Toggle bolts ratings in EFIS

[madcowscarnival]

There is a municipality nearby that requires certified calculations for sign installation in facades. I've been askedto review and provide calculations and certification for facade mounted signs. The signs I've looked at thus far have come out to about 41lbs per bolt in shear, and slightly more than that in pullout (no FS applied). The bolts are 3/8" toggle style through EFIS with 3/8" plywood backing. Common sense tells me the bolts mounted in that facade will be fine, however, I would like to prove it in calculations. I can find mfg. tables for pullout and shear ratings in gypsum board, but nothing in plywood. How would I go about calculating those values? Thanks

 

[a2mfk]

I would not want to depend on 3/8" plywood and a toggle bolt, even with clamping forces, for anything even remotely structural. You will also have a hard time not damaging the EIFS in attempting to get good clamping force. I would only rely on attachment to the metal/wood studs. If this is the type of facade on a retail building and there is attic access, perhaps blocking can be added at the sign locations to facilitate installation.

Also be sure to specify some type of sealing when dealing with penetrations of EIFS. Bad news if moisture gets behind it.

 

[XR250]

The shear will have to be supported by the foam unless you can somehow cantilever the fastener - good luck. Can the foam take 41 lbs of shear from a 3/8"Ø cylinder?

 

[madcowscarnival]

The installer is going to try to access the back of the facade to determine the underlying structure and/or gather additional information on EFIS section. Maybe I can get a fastener attached from the inside.

 

[ztengguy]

wouldnt the clamping force be enough not to cause the anchors to have to be considered cantilevered?

 

[CELinOttawa]

Ztengguy - Agreed, but quite Franky I would not be confident in the permanence of this solution.

I suppose it is pretty doubtful that the sign would be applied to any covering directly in contact with the EFIS, and so this argument is likely moot due to clamping not occurring through an air gap.

 

[ztengguy]

I guess I would need to see the sign and its geometry. 41lbs shear per anchor doesn't strike me as very much.

 

[madcowscarnival]

I will post the results when the contractor gets to the site and gains access to the interior. The 41lbs has some built in FS; 20psf LL was applied to the plan area of sign and raceway. The lettering is extruded aluminum attached to an aluminum raceway; sign weight was assumed at 200 lbs, though will likely come in at 150lbs with wiring and lighting installed.