# Help with barn design



## redhorseshoe (Jan 2, 2016)

Hi all,
I'm planning to start building a 32x36 pole barn this spring to use for hay/animal storage. I have the layout figured out and have a rough list of materials. What I'm struggling with though is the roof design. I know I want a standard gable roof with a 5/12 pitch but I don't want to use trusses to build it as I would like to be able to later add a loft. I've built smaller buildings and just used a ridge beam to support the rafters but at 36' long I don't see that being an option.

If anyone has some information or even links to websites that may help me with this I would really appreciate it!

Thank you!


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## Steve_S (Feb 25, 2015)

I think you may be hard pressed to have the full span open as each rafter would be 19'+. Even using 2x8, @ 20' length, it starts to get a tad "wiggly". You could use a Queen Scissor Truss or a Howe Scissor Truss but that would not give you the loft potential. Alternately, you might consider something like a "room in attic" type of structure like this







Many Truss' can be self-built if you make up a jig to keep things uniform and use the correct plates. 

If you want a loft for storage, plan on building the floor for it as part of the roof structure as opposed to a later add-on which will be more complicated. @ 32' width, it will be tricky as it is unless you want centre posts in the middle of your building.


You have to factor in Wind Loads, Snow Loading and several other things to ensure the strength and durability. That is a LOT of roof and it would get seriously heavy with 1' of snow on it which @ 5/12 pitch wouldn't be in a hurry to slide off.

Below is a link to a Very Handy tool to calculate and plan roofs.
Blocklayer Roof Framing Calculator

With a building length of 36' and width of 32', eave overhang of 2' and gable overhang of 2' the roof is 40' long and 36' wide.
Total roof area = 1560 ftÂ²

Roof angle 22.62Â° (Pitch 5:12)
Overall height above outer wall = 7'- 4~21/32"
Ridge top = 7'- 4~11/32" above top of wall, ridge bottom = 6'- 8~11/32"
Rafter spacing is 1'- 4"

Gable Area (under rafters) = 106.7 ftÂ²
Roof Volume (top of wall/plate to under rafters) = 3840.01 ftÂ³
Roof Volume (top of wall/plate to top of rafters) = 4672.01 ftÂ³
Outside top plate edge to ridge top edge = 17'- 6~11/16"

You need:
1 Ridge @ 40' x 8" x 1~1/2"
56 Rafters @ 19'- 8~17/32" x 8" x 1~1/2"

Ridge + Rafter Cubic = 95.31 ftÂ³


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## TnAndy (Sep 15, 2005)

You can use a ridge beam, that sits under the rafter peak, or a ridge board. A ridge beam will provide 'some' support, but really in most designs is not needed. A ridge beam gives you something to set the rafters on, but once the rafters are on, you could go in and saw out the beam, and the roof would still stand.

And a ridge board doesn't do anything but tie the rafters together running the 36' length....it doesn't have to support anything. The pressure of each pair of rafters makes them self supporting. The ridge board merely keeps the rafter pair separated by whatever distance you pick (16", 24", 32", etc) to set the next pair of rafters down the roof. You have to prop up a ridge board while you start installing your rafters to it at one end, but as you get to the other end, you pull the prop out.

What that means is you can have a 32 x 500' building if wanted. Start with 2x6 or 2x8 rafters, that depends on what kind of live load you want on the roof. Snow country, for example, you'll want a taller rafter for a 16' span....maybe 2x10. Spacing, pitch/slope, species and grade of wood all affect rafter sizing.

Then for a ridge board, put a 2x one size taller than the rafter. 2x6 rafter ?, use 2x8 lumber for the ridge board. This gives you full contact with the end of the 2x6 cut at the angle of your slope. 

Use a 12' 2x8. When you get to the end of that 12' board (say 7 pair of rafters on 24" center), simply nail another 12' board for your ridge and keep on going. I use a piece of 3/4" plywood 6" or so wide by 22 1/2" long (the space between rafters on 24" centers using dressed lumber). The last part of your ridge (assuming zero gable overhang) will be another 12'....making your 36' building length.

Do this, you can make your roof any length you want.

Here is a photo of a rafter roof using a ridge board. In this case, I used 2x6 rafters on 16" centers on a 6/12 slope. My ridge board ran from the chimney to the 2x6 prop you see tied into the old roof (look close, you can see the joint....my plywood tie is on the other side of the ridge board). The remaining length of ridge board runs from that prop to where it ties into the old roof. I simply left the prop as extra support since that is just 'dead space' to me where it is located. I did need to box around the chimney flue in the far end of the gable.

Then I used 1x6 lumber for roof decking.


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## TnAndy (Sep 15, 2005)

I used rafters in the above situation for a couple of reasons. One, it was easier to haul individual pcs of lumber up there and build it in place....I had zero access around the addition on the ground (you'd have to see it to understand). Two, one side had a large overhang over a deck the other side did not, which could have been done with a truss, but it would have been sort of odd.

BUT for conventional building like you are building, a truss like Steve suggests is actually better suited for your needs.

I've built plenty buildings, and a lot of 'homemade' trusses. A simple 'king post' style truss has quite a few advantages over a rafter system.










With a rafter system, on a 32' wide building, that "tie beam" (usually called the lower cord on a truss) is a ceiling joist on a raftered roof. You have to have a support wall running down the center (or close to it), bringing a 2x6 ceiling joist from the outside wall to the center wall, then another to the other side. That center wall often limits what you can do with the floor design below. IN the case of a hay barn, you'd probably want a great big open 32x36 to stack and move hay anyway you want.

A truss roof is self supporting, therefor any walls between the outside walls are optional.

Another advantage of a truss roof is you can assemble the trusses on the floor of the building, then hoist them up already done....simply tack a board across them to hold once you have them space correctly, and put them all up, then put your roof sheathing on.

Another advantage is you can use smaller lumber. Those "stuts" (the king post, and the two angled supports) are much stronger than a rafter (the angle struts cut the span of the rafter about in half, for example)...meaning you can cut lumber size some, and save money.

I use plywood plates for my homemade trusses instead of the metal plates. Nail LOTS of 4-6p nails, and construction glue. Plates go on both sides except the gable end truss, I only do the inside.

Lay off your truss on the wood floor, then nail wood blocks to build a jig, and every truss comes out the exact same.

As for storage room....well, honestly, with a 5/12 slope,you are not going to have much space up there to begin with. The height in the center of the roof is only going to be 5x16=80"......4' out from center, you're down to 60"


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## andrew3d (Jun 23, 2002)

With a 5/12 pitch you will not have much room up there anyway.
But I have built my own pole barn and I set poles down the center to support my ridge beam. It's just an idea of what I did to share with you. 

A photo that shows what I am saying is just below.


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## coolrunnin (Aug 28, 2010)

I like a lot of the plans these guys have for various designs.

http://bioengr.ag.utk.edu/extension/extpubs/planlist97.htm#General Barn and Utility Shed Plans


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