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Frame Design for a Chicken Coop

Started by kreyszig, July 18, 2018, 10:40:31 AM

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kreyszig

So I have a chicken coop I am working on (my first framing project) and I am not quite sure about the optimal joinery design for the frame. In particular, my concerns are more related to the frame of the run, since it can only rely on the integrity of the frame joints to stay straight. The coop would be 8' wide and 40' long, with posts every 4' along its length. The posts would be about 8' tall. The roof has a pitch of 45 degrees (I plan to use it to support solar panels in the future). I live in eastern Ontario, so there can be a good amount of snow in the winter. Here is how I see it so far:



My plan is to use 4x4 Douglas fir for the posts and the plates, and prefab trusses. I would use 4x4 treated wood for sill beams (not shown) over a concrete foundation. I would like to use mortise and tenon joinery between the posts, sill beams and plates. For the braces I was thinking of using 2x4 (or 2x6?) along the length between the posts and the plates, using mortise and tenon joinery as well. However, I am not quite sure what to do for braces in the other direction (between the posts and the prefab tie beams which would presumably be 2" thick), as the tie beams could be too thin for mortising. From a practical point of view, I am not quite sure if wood braces between the posts and the tie beams are such a good idea, because I have concerns that chicken would want to use them as roosts, and I want to avoid droppings on the frame, so I am wondering if using some steel cables would be preferable. Finally, I am not sure if I should simply nail the trusses to the plates, or if I should create shoulders at the ends of the tie beams for better stability.

So basically I would like to know if I am doing anything stupid here and would appreciate advice about the components I am not quite sure about. For the frame I am looking for a time and cost effective design, which does not compromise structural integrity. Please let me know!

Thank you!

Ljohnsaw

I would say the frame is too small to do traditional timber jointery.  The 4x4 posts just don't have enough meat to cut into.  I would think about all you could do is use 2x4 for the braces and half-lap them (1" into the 4x4, cut the 2x4 down to 1" at the joint) to the 4x4 posts so as to not weaken them too much.  Also, since the posts are only 4 feet apart, that means your braces are pretty short (looking at your picture).  The shorter/closer in the braces are to the post, the weaker your frame.  It provides more leverage and would likely break your post/beam apart.  I would shoot for something larger like 3 foot horizontal/vertical that the brace spans.

For the bracing going the short direction and the potential roost problem, why not just add a plywood gusset to fill it in.  You would only need that on every other or possibly every third span.  On the truss attachment, again, you don't have a lot of wood to notch.  I'd just use a Simpson bracket (hurricane) to nail then on.

Will there be a ceiling?  If not, what's to stop the chickens from roosting up on your trusses?   I suppose you could just use chicken wire to prevent them from getting up there - and on the braces as well instead of plywood.
John Sawicky

Just North-East of Sacramento...

SkyTrak 9038, Ford 545D FEL, Davis Little Monster backhoe, Case 16+4 Trencher, Home Built 42" capacity/36" cut Bandmill up to 54' long - using it all to build a timber frame cabin.

kreyszig

Thanks ljohnsaw,

Good idea about half-lapping. What would use use for the tenon length/mortises depth then?

Regarding the braces along the length, initially they were longer so they connected at 2/3 of the post height, but I used to have them at every post, so braces for adjacent posts were overlapping. Since you mentioned having them longer, I assume you agree with the current design I have where these braces are every second post then?

For the braces in the other direction, I sure could use bird netting like I planned using for the "ceiling". The braces would be half-lapped into the post. I could cut a shoulder in the tie beam for the other end and use a Simpson tie between the beam and the brace. Any reason for the hurricane tie instead of a flat tie?

Regarding the joints between the posts and the plates, and the posts and the sill beams, do you have any advice?
Finally, should I use scarf joints for the plates and the sill beams?

Thanks!

analog animal

Hi Kreyszig

Here are a couple photos of a workbench I did out of 4X4s and 2X6s using mortise and tenons. As you can see some of the tenons are long, skinny, and awkward. I can stand on it no problem - so it's plenty strong for a work bench. Maybe this gives you some ideas



 



 

Roger Nair

Kreyszig, I would seriously consider using conventional 2 x 4 and nail construction or pole barn technique, if time and labor is in short supply.  The truss detail of an eight piece truss to span 8 feet is not an efficient design.  A ceiling joist and two rafters are likely minimal but adequate for roof structure.  Stud walls 24 oc with overlapping double plates should be adequate for walls.  Walls can have let-in 1 x 6 braces from plate to sill.  Plywood or osb sheathing on the roof will make the whole building rigid.  

I would also check for a provincial ag dept, regional ag college or public library that could have a plans for farm buildings. 
An optimist believes this is the best of all possible worlds, the pessimist fears that the optimist is correct.--James Branch Cabell

kreyszig

Quote from: analog animal on July 18, 2018, 04:13:41 PM
Hi Kreyszig

Here are a couple photos of a workbench I did out of 4X4s and 2X6s using mortise and tenons. As you can see some of the tenons are long, skinny, and awkward. I can stand on it no problem - so it's plenty strong for a work bench. Maybe this gives you some ideas
Thanks. I did not intend to have tenons going through the whole mortised pieces though if possible...

kreyszig

Quote from: Roger Nair on July 18, 2018, 06:24:57 PM
Kreyszig, I would seriously consider using conventional 2 x 4 and nail construction or pole barn technique, if time and labor is in short supply.  The truss detail of an eight piece truss to span 8 feet is not an efficient design.  A ceiling joist and two rafters are likely minimal but adequate for roof structure.  Stud walls 24 oc with overlapping double plates should be adequate for walls.  Walls can have let-in 1 x 6 braces from plate to sill.  Plywood or osb sheathing on the roof will make the whole building rigid.  

I would also check for a provincial ag dept, regional ag college or public library that could have a plans for farm buildings.
Thanks Roger. About the trusses on my drawing, I might have gone over-board with the design. Since they would be prefab I was going to let the manufacturer deal with these calculations, given the anticipated snow load and dead load from the future solar panels. I would just want to make sure that the depth of the tie beams is sufficient if I want to cut shoulders in them for braces and that the position of the truss pieces allow for it as well.
For the roof I was going to use 2x4 purloins every 24" and 26 Ga steel roofing with ribs, to mimic my garage that seems to be holding well. I would also add braces between the trusses. So I was not planning to use sheathing.
About plates, I agree that overlapping double plates would simplify the design quite a bit, instead of making scarf joints to join 4x4 plates. I don't quite understand what you mean by "Walls can have let-in 1 x 6 braces from plate to sill" though?
Thanks!

Ljohnsaw

Quote from: kreyszig on July 18, 2018, 03:54:16 PM
Thanks ljohnsaw,

Good idea about half-lapping. What would use use for the tenon length/mortises depth then?
I would suggest only about 1" cut all the way across the 4x4 and lessen the 2x4 down to 1" to fill that lap cut.  No reason to make it short and harder on yourself.  Now, if you have the two braces coming to a V on the 4x4, then just make them butt up to each other and you can trim the bottom of the V off a little to make the "mortise" cut a little easier.
Quote
Regarding the braces along the length, initially they were longer so they connected at 2/3 of the post height, but I used to have them at every post, so braces for adjacent posts were overlapping. Since you mentioned having them longer, I assume you agree with the current design I have where these braces are every second post then?
Yes.  When I first looked at it, the angle made it appear that there was a brace at every post which would be way overkill.  Also, I would do the half lap on the inside for the braces.  For the top plate, there is no load between the posts to speak of.  So I would use a 2x6 (on edge) here.  The top 2x6 "beam" I would fully let into the 4x4 on the outside.  Then the brace would be nailed to the inside of the 2x6 without cutting into it and weakening it.

Alternatively, you could do a SINGLE brace on every post or every other post all going the same direction except for the end.

Being the chicken run, I'm assuming the "walls" will just be chicken wire - so stud walls would not apply to your build.  You said you want a concrete foundation so really you don't need a sole plate.  I would just use Simpson 4x4 post anchors that attach to the concrete with a single J bolt.  A treated 2x4 could be placed on the concrete (liquid nails?) so you have a bottom nailing strip for your chicken wire.

Just some random ramblings...
John Sawicky

Just North-East of Sacramento...

SkyTrak 9038, Ford 545D FEL, Davis Little Monster backhoe, Case 16+4 Trencher, Home Built 42" capacity/36" cut Bandmill up to 54' long - using it all to build a timber frame cabin.

kreyszig

Quote from: ljohnsaw on July 18, 2018, 07:31:35 PMI would suggest only about 1" cut all the way across the 4x4 and lessen the 2x4 down to 1" to fill that lap cut.  No reason to make it short and harder on yourself.  Now, if you have the two braces coming to a V on the 4x4, then just make them butt up to each other and you can trim the bottom of the V off a little to make the "mortise" cut a little easier.
Sorry for the stupid question, but when you mention 1" cuts, I assume you mean 3/4" and not a true 1" since I am dealing with dimensional lumber and not green timber?

About the half-lap joint though, wouldn't it significantly weaken the post as opposed to using a 1" thick mortise?
QuoteWhen I first looked at it, the angle made it appear that there was a brace at every post which would be way overkill.  Also, I would do the half lap on the inside for the braces.  For the top plate, there is no load between the posts to speak of.  So I would use a 2x6 (on edge) here.  The top 2x6 "beam" I would fully let into the 4x4 on the outside.  Then the brace would be nailed to the inside of the 2x6 without cutting into it and weakening it.
Yes I agree about the top plate, and I like the idea of a 2x6 on edge. This would help stabilizing the posts as well. I would prefer having the 2x6 beam on the outside though (aesthetic). Why do you prefer it on the inside? If I used mortises in the posts, with the cuts off-center such that the outside face of the brace line up with the outside face of the posts, I could still nail the braces to the 2x6 beam? That would make the shoulders of the half-lapped braces to rest against the side of the posts though, I am not sure if it could be an issue?
QuoteAlternatively, you could do a SINGLE brace on every post or every other post all going the same direction except for the end.
Yes I could, but I am not sure I would like the look of it too much...
QuoteBeing the chicken run, I'm assuming the "walls" will just be chicken wire - so stud walls would not apply to your build.  You said you want a concrete foundation so really you don't need a sole plate.  I would just use Simpson 4x4 post anchors that attach to the concrete with a single J bolt.  A treated 2x4 could be placed on the concrete (liquid nails?) so you have a bottom nailing strip for your chicken wire.
Yes the "walls" would just be hardware cloth.
I do not "want" a concrete foundation, but there is a lot of shifting wet clay in my area and the soil where I want to put the coop is only 2' deep. The frost line is probably more like 4' deep, so the dirt must freeze right down to the bedrock in that location. My idea was to remove the clay down to the bedrock, bring in some rocks I have on my property that were taken from the fields in the past and put them around (maybe 1.5' high). Then I would add some gravel to fill in the voids and make the ground level. I would compact the gravel and pour a concrete foundation (no footing) 8" wide and maybe 16" deep. I am a bit concerned about the work involved, but to me it seemed to be the best way to get a solid base on which to raise the building?
The foundation would allow to create some space between the wet ground and snow and the sill. I need something to nail the hardware cloth to like you mentioned. I have seen these 4x4 post anchors, but I am concerned they would corrode due to the ammonia-rich chicken droppings. It looks like it can corrode galvanized steel. Maybe the height of the foundation would be sufficient to create some space between the droppings and the anchors, but I am not sure...

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