16' x 24' Mini-barn plan revisited

[Badfish740]

I had been fooling around with pole barn ideas a while back and then the wife told me she was pregnant , so I got a little distracted for about 9 months. Now the little bundle of joy is here and I'm once again thinking about building something next summer. I basically figured out that for a structure this small, pole construction really doesn't make sense from a cost perspective, so I'll be stick framing this one, with a few twists... Basically I'm looking to create a 16' x 24' shed with a loft (10' x 16') at either end. The lofts will not only provide storage, but hopefully tie the walls together, since the braced rafter design of the gambrel roof with be imparting thrust on the walls. They'll also be balloon framed in so as to provide more headroom up top:

I showed this drawing to my local code inspector whose reply was "Yup, looks good." I want to be sure that I'm designing a building that is going to be strong and long lasting, so I'd like a few more eyes on the design. I should mention though that the braced rafter design is a copy of what many shed companies/kit suppliers use in my area. Using 2 x 6 rafters and (in my opinion) very small gussets on only one side of the rafter, they rate them for 30lbs/psf snow load and 90 mph wind load. My gussets will be 3/4" plywood on both sides with the 2x6 sandwiched in between and will also be a great deal larger. I could also upgrade to 2 x 8s for not much more money. Does this look like a solid design?

 

[ironpony]

looks great overall, the only concern I would have is;
the connection of the roof truss to the top of the wall, normally that would be where the "loft joist" bottom chord sits. You have lowered the "loft joist", so there is no bottom chord tying the truss together. any load will be spreading the roof truss, it is not actually tied together. I see why you did it that way for headroom but it is not structurally sound as is.

 

[Badfish740]

looks great overall, the only concern I would have is;
the connection of the roof truss to the top of the wall, normally that would be where the "loft joist" bottom chord sits. You have lowered the "loft joist", so there is no bottom chord tying the truss together. any load will be spreading the roof truss, it is not actually tied together. I see why you did it that way for headroom but it is not structurally sound as is.

I struggled with this in terms of how much of a factor it would be. I guess an engineer is really the only person who can say for sure. My reasoning is that the truss is pushing outward on the wall, but that the "lever arm" (the portion of the wall between the loft joist and the top plate) is not very long, and therefore the loft joist would still serve to tie everything together, the question is how much force can it resist?

 

[ironpony]

I agree with your thought process and it is valid. My concern is the connection of the truss tail to the top of the wall. Your walls will not move with your design, they will actually be very strong, the truss tail is going to want to push off the top of the wall.

 

[Badfish740]

I agree with your thought process and it is valid. My concern is the connection of the truss tail to the top of the wall. Your walls will not move with your design, they will actually be very strong, the truss tail is going to want to push off the top of the wall.

Got it-you can't see it in the drawing, but I had intended on birdsmouthing the rafters where they connect to the top plates for that reason:

Does that look like it will work?

 

[ironpony]

excellent, you will have zero problems. you might be able to use hurricane straps with that design or added strength.

 

[Badfish740]

excellent, you will have zero problems. you might be able to use hurricane straps with that design or added strength.

That's a given-can't have the roof flying off Wizard of Oz style if we get another Hurricane Sandy!

 

[semipro]

What are you planning for roofing and sheathing?
Off hand, I'd worry that your roof design provides no protection for the siding or fenestration.

Edit: How the heck tall are you? Seems like you have a lot of headroom in the loft especially when you consider that most items stored will likely go against the side walls/roof.

 

[Badfish740]

What are you planning for roofing and sheathing?
Off hand, I'd worry that your roof design provides no protection for the siding or fenestration.

Right now the plan is for steel roofing and a composite T-111 like product called "Smart Side", which is basically OSB pressed on one side to look like T-111 and pre-coated at the factory with a heavy duty primer to withstand exterior use. The OSB itself also has some anti-rot agents added to it which apparently work very well as I tested them by happenstance. I had bought a few sheets to dress up my old pallet woodshed and left a 2x4 scrap piece sitting behind it in the mud for two years. When I finally tore the old shed down I found it, completely intact, no delamination, etc...just a little moss growing on it. I figure if I put it up on a building and actually take care of it, it will last quite a long time. I tweaked the rafter/truss plan a bit and decided to go with 2x8s instead. They give me more of a birdsmouth inboard of the top plate, and enough outboard to do a small soffit. The overhang will be about 9". At the bottom, a PT 2x12 will be run around the entire perimeter as a "splash guard," and the entire building will be surrounded by gravel so as to minimize rain/mud splattering on the siding:

Edit: How the heck tall are you? Seems like you have a lot of headroom in the loft especially when you consider that most items stored will likely go against the side walls/roof.

LOL...Ok, confession time. Though I do need the upstairs storage, I'm likely not going to need as much (two 10' x 16' lofts) as I'm building. However, the building will not hold together without them-the loft joists will be tying the walls together and resisting the horizontal forces imparted by the rafters, so it's not like I could omit one of them. One of them will be packed to the gills with Rubbermaid tubs, the other? Well, let's just say that with a wife and two daughters and a small house, sometimes a guy just needs a "man cave" The other loft will end up being some combination of storage, a couple of stools/chairs, maybe a small card table, and some sort of liquor cabinet. Over time I may develop it into more once I run electric out there, insulate it, and find a way to heat it that my insurance company will allow.