Gambrel Roof Detail Question

[Dennis Putnam]

I am going to be building a small barn with a gambrel roof to give me room for overhead storage. I understand the basics of building the trusses but could not find much on some details with respect to the joist interfaces.

I am thinking that the joists would be flush with the outside of the walls (20' outside wall dimension means 20' joists) and simply sitting on top of the plates. The gambrel truss overhang would then simply be a function of where I place the seat cut. If that is correct is there a rule of thumb for how far up to place the seat, or how much of the truss should extend beyond/below the joist? Or is it just a matter of aesthetics? What should I use to attach the joists to the walls in this case? I have been looking at Simpson strong-ties but from the pictures it is not at all clear which I should use for flush joists sitting on top of a plate. Finally, are the splicing plates for the trusses really worth the cost (both sides?) or is old fashioned toe nailing just as good?

Thanks.

[Steve Rozmiarek]

Dennis, the gambrel roof barns I have been around have the trusses sitting on top of the plate, no overhang. The overhang is from a tail that is attached to the truss someplace above the plate, placement of your choice, and hanging outside of the plate. This gives the roof one more profile angle too. Personally I would just use a plywood plate on each side of the truss connections. The Simpson stuff is ok too, but you will want something to strengthen it up for installation. Toe nails are floppy connections. I like to use those hurricane ties for connections of the truss to the plate. Toe nail of that is also common.

[Michael W. Clark]

I built a smaller version of what you are talking about at our last house, more of a small garden shed about 10x10. I would agree with Steve about toenailing the trusses. I used 1/2" OSB for the splice plates on both sides. Mine was small enough that I built a jig in the garage floor to get all the trusses the same. I imagine you could do something similar on the pad or ground. Like I said mine was small and I used 2x4s for the trusses, but it was plenty strong. I could walk on it with a lot of wood stored in the ceiling as well. Not saying you should use 2x4s for your size! But just illustrating the strength of the design. My trusses were toe-screwed into the top plates of the walls.

Mike

[Thomas Canfield]

Dennis,

My new shop is 16'W x 24'L with Gambrel trusses for roof. I have 6" overhang each side to allow for air vents under the 6" "eave" . I have a 4' H x 10' clear opening down the center and one end truss is framed for a 5'W x 4'H opening for a door. I installed a drop down attic stair for access and used 1" decking in the open space which was designed for a uniform load to allow for storage. The trusses are on 24" centers. I gave the information to truss supplier and they designed, faabricated, and delivered the trusses to site for a reasonable price considering material and contractor doing the work. I suggest you make a sketch showing the dimensions you want and loading and then go get prices for prefab trusses. They will also give you the weight for the trusses, and it was all 3 men wanted to do to install the 16' without some mechanical help. Just sharing my experience.

You did not give your location, but tie-down straps may be required due to local building codes or for wind. They don't cost that much and add a lot if you even think there may be some high winds.