Fastening to structural Insulated Panels (SIPS)

[Hobgood]

If you have ever designed anything with structural insulated panels(SIPs) you will know how little design data there is out there. I have a client wanting to attach stone veneer (+/- 15 psf)to SIPs with a metal lath. Code would have you attach the lath to the vertical studs @ 6" o.c. with 11 gage nails or 16 gage staple. The problem is SIPs have no vertical studs except at joint splines. The core is foam. The SIPS exterior skin is 7/16" O.S.B. sheathing. I am trying to quantify a shear/withdrawal value for #6 screws into the sheathing. (NDS) The National Design Specification from the American Wood Council maintains a minimum thread penetration depth(p)of 10d (d = screw diameter)for their tabulated screw values. The tabulated values can then be adjusted for lesser penetration by a factor of p/10d when 6d < p < 10d. The diameter of a #6 screw is .138". That being the case I would need at least .828" of thread penetration to qualify for the adjustment. How should I determine a value when the thread penetration is only .4375" (3.17d). Is there some other design data to determine design values of screws in 7/16" sheathing.