Thank you! It's working out really well! Ours is 12ft by 30ft roughly. We used treated 2 by 6 boards for the bottoms with fencing plates to connect them. The PVC is 3/4 inch conduit schedule 40. We used 2 10 ft pieces for each half circle. The poly is 11 mil custom ordered from Northern Greenhouse. The poly was by far the most expensive of the whole thing. I believe around $330 for 22 ft by 32 ft but well worth it! It is heavier than a tarp but woven like a tarp. We attached with wood lathe and nails at the bottom of the perimeter. We used very cheap plastic on the end walls because I forgot to order them from Northern Greenhouse but will get it for next year. The plan is to take the poly off once the final frost happens in Spring and then add shade cloth to put over the future vegetable garden that will be planted right in the deep bedding. We are concerned with animals trying to get into the coop, so we will add an electric wire or 2 around the perimeter and hope that deters. We have small basement vents at the top of the coop right now. We are working on the ventilation aspect. The coop isn't air tight but definitely draft free. We will add more vents to the top of the end walls as needed! We are having rather high temps for December (65s) and is does get moist in the coop but at night the moisture moves out. We also aren't at freezing temps at night yet but I am watching for frostbite.
Everything to build the coop was purchased at Home Depot except the poly, which was from Northern Greenhouse (google them). We leveled the perimeter before we did anything and then attached each side of the PVC. We pulled the two pieces together and connected at the top. We also ran PVC through the top and you could add a rib on each side for higher winded areas. We attached those by drilling through both and putting a carriage bolt with a nut on the end through both pieces. We haven't anchored the coop to the ground and I don't know that we will need to. We had some high winds over the last week and it doesn't move. But we may find that to be needed after all!
I did NOT level the perimeter of my coop, and while the base is secured to the ground, there are gaps here and there under the 2x4's where they warp or my dog or chickens have dug. Air gets in, as well as the little birds, and sometimes it seems more like an aviary than a chicken coop. The plywood ends are done in pieces, and there are seams that expand and contract with the humidity changes. The first day after we put the too-small tarp on - there was a gap of 12" along the bottom of the tarp and the 2x4 to which it was attached - we had a drop in the barometer, and a high wind filled the coop with air and lifted the tarp right off. Right away we fixed the gap with the strips of plywood, and I cut the windows in one end to let the air exit should the coop ever try to puff up again.
Using plywood to extend the sides up a bit might be a good idea. It can give you more options for choosing sizes of standard sized tarps, and the tarp is easily attached to it; AND you can drill holes or add vents for ventilation close to the bottom. Too bad my tarp had to blow off for me to find this out. Plus, I am thinking it will help in setting up a garden in the coop next spring when I free the chickens. I think these coops have a lot of possibility, and I am excited about them.
After thoughts and considerations:
Fastening the tarps to a hoop frame so that there were no gaps or loose edges is essential; it was a challenge for me with these high tunnel structures. The plastic tarp clamps popped off and they seem to get brittle in temperature extremes. Fastening the tarp with lathe and nails is a good idea, and I probably should have done this with my smaller unfinished vinyl tarp, but my poly tarp has grommets and I'm reluctant to put holes in it; so I just screwed through the grommets with sheet metal screws and washers. Ball bungees are probably better, though, and I will probably upgrade to those. Also plan to add more grommets, maybe so they're spaced at 12". All this to avoid the high price of a custom cut expensive covering!
Whenever air can enter the coop, it is essential that provision be made for its exit. Condensation and ventilation are concerns.
Without a frame or rigid support for the ends, the hoops can twist and distort in high winds, especially if the smaller conduit is used.
I am considering incorporating some of the translucent corrugated panels into the plywood ends. We will see.
As you did, FlippingHills, I assembled my hoop frame before bending it and connecting it to the 2x bottom perimeter. It is MUCH easier to fasten the "beam" to the conduit before before the structure is in place. It may be worth considering putting in some upright supports if snow load is heavy and/or the coop seems to sag. I am watching for this in my 15' long coop, but it seems to shed snow rather well, so far.
I am thinking I will leave the poly in place so as to extend the short growing season here. Maybe put shade netting over all in our hot summers.
Well, this has been another long post. Winter housing like yours is so desirable, buildable, and affordable I can't imagine anyone not wanting to have one. They come with special concerns, though, ESPECIALLY in high wind areas and where snow loads and humidity are issues. Am hoping to start some sort of dialogue where people can learn from my experience (and mistakes) and explore what's possible with these coops.
So I'm wondering what I have to do to keep my coop from racking end to end? Do I have to mount it to some sort of heavy post at the ends if I don't want guy wires to trip over, or what? I AM going to research this, and Google Northern Greenhouse. Thanks again for all the details and ideas.