Building a Mobile Shelter
Thinking Through the Design
In “Designing a Mobile Shelter” and other articles in the “Ranging the Flock” section, I discuss the principles to consider when designing a pasture shelter for poultry; and share photographs representing the many approaches poultry people have made to this project. This article describes step-by-step construction of a serviceable shelter that should be adequate for most backyard flocks. It includes a nest box and plenty of roosts, so would work well with adult laying flocks. However, it could also be used to raise young birds on pasture. This particular model is floorless, but a floor of wire or plastic mesh could easily be added if desired.
I like the A-frame structure for a shelter, which provides more structural integrity for less weight, and is more stable in the wind, than more boxy designs. When planning my new shelter, therefore, I decided in many ways to duplicate my most successful design from the past, with a few modifications learned through experience.
The biggest change from my previous design is the choice of metal roofing to cover it, in lieu of woven poly fabric. Since reading the article “Polymers Are Forever” (Orion magazine, May/June 2007), I have tried to cut out the use of plastics wherever I can. It is disturbing to realize that the plastic which we use with such convenience today will most likely still be somewhere on the planet in the time of our great-great-great-grandchildren. Still, the woven poly fabrics may be the best choice for some. As said in “Designing a Mobile Shelter”, it is much lighter than metal roofing. (The metal roofing on my new A-frame added about 80 pounds to the shelter. A piece of 24-mil woven poly, custom cut to cover this same shelter, would weigh about 10 pounds.) Of course, up to a point, the added weight can be an advantage: There is no doubt that my new, heavier shelter is more stable in the wind. Cost might also be a factor when deciding between these two coverings: I spent $112 for the metal roofing for my new shelter (including a piece of ridge vent to cap it), a piece of 24-mil white/silver woven poly sized to fit this structure would have cost $78. A final consideration is durability: My previous A-frame with a 24-mil woven poly cover is still going strong. Based on current degree of degrading from weathering, I would estimate a total service life of twelve to fifteen years. The galvanized steel roofing with baked-on enamel paint which I used (Fabral’s Grandrib 3) comes with a 25-year warranty, so I expect total service life to be considerably more than that. (One could of course choose plain galvanized roofing, but the savings realized would not cover the cost of painting it more than a couple of times.)
Another change I was glad to make: In the past, I have used 8-inch wheels on my pasture shelters, with the .½-inch bolts that serve as the wheels’ axles set in the exact center of the bottom rails. This configuration results in a very narrow gap between the ground and the rear rail, which as a result tends to catch on every bump or tussock when I move the shelter. For the new shelter, I bought a set of 10-inch wheels. Instead of drilling through the center of the rail for the axle bolt, I offset the hole toward the bottom of the rail by an inch. The combination of the greater wheel radius and the lower axle hole gives me an additional two inches of clearance when moving the shelter. Based on your own particular needs, you may prefer a smaller clearance (to prevent escape of birds from inside while moving, for example), but I love the way my new Chicken Ferrari rolls across the pasture.
The following report is intended to give you, the reader and pastured poultry keeper, a solid introduction to the construction of a proven shelter design. There are endless modifications you could make to better serve your own needs and circumstances.
- 6 – 6-ft sheets of Fabral’s Grandrib 3 painted steel roofing
- 1 – 10-ft 6-in Fabral’s ridge vent
- Fabral’s painted screws with neoprene washers (optional) or a box of neoprene washers
- 4 – 12-ft construction grade 2x4s
- 6 – 10-ft 2x4s
- 4 – 8-ft 2x4s
- Assorted deck screws (See note.)
- 4 to 8 metal corner braces (See note.)
- 4 – .½-in carriage bolts, 5 inches long
- 4 each flat washers, lock washers, and hexagonal nuts for the carriage bolts
- 4 wing nuts for the carriage bolts
- 4 wheels with .½-inch axle bores
- 1 10-ft roll 1-inch mesh poultry wire, 48 inches wide
- Small fence staples (for poultry wire)
- 2 pairs 1-.½-inch utility hinges
- 1 – 1-.½-inch barrel bolt
- 4 – 4-.½-inch open screw hooks (â€œceiling hooksâ€)
- 1 sheet .½-inch CDX plywood (optional)
- Small roll of .¼-inch hardware cloth (optional)
- 1 quart or so wood sealer
- A short length of twisted wire cable and a scrap of old garden hose
Notes on Materials
(1) I ordered the metal roofing through my local farm co-op, custom cut to my order. There are other options for metal roofing than Fabral’s Grandrib 3, of course. Check out the possibilities with your local farm supply. The width of coverage of the Grandrib 3 is 36 inches, so the choice of three pieces per side dictated a total length for the shelter of nine feet. As for the length of the roofing pieces: I used the Pythagorean theorem to calculate the 6-ft length, based on a bottom rail of 8 ft 3 in, and on a preference for cutting angles on the ends of the rafters at 45 degrees. If you are making a smaller or larger shelter, or prefer a different profile with reference to its height, use the good old Pythagorean theorem to recalculate the length of your rafters (the hypotenuse of a right triangle) and the angles at which to cut the ends of your rafters.
(2) For fastening Grandrib 3 onto roof framing, Fabral offers a hex-head painted screw complete with neoprene washer. Since I had some left over from a larger roofing project, that is what I used. They are quite expensive, however, up to 16 cents per screw. You could use decking screws for this part of the job as well, adding small neoprene washers to seal the screw holes from the rain.
(3) For the framing, I bought all 2x4s and ripped them down as needed. You could of course buy lumber already cut to your needed dimensions (2×2, 1×2, etc.) if you prefer.
(4) Do not use nails for a pasture shelter, they will work loose as the shelter is jerked about in moving. A coarse-thread deck screw, galvanized or coated against weather, will provide much more durable framing joints, and will not require the drilling of pilot holes (except at the ends of pieces to be joined). I keep a supply of a wide variety of lengths and shank sizes on hand at all times. For this project, I used, as appropriate to the join being made, all of the following: #7, 1 and 1-5/8 inches; #8, 1-.¼, 2, 2-.½, and 3 inches; #10, 3-.½ inches.
(5) I had a number of 3-.½x.¾-inch steel corner braces (“corner irons”) on hand, so I used two on each corner. If you can get larger corner braces, you should need only one per corner.
(6) If you have some scrap wood on hand, use it to assemble a nest box. If you do not, you might find it easiest to make one from plywood. If you buy a sheet of plywood, you should have at least half the sheet left over after making your nest box.
(7) I always use .¼-inch hardware cloth (welded wire mesh) for nest bottoms that are more “self-cleaning” than solid bottoms, so I had on hand the small piece required to floor the nest box in this shelter. If you can’t find a source that will custom cut to your length, you will probably have to buy a 10-ft roll and keep the remainder on hand for other projects.
(8) The size wheel you want to use on your shelter is up to you. For most pasture shelters, you want a solid (non-pneumatic) wheel, available from a garden or tractor supply. See discussion of wheel size above.
(9) The sealer I used was Cabot Waterproofing, a clear silicone sealer for wood. I didn’t coat the interior parts of the frame that will be completely sheltered from blowing rain. I applied several liberal applications, however, to the bottom rails and end framing, and the end grain of stringers and rafters. I used about two quarts of sealer.
(1) Set rip fence of table saw or hand-held power saw to 1-.¾ inches, and rip all four of the 12-ft 2x4s in half. Cut each of the resulting pieces in half cross-wise, that is, into 6-ft lengths. Reserve 14 of these pieces for the rafters of the shelter, and set aside the other two for other uses.
(2) Cut 12 inches off four of the 10-ft 2x4s, to yield four 9-ft 2x4s. Set aside two of these 2x4s to use for the side rails. With rip fence still set at 1-.¾ inches, rip the other two 9-ft 2x4s in half. Set aside the resulting four 9-ft pieces, for use as stringers.
(3) With the rip fence still set to 1-.¾, rip one more 10-ft 2×4 in half and set aside for use as collar ties and end framing.
(4) Re-set the rip fence to 2-.¼ inches and rip the last 10-ft 2×4. Set aside the 1-.¼-in thick piece for later use. Cut the 2-.¼-in piece to 9 ft, for use as the ridge pole.
(5) Assemble the bottom rails. [Please note that in “Designing a Mobile Shelter”, I said that it is possible to cut down on weight by ripping the bottom rails at 2-.¼ inches, which normally is plenty heavy for a shelter with adequate cross bracing. In the present case, however, I was adding a lot of weight because of the choice of the metal roofing as cover. Therefore, I used full 2x4s for the bottom rails.] Lay out the bottom frame, with the two 9-ft 2x4s previously cut (Step 2) to the outside, and two of the 8-ft 2x4s to the inside. Study the photo of this step carefully and make sure that the 9-ft rails set the length of the bottom frame at exactly 9 feet; while the 8-ft 2x4s, set on the inside of the outer rails, make for a width that is 8 ft, 3 inches (8 ft plus the thickness of one nominal 2×4 times two). We doubled up on our smaller corner braces, and used #10×3-.½-inch screws for drilling into end grain, and #7×1-5/8 screws when screwing into cross grain. (#8×1-5/8 would have been even better.) Note that as we begin assembling the frame, we want to be as square as we possibly can. If you have a large enough completely flat surface (such as a garage floor) to work on, that is the best choice. That was not an option for us, so I simply used the most level section of lawn I have (well, the most level that remained in the shade most of the time). For squaring up the corners, I laid each of the corners in turn on a sheet of plywood when joining them with the corner braces. Square your corners as well as you can (measure on the diagonal from opposite corners, the two measurements should be the same if the frame is square) before the next steps, which will be “locking in” the structure.
(6) Cut 45-degree angles on both ends of the 14 rafters. Be careful with this step: You want to end with rafters that still measure a full 6 ft on the top edge, with the angles coming in from the ends. Be sure you’re clear on this point by studying the photos of the attachment of rafters to ridge pole and bottom rails. When driving screws into the ends of the rafters (or near the ends of other pieces elsewhere in the construction), I first drill a pilot hole to prevent splitting the end. (When driving deck screws into the middle of the work piece, no pilot hole is necessary.)
(7) I hope you have a buddy willing to help set the first two pairs of rafters, doing that single-handedly would be more challenging than juggling five balls while walking a tightrope. Screw the ends of all the rafter pieces solidly onto the ridge pole and the side rails, setting the rafters at 18 inches on center. [Note: Be aware that some roofing materials might require a different spacing of the rafters.]
(8) Attach two of the 9-ft stringers cut in Step 2 to connect the rear and the front rails. I came in 32 inches from the right and left ends of the front and rear rails to set the stringers. You could vary that distance, depending on the size door (and access to the nest box in the rear) you prefer.
(9) Re-set rip fence to .¾-inch. Rip the two remaining 8-ft 2x4s to give eight pieces .¾x1-.½ inches. (No, they’re not all precisely .¾ inch thick, but we don’t want to go crazy figuring the kerf here.) Set aside four of these pieces for later use. Check a final time that the bottom frame is square. Trim the remaining four pieces to make diagonal cross braces, from each lower corner up to the top in the middle of the structure, attaching to the undersides of the rafters wherever they cross. Though fairly lightweight, these cross braces add tremendously to structural rigidity.
(10) Using the 1-.½x1-.¾-inch stock cut in Steps 1 and 3, cut pieces to frame for a door and access to the nest box on the ends. (Study the photos for the general layout. You’ll have to do a bit of trial-and-error to establish the correct angles.)
(11) Using the same 1-.½x1-.¾-inch stock, cut five additional pieces to use as collar ties, which join opposite pairs of rafters. The collar ties add to structural integrity, but they can serve double duty as roosts for your birds. Exactly where you set them is up to you: The lower you set them, the longer they are and the more useful as roosts; the higher, the easier it is to get around inside the structure when you need to do so. A good compromise for us (based also on best use of the pre-cut stock used in this step) was to make the collar ties 29 inches long (measured across the bottom side), which set the top 13-.½ inches from the ridge pole.
(12) To complete the framing, we installed an additional two stringers (16 inches up from the first pair) connecting the uprights in the framing at the two ends (using the remaining two 9-ft pieces cut in Step 2). These two stringers are not essential structurally, but we wanted them to provide a comfortable amount of roosting space for the birds. Remember the 1-.¼x1-.½ stock cut in Step 4? We cut pieces from that to make two center supports for the pairs of stringers on each side. (See photo.)
(13) At this point we have a frame that is rock solid. I’m going to leave it to you to design your own nest box and end door if you want them. (I rarely use a door, since I use electronet to protect the flock, but always want the option of shutting in the birds, for a census or selection or whatever.) For these two projects I used the 3/-4 inch stock generated in Step 9 and the remaining 1-.¼-inch stock from Step 4, plus (for the nest and its hinged access door) some scrap .½-inch CDX plywood. I used some .¼-inch hardware cloth on hand for the bottom of the nest box. I used more scrap plywood to give additional protection to the ends of the nest box from blowing rain. (See photo.)
(14) While all parts of the frame are still accessible, coat all surfaces that could possibly be reached by blowing rain with a good wood sealer. Don’t forget the bottoms of structural pieces, with a structure this rigid, there is no problem flipping it on its side to get to any surface needing application.
(15) Cut the 1-inch mesh poultry wire for the (mostly triangular) spaces to be sealed off in the front and rear. Staple into place. Staple some over the door frame as well. (You’ll see in the photo that I used a convenient piece of .¼-inch hardware cloth instead.)
(16) We attached the metal roofing, using four screws per rafter. The Grandrib 3 we were using is designed to be laid down over horizontal roof purlins, but the addition of purlins is not needed in this simple structure. Therefore, we simply attached the screws into the rafters themselves, occasionally doing so through a ridge in the Grandrib 3 (not recommended when installing on a house roof, for example), but mostly through a flat section of the profile as recommended. We then attached a ridge vent over the top to protect the interior from rain. If you are using the 24-mil woven poly to cover your shelter, you can order a plastic lath called â€œcinchstrapâ€ for nailing down the poly.
(17) Drill .½-inch holes into the side rails, front and rear. I drilled mine with the center ten inches in from the end, and one inch up from the bottom. Insert the .½-inch carriage bolts through the holes, from the inside of the rails. Place a flat washer, then a lock washer, then a hexagonal nut on the bolt, and tighten until the square â€œshouldersâ€ of the carriage bolts are firmly engaged in the wood. Now simply pop the wheels on the bolts and lock them down with wing nuts. (If installing permanently, use more hexagonal nuts. The wingnuts make it convenient to put the wheels on and off with ease.)
(18) Drill pilot holes and then screw in the four open hooks into the front and back rails. Make a pull using a length of wire cable, twisted into a strong loop at each end, and a scrap of old garden hose as padding for your hand. Loop the ends into the hooks and pull to move the shelter. Now you’re rolling!