue merely prevents the 1/4" sheets from buckling. And plywood is normally glued layers anyway.

I think the strength will be enough. I am concerned the glue would actually make the wall too stiff, and thus negate our R = 6.5 for earthquake analysis.

Please let me know if you have any REAL experience with this?

If you are merely guessing or speculating, please say so.
I need to know what's factual and what's not.

Thanks all! I appreciate your input!

SeattleMike!

 

[woodengineer]

Mike,

I do tip my hat to you seismic designers.

I would contact APA directly (Talk to Karen Beebe). I am hesitant to use field applied adhesives as they are difficult to QC. In addition, you are soaking the plywood; I would be concerned with the glue joint interface upon drying.

Another good contact is Dr. Taylor at AF&PA.

woodengineer

 

[seattlemike]

Seismic engineering is fun. Come join us!

Thanks for the tips, woodengineer, you rock.
I had considered the APA & AF&PA, but it REALLY helps to know who to call.

Thank you,
Mike

 

[structuralaggie]

I have had REAL experience in something similar.

For one, I built a hammock stand with treated 1x4's and soaked them to help bend them. I used screws to attach them together. It worked fine, but when they dried out large gaps between the laminations. Maybe glue would have worked better, but you would still have significant swelling occur perpendicular to grain when they are wet, and significant shrinkage when they dry. I don't think plywood would be any different than solid stuff. If I were to do it again, I would use thinner material with more laminations. So I would recommend staying away from the water, especially for something that is actually structural.


Also, I always have framers building stair stringers out of 1/4" plywood that is both nailed and glued together. They usually end up being 3" or so thick by the time they are done, and actually turn out pretty stout. I always have a disclaimer on my drawings that says the stairs are designed by others, but if I had to I would design a stringer like this.

So in speculation, I don't see why gluing two sheets of 1/4" plywood together would be any different than using a single 1/2" sheet.