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Budding homesteader
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I need help with structural planning of a 32' x 32' pole barn with gambrel roof. I hope my description is clear enough; if not please ask for clarification. If I need to, I can try to post some drawings.

We want to build it in two stages, from one side wall to the ridge line, and then later add the other half (to spread out the cost and time). The first half of the barn will be for a small rabbitry, with double Dutch doors at one end and a pair of windows at the other end. Initially it will have a gravel or paving-stone (no mortar) floor (possibly with a concrete footing to keep out predators). The second half will be for equipment storage (tractor, etc.), with an 8' garage door at each end. Eventually we want to add an 8'-wide greenhouse along one side, and we also would like to finish out part of the loft for storage and for a sleeping room (for when DH is working nights). We plan to have wood siding and an asphalt roof.

We're thinking of using 4"x4" pressure-treated lumber for the main support posts, buried 2' into the ground. Would one post every 8' be enough for the two sides and the center (lengthwise)? How many posts should we use on the front and back (the gambrel ends), and how should we arrange them so as not to interfere with the garage doors or the human-entry doors?
 

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How tall? How many stories? 4x4's sound a little light. Frost depth and ground type will dictate depth for posts. I wouldn't go with an 8' door, much too narrow. What type of wood siding?, that will dictate how you frame. Why an asphalt roof?
 

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Haney Family Sawmill
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A gambrll barn is not conducive to building in stages. Your barn will be 16 feet to the peak in the center. When you stub it off two things happen one you have a profile that is 26 feet tall and 32 fet long, This is a wind deisaster waiting to happen. What you are describing is very conducive to a monitor design, Monitors can be built in thre stages with no trouble.
If you need a lumber list for either let me know.
 

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The last time I checked, a 2' footing was ok for your area but you should still go with a poured concrete footing with the posts attached to them with anchor brackets.
 

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I have an airplane hangar that had 4 x 4 posts used every two feet. It is in a wind protected area but we found out early on that 4 x 4's are too small for that here. It was an experimental building done by my father, and he thought that posts every 2' would be enough, considering they were in the ground 4' as well. Well, didn't work out that way. 4 x 4's are just too small and they want to lift out very easily. I would never do it again.

Jennifer
 

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Since you said a second story 4 X 4 is not enough... I am not sure a 6 X 6 would be enough.

I built a 40 X 16 barn 16 high and used 8 X 8s.

You didn't say how high you were planning on making the barn. That makes a difference.
 

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I would not just bury 4x4 posts even if they were big enough structurally unless I dug all the way down to the solid rock. Concrete footings with pads whose size will depend on the soil strength where the barn will stand are the way to go. If you want to save money on concrete calculate the weigh of the structure which will fall on each footing and adjust the size of pads accordingly.

It's much harder to fix foundation problems once the building is standing. And remember that anything attached to the structure in the future (loft with load of hay, etc.) will bear pressure on the posts too.
 

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I am about two thirds done finished with a gambrel roof shop. I built the bottom half first set the floor joists and sheathed the floor. that way I had a staging area to set the rafters for the side sheds as well as a place to walk while setting the trusses for the roof. If you want to build it in two stages that's how I would do it. I would use treated 6X6s four feet into the ground set in concrete for a pole barn eight feet on center is a stretch. I would go four feet on center so you can stagger the seams of your eight foot sheathing. Our shop is sitting on a steel reinforced concrete foundation with a concrete floor, the most expensive part of the project, but this thing is going to be around for a long time. Lumber prices tanked in our area so it was to our advantage to go stick built, we went with a metal roof the price between asphalt and steel was pretty much a wash. I wont have to re roof the shop in my life time and that is pretty much what I was looking for.
 

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I wouldn't trust what people post here for design ideas without the ability to tell what is good/bad/applicable information. Lets take an example: foundations.

There are many different foundation types you can use. Frost wall, floating slab, ring beam, cast concrete peer, post and pad. The most expensive is the frost wall. Its the full foundation below the frost line, with a concrete/block wall coming out of the ground.

The least expensive is the post and pad. You calculate the load on the building, and use concrete pads that can support it. Dig down below the frost line, or in your case the minimum wind withdrawl depth, place the pad, put the post on top of it, and backfill. The post needs some sort of withdrawl resistance. It can be nailed on 2x6's, rebar to dry concrete, or bolted connection to the pad. The posts also need to be rated for ground contact. You can't go to the local DIY store and pick them up. Probably a special order.

You need to know why people are making the suggestions they are. Cast concrete post with bolted posts? Do they have expansive soil (typical in Texas), termite problems, wet soils prone to rotting even treated lumber? Planning on limited life of the building/moving? Post and pad? Cheap, quick, maybe limite life?

Around here, Wisconsin, the cheapest building you can build is a post and pad, metal clad building. Rent a 18-24" auger, drill the holes, place the pads and posts, backfill. For taller buildings, they make spliced posts made of greentreated bottoms with untreated upper sections. After 12'-16' in length they get cheaper than solid posts, and have been shown to be just as strong as solid posts.

As just_sawing said, don't build a gambrel building one half of a side at a time. The trusses rely on both ends being secured. It can be done, but you have to have specially designed trusses, and take extra care in the center posts. You can build from one end to the half way point, but you need to add extra wind bracing, since the initial legth will be so short compared to its height.

Why do you want a gambrel roof with asphalt? Looks? Cost? Ease of construction?

If you are going to use a foudation anyway, I don't see a reason to make a pole barn. To me it makes sense to just build a stick built shed/garage/barn. You can get all sorts of plans, like this one for $109. The reason for a pole barn is the post foundation, metal walls/roof that don't need sheathing, speed of construction, freespan.

Do you have a budget? If you do, I would request a quote from someone like this web site. It'll get you started on the cost. (they have a 32x32 gabrel design) The good thing about the plan sets is that they have been engineered to a certain standard. You still need to see if the loads are adequate, but if they are, then the building should stand up to the design loads.

I don't know if you have anything similar to our local Menards. I know that they have a plan/design section in the store. On thier website they even have estimates on some of the buildings/plans. Heres a gambrel garage.

In short (way, way too late for that...) I'd say you need to look locally for more information, and look into predesigned plans sets. If you can't afford the plans, you can't afford to build the building.

Michael
 

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There's a couple of pole building books out there. Those will have examples you can rely on. The only other suggestion, I have is to consider CCA treated posts if you have any possibility of water around the post at the ground surface. The 2.5 lb/cf treatment is available. It's more available near coastal areas but I can order it in WV. I'm getting some for bridge decking. In non-salt water applications the marine grade CCA treated wood will last for generations even if rain water pools at the base.

These folks are located in NJ.

http://www.flwwood.com/products/pressure_treated_lumber.html#Marine Treated Lumber

The stuff I'm ordering will come out of MD. That plant can treat any dimension up to about 30' long. In other words if you want a 12"x12" 30' long they can provide it. I'm sure there's CCA treatment facilities serving the Gulf coast.
 

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I understand the need to build in stages.
Could you build half divided the other way? Either way you have 16 x 32. But a complete trussed roof line would be more suitable.
A gambrel roof truss is strong, but trying to build a half gambrel will take more material (expense).
Put all your posts in the ground for the whole building, so they'll settle the same, nail up the horizonal truss supports, set up trusses for the first half and sheet it. You can cover it with rolled roofing. Once you do the other half you can shingle the whole thing.

Give some thought to an attic truss instead of gambrel. That gives you the upper storage you want. Plus, if you want to expand, you'd be better able to add a shed style wing to one or both sides.
 
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