Timberframe Sugar Shack

[shackbuilder]

Hello everyone, new to the forum, and my first post. I am looking forward to tapping into the great wealth of knowledge here. I am an experienced woodworker, and carpenter, and have had a hand in the assembly and raising of one two story timberframe.  I make Maple Syrup in upstate NY, Helderberg Mtns, and I am getting ready to put up a timber frame Sugarhouse. I'll be getting locally milled White Pine, and doing the joinery myself.  I have a good idea of what i want to do, and have seen some photos of frames that look like what i want.  I would very much appreciate any opinions on as to if this is possible or not.

  First of all, as I said the frame will be white Pine, 24 x 36, three 12' bays, one story, with a steep roof 10-12 on 12, with common rafters.  My First question is, can i span 24' with a tie beam, i need a clear span as the evaporator sits in the center, if so, does this need to be a giant beam or is an 8x10 adequate, the posts will be 8x8.
  Second is on the rafters, id like to do 3' spacing, tongue and fork with no ridge beam, and have at least a 1' overhang. Is it possible to do this without collar ties? Where can i calculate what i need for rafters, is a 4x6 adequate?  I'm thinking a 12/12 with steel roofing isn't holding much snow.
 
  I also need a coupala for the sugar shack look, and steam venting if i dont go with hoods on the pans, it would be 12'long and 4' wide, so i'm thinking 2 sets of heavier rafters headered/purlined to each other to carry the three cut rafters, and the coupala.

I'd love to hear any input before i start sketching, also having trouble finding any local timberframe savvy engineers. Thanks in advance for your input.

https://forestryforum.com/gallery/albums/userpics/41855/sheds2.jpg

[witterbound]

There are some calculators on this that can help.  You will need to hire an engineer to be sure.  24 foot clearspan sounds awful wide.

[shinnlinger]

A hammertruss would work really well. It gives you the vent and the span. 

[Brad_bb]

24 foot clear span can be done.  You don't have a second floor correct?  You wont have a loft correct?  You could do a queen post or a king.  Hammerbeam bents are extra work and you usually need a steel tension rod in them anyway so you're really not gaining clearance.  A queen will usually give you more compression joinery which is good.   3 ft apart for common rafters is too far in my opinion.  You can do 2ft with the right sizing.  I HIGHLY RECOMMEND you use an engineer (Fire Tower engineered Timber is the only one I know) to size beams and analyze the structure.  They'll take into account your roof pitch and snow load for your area as well as the strength of the timber species you're using. You need to be able to visually grade the timbers you're using(assuming your county doesn't require a grade stamp).  You're horizontal beams and rafters are most critical.  Lastly your joinery needs to be proper.  The engineer will likely not go into that with you.  Sometimes engineers will over engineer in certain areas to be sure they are safe.  They will sometimes want to add metal in the frame so they know they are covered.  My last frame had some 22 ft top plates that were changed to 24 ft (extended room length).  The 8x8's that were already ordered would have needed steel angle iron.  I didn't want that so instead we agreed that 10x10's would work without metal, so I ordered the additional material.  This was oak by the way.

So what I would really recommend is that you find a good timberframer to work with on the design and have them work with the engineer.  It will save you time and trouble.  You should also have the engineer spec out the foundation - footer, stem wall, rebar amount and sizing, slab specs, what PSI concrete to use for each.  Are you going to use simpson straps wet set in the concrete to attach to the timbers?  Timberlinx can also be drilled and epoxied in after the fact.  You may want an interior ledge on the stem wall for the slab to rest on.  Don't forget that you need blockouts at the top of the stem wall where you'll have any doors so in those locations, the slab is poured over the stem wall giving you a clean looking continuous floor. 

[shackbuilder]

  Thanks for the opinions so far, I am open to using a bent/principal rafter/truss system with purlins, but most of the joinery details i see at the rafter to top of post connection do not include an overhang, can this be done with a purlin out on the overhang to support roof decking?
  Brad, as far as the foundation, its already in, poured an alaskan slab on new years eve while the weather was cooperating. Concrete is mainly what i do for work, so I get some leftover material now and then. It's a 24x36 slab of 4000 psi concrete, with about a 16"x20" thick haunch around the perimeter, 6" thick in the field, with a grid of #8 rebar, and #8 rebar down in the haunch.
  I was thinking of setting the posts on a PT 2x bottom plate that runs the perimeter and acts as the bottom siding nailer for board and batten.  Plate is held down with j bolts, and posts will be stub tenoned into it, with  steel strapping sandwiched under plate and coming up fastened to the posts.

[timberwrestler]

You can span 24' as a roof truss without any problem.  If you expect to add any floor load upstairs, then you're asking for some more difficulty.  A truss is inherently a principle rafter type of timber frame.  You could then go with common purlins over the principles (top chords).  Or for a more European look (which I like), you could add a principle purlin to break up the span, and have common rafters between the principles.  I'm nearby in the Berkshires, so I'd be happy to help.  I've done one TF sugarshack, but had all sorts of curvey stuff in it.  Feel free to get in touch with me via the link below. 

[GAB]

Shackbuilder:
Generally speaking the length of the stack is twice the length of the arch.  If your walls and roof are too high requiring more chimney, then you could have too much draft, and if you are burning wood as a fuel then you could get some pretty good size sparklers escaping and possibly catching the woods on fire.
Just a word of caution.
Gerald

[shackbuilder]

 Gerald, current evaporator is 3 1/2 x 14' so 28' of stack off the evap at 3' off the floor puts the stack at 30'+,  I'm looking to get 8' clear under my tie beam, so 10-11' to the top of plate beam should be a roof peak height of around 23',  It'll be a fun smokestack to put up, ha.

[GAB]

Gerald, current evaporator is 3 1/2 x 14' so 28' of stack off the evap at 3' off the floor puts the stack at 30'+,  I'm looking to get 8' clear under my tie beam, so 10-11' to the top of plate beam should be a roof peak height of around 23',  It'll be a fun smokestack to put up, ha.

Not knowing how high your sidewalls were intended to be I thought that I should warn you about that small issue.
I know of one place where the boys added an extra 4' to the stack for a 5' x 14' evaporater and had to shut down wait for things to cool then remove 4' of stack and fire up again.  Large sparklers were going towards the neighbor's dairy barn.
As an added tidbit: sugarhouses work best if the spine of the roof is predominately in a N-S direction, unless you are using fans to move the steam. One fellow did his E-W and when the sun goes down the steam does not rise for some reason and I do not understand it.
Gerald

[Jim_Rogers]

can i span 24' with a tie beam, i need a clear span as the evaporator sits in the center, if so, does this need to be a giant beam or is an 8x10 adequate?

As mentioned if there is no loft or any weight stored above the tie beam then you most likely could span 24' with an 8x10.
However if you're going to do a king post truss or a queen post truss then you're going to have your design reviewed by an experienced timber frame engineer.

Most of the people who I have helped with a "sugar shack" have made the vent at least equal to the size of the evaporator or bigger.
Knowing that you intend to do a copula vent you're going to need to have heavy rafters supporting the copula posts. If these rafters need support, like queen posts, then the tie beam may need to be bigger.

It is my opinion that most timber frame experienced engineers "are" familiar with joinery. And they can advise you about your frame design.

Second is on the rafters, id like to do 3' spacing, tongue and fork with no ridge beam, and have at least a 1' overhang. Is it possible to do this without collar ties?

Very difficult to say without know the snow load for your area and seeing the complete design. Collar beams are usually on end pairs of rafters for siding to attach to in order to span from tie beam to rafters. However, then can be sometimes needed mid roof to help support the rafters. Again depending on the loads. With a copula you may need some.

Where can i calculate what i need for rafters, is a 4x6 adequate?

There are some "beam" calculators in the red tool box on this site but your design could be complex due to the copula so 4x6 rafters may not be large enough. Again it depends on the snow load, type of roofing materials, and maybe even some other factors like exposure to wind load.

As mentioned there are experienced timber frame engineers available. One that I use is Fire Tower. There is a site where you can search for timber frame engineers. Here is a link:
http://timberframeengineeringcouncil.org/

Good luck with your project, and keep asking questions.

Jim Rogers

[canopy]

Not necessarily in this case, but what often happens is builders without proper knowledge will beef up areas that don't need it which is wasted material doing nothing and at the same time not have a good enough understanding to see the actual weak spots which get no attention. So instead of looking at just a few spans that come to mind, get an engineer to review the frame in its entirety. Cost is reasonable, it's quick and easy, you don't have to go anywhere, and answers are simple and sound. Just the peace of mind can be worth a lot. Fire Tower is fantastic to work with and am sure others are as well.

[timberwrestler]

Jim,

Since the TFG merger, that link to look up an engineer is a little different than before.  It now goes to the TFBC site, so it will only show engineers that are members of the TFBC--pretty useless.  It used to list all of the member of the TFEC.  I wrote an email to the Guild a while ago about it, but haven't heard anything back yet.  If you know the right person to bother, feel free to hammer on them.