Designing a Mobile Shelter
(Photo courtesy of Deborah Moore)
The Pastured Flock
I have numerous times in these pages encouraged readers to keep their flocks on pasture if at all possible. There is no place a chicken (or duck or goose) is happier and healthier than foraging over good pasture, socializing and engaging in interesting natural behaviors, finding best-quality foods on her own, and enjoying the benefits of sunshine, fresh air, and exercise.
Unless your pastured flock is “anchored” on the main poultry house, you will need a pasture shelter to provide protection from rain and from predators, a place where they feel secure to roost at night, and (in the case of layers) nests for laying eggs. (You really don’t want to go hunting down eggs laid by laissez-faire hens.) Remember too the need for shade from the sun on the hottest days, assuming there is no tree cover in or on the edge of the pasture area.
Waterfowl usually show no interest in a shelter, even when it rains, but they badly need shade when it is hot.
Design of appropriate shelters is determined by many things—scale of operation, your skill set, materials already on hand, overall management choices, etc. Following are some design elements one might take into account while thinking through a pasture shelter construction project.
Easy Mobility
To avoid damage to pasture sod, it is necessary to move the shelter frequently, perhaps even daily. (How often depends mostly on stocking density, the point in the growing season, and whether the birds are confined to the shelter or are able to range.) Thus ease of moving the unit is a key design goal.
The larger shelters appropriate to small farms producing for markets are often moved by tractor or pickup. For most homesteaders, however, I would recommend avoiding moving with any sort of powered vehicle. Stay “up close and personal” with the move, to avoid injury to young or hapless birds that get in the way.
Attached wheels are not the only option for moving the shelter—rollers and sled-type runners are possible as well. Joel Salatin, innovator of the now-classic Polyface 10×12-ft mobile broiler pens, uses a two-wheeled dolly which he places under the trailing end of the shelter, then pulls from the other end. However, most homesteaders choose some sort of wheel, either permanent or temporary, for putting their shelters in motion.
Affixing Sabot
The size of the wheel is an important consideration. The smaller the wheel, the lower the trailing bottom rail, and the more likely it will catch on bumps or tussocks of grass on the pasture; or that a bird will get caught between ground and moving rail, and be injured. A larger wheel gives better clearance over uneven ground, and less chance of injuries to young or stupid birds, but is harder to take off and put on as a temporary wheel. Larger wheels (such as bicycle wheels) are more often used where they are permanently installed on the unit.
My own choice is to use an 8-inch wheel, the sort used on lawnmowers, widely available at garden centers or the local co-op. The hubs of the ones I use take a ½-inch axle, so I permanently install ½-inch bolts through the bottom rail on each side, front and rear. It is easy then to lift up each corner of the shelter in turn, popping the wheel on the bolt, then locking it in place temporarily with wing nuts. After the move, it is easy to back the wing nuts off and remove the wheels for use on other shelters.
With the smaller wheel I use, I do indeed find that the rear rail catches on bumps and tussocks, though such obstructions are usually no more than a brief annoyance.
For a pull, I use wire cable passed through a short length of old garden hose and twisted into a closed loop at each end. I hook the loops onto open hooks screwed into the lower rails of the unit, fore and aft. Since the hooks are open, I can use the one wire pull for moving all my shelters.
Weight
If you get even a quite heavy shelter up onto man’s oldest tool, the wheel, it will roll like a Cadillac. However, there comes a point where the weight of the unit makes it balky and even dangerous to work with, especially on uneven or sloped ground. Therefore, when thinking through your choice of materials or construction details, look for ways to shed weight to the extent possible, while retaining the strength your shelter will need to withstand rough use.
Perhaps the most important way to reduce weight while keeping and even increasing structural strength is the use of diagonal bracing. My first shelter designs featured all 2×4 construction with all right angles between the structural members—producing a frame that was unnecessarily heavy and clumsy to move, and not nearly as strong. Now, when constructing the bottom frame for the shelter, I typically rip 2x4s at 2-¼ inches and use those pieces for the bottom rails, and use the remaining 1-¼-inch thick pieces for diagonal bracing. The result is a tremendous gain in structural rigidity, with no increase in frame weight for the diagonal bracing.
Wind
A constant dilemma in shelter design: It is essential for mobility to make the shelter as lightweight as possible, and at the same time it is essential to add some sort of cover on at least part of the structure to cast shade and provide shelter against rain. In doing so, you’ve put up a sail with very little to anchor it down. How do you prevent your easily moved shelter from moving all too easily into the next county with the first bare-knuckle wind? There is an inherent trade-off between reducing weight while retaining structural integrity, and at the same time dealing with wind load. If you are an engineer, you can probably factor in aerodynamics as well—some shapes “catch the wind” more than others. I’m not an engineer, but it is obvious from designs I’ve used that the higher the profile, the more problem there will be with wind. (The classic Polyface broiler pen is 10×12 feet, but only 24 inches high.) Therefore I opt for squat and ugly rather than high and elegant. Also, I have found hoop-type structures and A-frames more wind-stable than rectangular, “boxy” profiles. And finally, the more cover attached to the shelter, the more it will act as a sail. Using poultry wire to replace the solid cover to the extent possible reduces wind resistance.
Whatever the profile and weight, however, any shelter that includes a solid cover and can be moved by hand will be blown away if the wind gets strong enough. Again we face a trade-off: The more we anchor the structure, the more hassle each move becomes (and the more tempted we become not to move the shelter as often as we should). I usually keep an eye on the weather reports, and anchor the shelters only when strong winds are predicted. I use “earth anchors,” stout steel rods with an abbreviated auger on one end and a closed eye on the other. It is easy to screw the auger end into the earth, anchoring the rod, then fasten the shelter to the anchor, using wire or cable around a bottom rail and through the closed-eye hook. Sometimes I use weights (such as buckets suspended from the shelter frame) to anchor the shelter against the wind.
Rectangular shelters often feature a hinged “lid” on top for access to the interior. A lid should be fitted with a stout, positive-lock latch. The country version: putting a both-hands rock on top of the lid after closing it.
Whether to Install a Floor
A major question in the design of the shelter is whether to install a floor. The classic Polyface broiler pen is floorless—the whole point is to give birds confined to a pen constant access to pasture. In management strategies in which the birds are not confined to the shelter (as when the flock roosts in the shelter at night but ranges inside an electric net during the day), the addition of a floor to the shelter might make sense. (More below.) If you do add a floor, however, I strongly recommend either wire or plastic mesh. A plywood or other solid floor quickly accumulates a layer of caked droppings that is unpleasant, unsanitary, and especially hard to clean in the cramped quarters of a shelter.
Avoiding Injuries
All birds are young to begin, while some adults seem just plain stupid. Both classes will sometimes get a leg caught under the trailing rail of a shelter being moved, and be squashed between the rail and the ground. Great care should be used, therefore, not to move the unit too fast, and to be constantly vigilant to the birds inside the shelter. Any hint of distress calls for an immediate halt. It is best to enclose the end you pull from with poultry wire (rather than solid cover), so the back rail is visible as you pull. A helpful strategy is to move the shelter when you feed: Place the feeders outside the shelter and get everybody crowded eagerly around them, then shut the door to the shelter and roll away.
Another strategy for avoiding moving injuries is the addition of a floor. The shelter can be moved early in the morning, while the birds are still shut inside, and released to the outside only after the move is complete.
In the Garden
A pasture shelter of the right dimensions is a great adjunct to gardening. My garden beds are 42 inches wide, so I made one of my shelters 4×10 ft. I can park the shelter on a bed and allow the birds to work a 10-ft patch at a time, while keeping the other beds off limits. Great way to till in heavy weeds or cover crop, and make way for planting.
Doors
I use one small A-frame completely open at each end, but for most shelters I like to have a door. Even if I don’t close it routinely, I want the option of closing the birds in (to get ready for a move from one netted area into another, to do a census or selection, or in preparation for slaughter).
Nests
If the shelter is serving layers, it should have nests—simply mounted on the framing is best—which should be accessible from the outside. I’d be embarrassed for you to know how many years I clambered inside my large A-frame to collect eggs before that Duh! moment. It was easy enough to hinge a scrap of plywood for an access door and protection from weather, but it would have been easier to make this provision from the first.
All-Season?
An important design question is whether the shelter will serve the flock in summer only, or whether it will give climate-adequate protection in the winter. Maintaining the shelter’s weight at the mobile end of the spectrum and still provide a sufficient bulwark against winter’s extremes can be challenging.
Predation Issues
A shelter on its own is subject to digging attack if floorless. Dogs and fox are diggers, as are other predators. In a free-standing shelter, a 2×4 mesh welded wire floor is the minimum required to defeat diggers. (Such a floor also has the virtue of letting birds graze through it during the day.)
I keep all my shelters inside electronet, so use nothing but floorless shelters. And I don’t shut up at night—the sleeping birds are safe enough behind an electric perimeter. If you are neighbors to owls, it would be advisable to shut the shelter doors at night.
Be aware that poultry netting may not be impervious to unexpectedly powerful (and determined) predators such as dog or raccoon. I’ve had both rip through poultry netting with tooth or paw. (Bet you can’t do that). If you are exposed to predators this potent, you might use ½-inch hardware cloth, well secured, in lieu of ordinary poultry wire.
Another option is to “wire for defense.” After the attacks (in a Salatin-style 10×12 broiler pen) referred to above, I ran a couple of passes of single-strand electric wire around the shelter, standing it off from the structure with plastic or porcelain insulators. With completely satisfactory results.
Watering Issues
In the case of shelters that confine their birds, most folks prefer a hanging waterer that can be filled from outside, as opposed to lifting heavy waterers in and out. My birds are not so confined, so I run supply hoses—which Y-off as needed—from household pressure out to automated (float-operated) waterers on the pasture.
If you have the misfortune to be raising a crop of Cornish Cross, I’d advise placing a waterer inside the shelter, whether its door is open or not. I once lost 22 Cornish Cross just at the age of slaughter: An out-of-season May heat wave hit, and the poor dorks sat in the shelter’s shade on their butts and died rather than walking 10 feet for a drink of water.
Roosts
Chickens do not absolutely have to have roosts. However, they have a strong instinct to roost, and will be more content if enabled to do so. (And remember that little feral wildcard: If denied the opportunity to roost, chickens may go roost in the trees. Just imagine where that might lead.)
In a pasture shelter, have all brace framing possible do double duty as roosts. For instance, if you are constructing a fair-sized A-frame, you will certainly want to add collar ties. Space them low enough under the peak to accommodate several sleeping birds.
Materials
Pasture shelters have been based on every material other than titanium—you will doubtless make yours from a material you are comfortable working with. For me, that material has always been wood. (The one exception was a 10×10 hoop shelter based on ½-inch solid fiberglass rods.) It is heavier than some alternatives (which up to a point can be an advantage), but joins easily and takes screws and staples for putting on cover, wire, or hinges. I strongly recommend screws for securing wood—unlike nails, they will not work loose in a structure that will be yanked and wrenched a good deal. However, I do not use ordinary wood screws (requiring drilling of pilot holes)—a self-drilling screw such as a deck screw or the like (if galvanized against the weather) holds well and is easy to set without drilling pilot holes.
If in prolonged contact with the ground, wood will rot if not sealed regularly, and placed up on blocks over the winter. You may even want to set each corner on a small block each time you park the shelter. Since the bottom rails are more subject to rotting out than any other part of the frame, you might do well to design a frame in which the rails are independent of the rest of the frame and covering, and thus more easily replaced separately.
A popular option is the hoop shelter made from heavy gauge welded wire livestock panels, bent from one edge of a frame and secured to the other in a semi-cylinder. Doors and wire netting can be added to the ends using light wood framing. Countless designs have been based on PVC pipe. I don’t work with PVC much, so I’ve never used it. I’ve seen pictures and descriptions of use of PVC in cases where results were satisfactory. All of them, however, were based on heavy-duty PVC, something like Schedule 40. All the PVC structures I ever saw put together from lighter PVC—one-inch pipe and the like—turned out to be disasters: not only blown away but irretrievably wrecked in the first no-nonsense wind.
If light PVC is a bad choice, 1-inch PVC pipe frames covered by plastic tarps are the absolute worst. They weigh nothing and are flimsy—hello wind! But actually, it’s a mistake to use plastic tarps in any pasture shelter: They shred all too quickly from ultraviolet exposure, wind, and flying claws landing on them.
So what is the covering of choice as a rain and sun barrier? I’ve seen shelters sided and roofed in plywood. Unless quite small, such shelters are incredibly heavy, the kind of thing you move only once or twice a year when you have friends around and some beer to share. However, such shelters are more likely to be winter-proof than most other designs.
Sheet metal roofing is a good choice. Galvanized or baked-on-paint steel roofing is cheaper and heavier. Aluminum roofing is lighter but more expensive. Either will last a long time.
An alternative is 12-mil or 24-mil woven poly fabric. This is a greenhouse plastic available from any greenhouse supply, but usually in 100-foot rolls. I know of only one source for these fabrics custom-cut to your order: Greenhouse Sales in Neche, North Dakota. (204-327-5540) (Northern Greenhouse Sales) They sell a 12-mil woven poly, black on one side and silver on the other (giving the option of installing for solar gain or reflection). More durable will be the 24-mil. There is no silver/black version, but there is white/silver or white/white. Either white or silver reflects solar heat away from the structure (the white is likely to be a little more effective than the silver at keeping the interior cooler), while the white on the inside makes for more interior light. These tough woven fabrics last longer than any other version of plastic I know of. The 24-mil cover on my big A-frame survived a tumble through 30 feet of underbrush under the lash of the wind—without a tear. As Andy Lee, author of Chicken Tractor, characterized it to me, it’s “bulletproof.”
