I'm designing a small timber frame cabin comprising of two intersecting gable roofs. I have found lots of good reference on designing the compound joinery put can't find any info (not even a photo) showing the peg detail for a jack rafter tenon to a valley rafter. Should the peg run perpendicular to the valley cut in the valley rafter or should it run perpendicular to the bottom face of the valley rafter? Should the peg go right through the valley rafter (ie: visible inside the structure) or be blind?

First of all, Jim, I really appreciate your thoughtful answers here and the time you take to keep this forum so useful. This is my first post, as I have been awaiting to the reply of this question, for I have the same question.

I am interested in valley framing and have looked at and understand the Hawkindale tables and accompanying drawings on this site. What I have not found is examples of dimensioned joint details (how long is the tenon, how much relish, etc) and where are the pegs located.

Any help would be useful and pointing me too a good reference for valley timber framing (and compound joinery, in general) would be very useful.

thanks
Pete

I personally haven't had a lot of experiences with valley rafters.
I don't have a good answer for you at this time.
Sorry.
I'll try and do some research into this and find an answer.
Jim Rogers

Well, most of you won't like my suggestion... use screws or spikes... Pegs were used originally because it was the material at hand. If traditional framers had power tools and screws they would have loved them. The jack tenons don't need to be long since they are in compression. We use screws frequently in difficult to peg situations, they are also good at pulling a joint together. In a compression joint I don't think the direction of the screw is critical other than thinking about which direction it will pull the joint together. Important design considerations are the location of the tenon with respect to horizontal shear (unless joint is housed) and the amount of material below the bearing surface of the Jack. Also, I would consider engineering more than 50% of the Jack carrying capacity on the valley unless you're confident in the tension connection at the top of the Jack. Of course if it is simply a fork & tongue type connection then you must bring all of the jack's load into the valley. If the jack is secured to a ridge beam at the top, you could screw that as well, making that connection a tension joint, of course you have a pegging option here as well, but it is actually quite rare that one can design a joint with enough relish on the tenon to truly satisfy engineering specs.

Paul,

thanks for the suggestions. I have nothing against screws (or any steel for that matter) as long as they are used in a way that is asthetically consistent with the rest of the joinery. The joints as currently designed is housed 1" plus a 2" tenon which should proved sufficient bearing surface. I am wondering if you have used (or seen, heard...) of Timberlinx being used in jack to valley joint. One other idea is some simpson metal on top of the jack to valley joint (let in slightly so decking planes out properly). This would not help pull the joint tight put would help keep it there (and make the inspectors happy)if used in conjunction with screws. I assume by screws you mean lag screws? My jacks are 6x8 and valley 8x10 or there abouts,

Pete

Gents,

My engineer says the roof decking will hold the jack rafter in place sufficiently. It's pretty small, 4x6 6ft long. I like the idea of a hidden lag/screw to secure it during the assembly though. Thanks for the advice. Good luck with your project Pete.

Dave