Kneewall Bracing?

[Ismellelephant]

I'm building a 26x30' barn. The 2x4'studded walls are to be 8' with a 2' knee wall for more loft height. The roof pitch is 8:12. The 16" o.c. 2x10" rafters will have a birds mouth cut and attach to the top of the kneewall. I feel I need to brace the kneewall somewhere to prevent the kneewall from bowing outwards but I'm not sure how to do this. Should the kneewall be braced to the floor joists of the loft? If so, it there a certain angle the braces should be set at? Thanks for any info

[mjpliv]

You are correct that rafters transmit the loads down and outwards (called outpush). Most building authorities require that you install suitable methods of restraint for the rafter tails. The deeper the rafter material, the farther up the rafter length this restraint can be positioned.

But in your case, with only a 2' knee wall and only 8/12 roof pitch then the only choice would be to tie the knee wall back to the floor system and these restraints would have to be installed at least every 24". These connections will be under a great deal of tension so I would strongly suggest you have then designed by an engineer (not as expensive as it sounds).

Why not eliminate the 2' knee wall and increase the pitch to 10/12 or 12/12? The tails of the rafters will be restrained by the floor diaphram and make the whole thing simpler to construct.

[Ismellelephant]

Thanks mjpliv
I've already started the barn and purchased the wood so I think I may be locked into the 2 foot kneewall. I will contact a engineer though, probably stupid not to.