Skip Sheathing Diaphragm Strength

[BecomingCurmudgeon]

A closed post talked about calculating the diaphragm strength of the skip sheathing underneath a cedar shingle roof. One of the commenters mentioned that the AITC Timber Handbook had an example calculation of this. My version of the Handbook, the 5th, does not have any examples.

Does anyone know which version of the Handbook was the example I'm looking for?

Thanks.

 

[msquared48]

I have versions 1 through 4, but could see no mention of skip sheathing, only horizontal sheathing at the roof, and diagonal sheathing at the floors and shearwalls. A reference was made to the Western Woods Use Book in version #4, but I found nothing there either.

I tried to model this ovewr 20 years ago, using a two nail force couple as the resisting factor at the intersection of each skip sheathing member to each rafter, but did not have much success. Good luck.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[BecomingCurmudgeon]

I did some further digging and I came up with a source and example problem.

Look in ATC 7 _ Guidelines for the design of horizontal wood diaphragms, Appendix A.3 for the calc to find the diaphragm strength.

It will be low.