How to predator proof the open floor of The Garden Ark mobile chicken coop

How to close floor of chicken tractor coop

I’ve been working for some time on a solution to predator-proof the open floor of The Garden Ark mobile chicken tractor. The challenge has been finding a way to secure the floor without closing it off completely or permanently. After all, you need the open floor for mobility, cleaning, and access to grazing. After much trial, I finally came up with an elegant solution (essentially a version of one of these turned upside down) then put it to the test. It works perfectly, and now I’m excited to share it. 

Why cap off the bottom of The Garden Ark chicken coop?

The Garden Ark chicken tractor is an open-floored mobile chicken coop, perfect for housing a small flock of backyard hens. The open floor has lots of advantages, the main one being that your flock can graze directly on grass and veggies or scratch around in the soil. You can move the coop from spot to spot in your garden, and the chickens will scratch, till, and add fertilizer wherever they go.

The one drawback to an open-floored coop is that a digging predator could, with some determination, tunnel its way into the enclosed part of the run. This doesn’t happen often — in fact, I have yet to hear of it happening from anyone who has built The Garden Ark and left the bottom open —  but if you’re in a predator-prone area, prevention means peace of mind.

Chicken coop after an attack by a neighborhood dog
Brooke’s Garden Ark was attacked by her neighbor’s dog. The animal was determined enough to chew and scratch at her coop so ferociously that he left traces of his own blood behind. Had this or another predator put that same energy towards digging, they might just have been able to enter the coop from below. In the end, Brooke’s chickens were unharmed, and her neighbor eventually agreed to pay for repairs. Gotta love small claims court.

Look, I’m not trying to scare you into thinking you have to cap the bottom of your mobile coop at all times. This might just be something you want to do when you’re gonna be away for a few days or if you know you have a specific issue with tunneling predators.

By building this simple “bottom cap” and setting your Garden Ark on top, you can park your chickens in complete safety. The cap bars entry from below when the coop is placed on top of it, yet unlike attaching wire mesh directly to the bottom of your coop, it detaches quickly and easily so you can clean out bedding and move the coop. Of course, there are other ways to secure the open floor, such as rolling your coop onto a paved surface or onto a “pad” of hardware cloth staked over the ground. You should do what works for you.

Don’t have The Garden Ark? With some adaptation, this same idea should work for any open-bottom chicken tractor. You basically want to build a frame to match the dimensions of your coop’s footprint.

A few notes before getting started with the project

Assess your skill level. If you’ve used our coop plans to build your backyard chicken coop, this project should be very easy.

Time. About 30 minutes? Let me know in the comments.

Measurements. Maybe you altered the footprint of your The Garden Ark when building it, or maybe you have another chicken coop design altogether. Feel free to modify the measurements to meet your needs and coop. Metric units appear in green.

Safety. Read our disclaimer. Follow all manufacturers’ instructions when using tools, materials, or equipment. Protect your eyes, ears, and limbs. Build safe, and have fun!

Plans for a predator-proof bottom cap for The Garden Ark mobile chicken coop

Free plans for mobile chicken coop floor protection

Materials List (to build one 5′ x 3′ bottom cap – 1525 x 865 mm)

  • 2  8-foot (2400 mm) two-by-fours or two-by-sixes. Note: The wood will be in direct contact with the ground, so either choose a naturally rot-resistant species like cedar or redwood or use a cheaper softwood (spruce, pine, fir) and seal it well or preserve it with a garden-safe product like Timber Pro UV Internal Wood Stabilizer.
  • About a 2- or 4-foot length (600 mm) of a two-by-two. You could use a two-by-four instead. See note above about protecting the wood.
  • 59″ (1500 mm) length of 3′ wide (914 mm), 1/2 in. (13 x 13 mm) galvanized hardware cloth, also known as “welded wire mesh”
  • About twelve (12)  3″ (75 mm) exterior screws
  • About four (4)  2  1/2″ (64 mm) exterior screws
  • About seventy (70)  3/4″ (20 mm) galvanized poultry net staples

Tools List

  • Circular saw or handsaw
  • Couple of sawhorses
  • Power driver/drill
  • Hammer
  • Tape measurer
  • Pencil


Cut each of 2 two-by-fours or two-by-sixes into a 60″ (1525 mm) piece and a 34″ (865 mm) piece. These will make up the outer edges of the bottom cap frame (see diagram below). Note: if you adjusted slightly the measurements on the skids of your ark to account for the milled dimensions of the lumber you used, make those same adjustments here. You simply want the outer dimensions of the bottom cap frame to match those of the skids on your ark.

Cut the two-by-two into two 5″ (125 mm) pieces — 7″ (175 mm) if you’re using two-by-sixes. These will be the corner pieces, which will stick up about 1  1/2″  (40 mm) above the height of the frame to “lock” the base of The Garden Ark in place. You only need two at opposite corners to accomplish this. If you prefer one in each corner, cut four pieces.

Lightly sand the cut pieces and paint, seal, or treat them as needed with a non-toxic wood preservative like Internal Wood Stabilizer. Follow the manufacturer’s instructions for any product you apply and allow the proper time to cure before exposing the wood to moisture.

Easy plans for raised vegetable bed for mobile chicken coop.

Attach the two-by-four or two-by-six pieces together to form the outer edges of the frame, using 3″ (75 mm) exterior screws, two or three per joint. Refer to the photo for placement. You will probably want to pre-drill the holes to prevent splitting.

Frame to wire floor of chicken coop

Attach the hardware cloth to the bottom using 3/4″ poultry fencing staples, every 3-4 inches.

Attach wire to bottom of chicken coop frame

Attach wire to secure the floor of a mobile chicken coop

Flip the frame and attach the two-by-two corner pieces in opposite corners using a couple of 2  1/2″ (64 mm) screws for each and drilling pilot holes to prevent splitting. You want about 1.5″ of each piece to stick up above the top edge of the frame. Drive the screws through the two-by-two and into one of the two-by-fours or two-by-sixes. Notice the direction of the grain in the wood and try to sandwich the grain with your screws. This reduces the chance of splitting.

Corner pieces on Garden Ark bottom frame
Fill this base frame with some soil or bedding — then simply set your Garden Ark on top! Your hens are now fully secured in both the run and henhouse areas, so there’s no need for nightly closing of the sliding door. You can attach the ark to the base with some latch hardware if you like, but the weight of it should hold it down quite well. You just don’t want to screw the ark to the base frame because you’ll want to be able to separate the two easily for cleaning and mobility.

Predator proof the open floor of chicken coop tractor

I hope you’ve found this tutorial helpful. If you want to learn how to build your own Garden Ark mobile coop, check out our chicken coop plans, available in both U.S. standard/imperial units and metric units. A hardware Quick Kit is also available (U.S. only).

You might also like our free plans for grazing frames for chickens and our free plans for a raised vegetable garden bed for your chicken coop, both of which will help you keep your chickens in the green.

Unlike with the coop plans, I do not offer email support for this free bottom cap plan. But if you have any questions, comments, success stories, or tips on how to incorporate your backyard chickens into your raised bed vegetable garden, please leave a comment below, and I’ll do my best to respond.

Finally, subscribe to Coop Thoughts. You’ll get notice of the latest posts as they happen. It’s free, ad-free, and you can unsubscribe at any time. Click here to add your name to the list. You can also follow The Garden Coop on either Facebook or Google+. Thanks!

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