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Feedback on frame design

Started by Woodland Dave, January 17, 2020, 08:02:07 PM

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Woodland Dave

I'm looking for a little feedback on my fame design. My main question is: can I build a frame like the one pictured below and stick frame or use trusses for the roof. A potential problem I see with it is the bents with the plates are really far apart. The design sort of leaves a bent out of the middle. In making this design I assume that stick rafter ties would fulfill this roll.

There are two reasons I've come up with this design: First, I want to keep it relatively simple as it will be my first build. Second, I'm limited by length of timber I can harvest. I'm hewing all the timbers (white ash) and most are around 10', a few 12', and luckily some 15-16' i plan to scarf together for the plates.

I don't have the exact dimensions figured out for beam and post sizes but in this drawing the whole structure is 24' x 24', the posts are 8" x 8", and the beams are 8" x 10".



 

Don P

Trusses would be no problem, stick would likely be an issue if there is nothing in the center to bear and splice the rafter ties/ ceiling joists together over. The building inspector will likely want beam splices over posts. I've been talking to another member who had to forgo scarfs for splicing over posts to satisfy inspections.

paisan8

run two middle posts high to hang a ridge beam on that will hold the rafters or use collar ties . might get away with one heavy duty tie in the middle maybe 2/3 down from the top.

jim

Woodland Dave

Thanks Don. I've had a tough time trying to design something myself with limited experience. I want to make sure my plan is pretty close to working out before I talk to an engineer if the need arises. Most timber frame designs I've seen for larger structure makes use of much longer timbers. That's why I've opted to go for a hybrid style where I can bypass using longer timber ties. Though it'd be way nicer to have a full timber frame, with the shorter length timbers I have access to it feels like I'd have an excessive amount of bents. I hope this makes sense.

What exactly do you mean by beam splices? Could you link to the post you mention? A friend of mine's dad just built a 16' x 24' timber frame cabin for her. Her dad also happens to be the building inspector for their town. The way they have the partition walls set up you can't see above the middle posts on the side walls so I asked her if there were joints up there. She said she thought they just butt together. I doubt its a simple as that because the other stuff her dad does is pretty incredible but it made me wonder if i could avoid scarfing the plates. Reason being in the Jack Sobon book I have he says to make the scarf 30" long. For me and my shorter length ash trees It will be tough to get four 15' timbers for the two 24' plates. So if there is an alternative it could help me out.

BTW the solubor treatment you advised me on late last summer is keeping the bugs out of my timbers effectively. Firewood I cut of a few months prior is covered in holes and sawdust. Thanks for that!


Woodland Dave

Jim, thanks for the input. I'm considering a few ideas like you mentioned. Any thoughts on how to support a ridge beam other than making the posts longer? I'm limited in timber length.

Don P

The borate is good stuff, glad it worked for you.

The scarfing woes were in a series of pm's. I actually side more with the building code there. It requires that beam splices occur over posts. There must be some means of connecting beams to the posts well enough to secure them in place and handle any uplift. Typically they are butted over the post and a hidden T plate is lagged to everything. I think you could size the beams using the code referenced "Wood Structural Design Data". You might need a grader but I think we've avoided the engineer's fees thus far.

A structural ridge beam 24' long is likely a glulam or built up lvl's. Those components, like trusses are provided with engineering of the component as part of the sale. Rafters hang from the ridgebeam providing for an open cathedral type ceiling.

For a prescriptive stick framed ridge board roof without a heavy ridgebeam, rafter ties would be required across every rafter pair. In the codebook they must be no higher than the lower third of roof height. Using the code referenced "Wood Frame Construction Manual" you can probably get them up as high as the middle of roof height.

Collar ties are another animal, they are required in the upper third of roof height to hold the rafters together at the ridge, they can be replaced by steel strapping over the ridge and down into each rafter, for instance in that open cathedral.

cib


The code enforcement recommended strong tie CPTZ between the post and at least one beam if not both and another between the two tie beams instead of the scarf. Where I'm building my barn/workshop will be visible from several neighbors so I figured it best to at least get their blessing before building. I didn't want someone reporting it later and causing issues, since it is AG it should be exempt but I've dealt with neighbors that caused trouble at my house in Indiana so an ounce of prevention.

Woodland Dave

@cib I appreciate the feedback as I haven't found a lot of info online about using the various simpson products. I looked up the CPTZ strong tie and it looks like a component for attaching the post to the slab. I don't understand how it would be used in place of a scarf. Can you elaborate on what you mean?

How annoying that your neighbors still cause trouble despite you being the ag zone. I've got one nosy neighbor who seems to come over every time he hears me hammer one nail. I understand your motive for getting the "blessing". There's peace of mind in knowing your following regulations where no one can mess with you.

cib


Woodland Dave

@cib Thanks. Would it look something like this?

 

cib

Quote from: Woodland Dave on February 04, 2020, 10:00:34 PM
@cib Thanks. Would it look something like this?




That's correct. It looks similar to what the timberlinx layout would be just you're using the strong tie instead. The local inspector preferred it over a scarf joint. This is the more traditional framing method used in "modern" framing so he felt OK with it.

Mine is a polebarn build but due to concerns about neighbors and possible complaints I mentioned it to the coding office. He wanted to take a peak at my plans before hand. 

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