Cupola build ?

Getting ready to put the roof on my new 12 by 16 sugar house. My question is about the cupola build. I see some that look like they are just dropped onto the roof with the rafters still in place, and some that appear to be built into the roof. Is one way right ? I feel like it should be built on shortened rafters with a framed sill , like a mini house. Also my evaporator pan is 2 foot by 4. with a 3 by 2 syrup pan. So I planned to make a 3 by 4 copula with drop down doors. Does that sound right. Oh and if your have any framing pics I would love to see them

Thanks

Attachment 21509 I don't know if there is a right way. This is how we did ours.

Old wisdom suggests the open cupola area equals the area of the evaporator. However hoods can reduce that.
In my case, I had a 2x6 evaporator when I built my sugarhouse. I later got my 3x8. My cupola is just 2x6'. My 3x8 has a tight hood on the 3x5 flue pan and a raised hood over the syrup pan, the cupola is plenty big. My sidewalls are 10' tall and my roof is an 8/12 pitch, I don't know how much that might affect the performance. At any rate, my 24 s.f evaporator is happy with a 12 s.f. cupola area. In fact, it's still enough even when I also have my 2x6 finisher running too.

Thanks for the pic thats what I was thinking. So do you count the sq feet of both doors or just the bottom opening leading to the doors. My plan was 3 by 4 giving 12 sq foot on each side for 14 sq foot of evaporator.

Hey Maple Camp
I did a 12 by 14 timber frame shed and mounted the cupola on two 4 by 4's spanning the opening between sets of rafters then set the cupola framing on that and sort of built it in place but if I had it to do over I would have built it complet on the ground then hoisted it up and set it on the framing. Was hard to work on it especially after the roofing was on. Windows open down like a hopper style and total opening equals more than my little 2 by 3 pan. Good luck on your build Jay

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One more pic so you can see how I set the cupola framing on the roof framing Jay

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I would keep the rafter framing through the cupola. As an engineer, I always think about load path - how does load flow thru your structure. Removing the rafters under the cupala takes away the continuity of the load path. Eventually it could cause a sag in the roof. I like Zucker's timber frame which preserves the load path elegantly.

I framed mine to be open to reduce the surfaces for steam to gather right above the pan. Plus I like the way it looks open. It's not wrong to leave the rafters in place, just a preference - less measuring and cutting too. I wouldn't worry too much about load. Not to say load shouldn't be considered, but it can be accounted for. If you frame it right, like a dormer, you are structurally fine.

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Originally Posted by SeanD

I ..,. If you frame it right, like a dormer, you are structurally fine.

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However, you can't frame it like a typical dormer. A dormer gains a lot of structural integrity from the flooring below it. And typically, the dormer is built right out to the top plate of your exterior walls. For a cupula, to achieve the same continuity with the building frame, it would need adequate collar ties at the ends and significant stiffness across the front and back to transfer it's loads to the edge rafters and collar tie frame. Think of the cupala as a floorless structure that will want to spread open at the bottom under load. And the thing about wood is that it creeps under load so you might get enough sag to be noticable unless you take additional measures. This situation is more of a concern with a cupola that extends over multiple rafter and with wider buildings.

Here's my cupola. It's 10 ft long and about 5 wide with 2 drop-down doors on each side. The framing was easy since I maintained the rafters and ridge beam. I used 2x4 (rough cut) studs for the cupola bents. The legs of the bents extend down and attached the the rafters.


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Originally Posted by TapTapTap

However, you can't frame it like a typical dormer.

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Right. I just wanted to make a mental picture. I think no matter what, the building inspector should approve the plan. A building inspector is usually a former builder with a ton of experience and can work with you to answer questions and make suggestions to solve problems. Advice here should be taken with a grain of salt. Let the inspector have the final say. I found the help I got to be well worth the application fee. Besides, if you build it without a permit and anything goes wrong, the first place the insurance company goes is your town hall. No permit? No claim.

Seeing Tap, Tap, Tap's doors remind me of another consideration when sizing your doors. Make them large enough that if you have to shut one, the other side can keep up. Heavy rain storms come in from one side of my SH and it's nice to be able to close that side. Without it, it really does rain in the sugar house.