Hip valley rafter loading

I have attached a graphic showing the loading on a common rafter and a hip valley rafter. Most of the time the hip valley rafter is the same size as the common rafter. In this graphic the common rafters are 17 feet long spaced at 16" on center. The hip valley rafter is 22’-8" long with the attached jack rafters at 16" on center. The yellow shaded areas show the area loading that is transferred to the common rafter and the hip valley rafter. Just by visual observation you can see the hip valley rafter carries significantly more load than the common rafter. I did the calculations and the common rafter carries 7.42#/linear foot deal load (DL) and 20.48#/linear foot snow load (SL). The loading is based on a shingle roof, 1/2" plywood on #2 D.Fir-L 2x6 rafters. Based on the loading the common rafter without intermediate bracing fails in bending and deflection. By adding a mid-span support the 2x6 common rafter passes. The hip valley rafter failed in all combinations including two 2x12s, which was modeled without intermediate supports. The two 2x12s failed 220% in bending and 6% in deflection.To make the hip valley rafter a clear span beam it needed to be one LVL beam 1-3/4" x 11-1/4" , 2.0E, 2950Fb or two LVL beams 3-1/2" x 9-1/4". Total deflection was 73% of the maximum allowable by code for the single LVL and 65% for the double LVL beam.

I have added pictures of Friday’s inspection where the 2x6 hip valley rafter had about a 4" deflection mid-span. The jack rafters were pulling away from the hip valley rafter due to the excessive deflection. In general the hip valley rafter needs to be one to two sizes larger than the jack rafters, if you can add a few support braces. However there is typically no load bearing wall under the hip valley rafter needed for support. Where the hip roof is attached to the main roof at the ridge board both valley rafters and the hip roof ridge board transfer approximately 2400 lbs. So a vertical support at this point is needed.


Great info, Randy! Thanks! :+1: :cowboy_hat_face:

Thanks again, Randy!

How would the mid-span support be executed without a wall below and single 2x ceiling joists?

Have you done similar math to see how the numbers play out when the hip/cricket is over-framed using sleepers/valley boards over the roof’s sheathing?

PS: does your brain hurt when you do all the funky math (no pun).

Simon, 95% of the time these hip valley rafter braces do not have adequate support, I.e. no load bearing wall under the brace. I have not done the math when the hip roof is built on top of a roof.

So what’s the recommendation and or a fix? leave it alone with 4" deflection?

I recommend a framing contractor install additional bracing, if possible to stabilize in place. Reversing the sag may not be possible. Consult with a structural engineer if adequate bracing can’t be installed or if you decide to replace or strengthen the valley rafter.

I find this very interesting Randy. Thank you for taking the time to explain it. You may continue to elaborate, I’ll get some popcorn and keep watching this thread. :slightly_smiling_face:


Would this fix it? :slight_smile:

As long as the jack was stable on the drywall… :wink: :sunglasses:

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Can’t fix stupid :joy: