Bird flu showed up in two backyard flocks in Northern California this month. About 40 birds in a Sacramento County flock were confirmed positive on October 5, and about 50 birds in a Solano County flock on October 20, according to USDA figures reported by CBS Sacramento.
The timing isn't a surprise. The USDA's Defend the Flock program says wild birds migrate in the spring and fall, and that raises the risk for backyard birds. One of its basic steps is to use covered enclosures or netting to reduce contact with wild birds.
That's where we come in. A coop's job is to keep wild birds, rodents, and predators on the outside, and that comes down to which mesh you put where. Here's the short version, then the details.
The Short Version
- Chicken wire keeps chickens in. It was never meant to keep anything out.
- 1/2 inch hardware cloth goes on the coop and on every wall of the run.
- 1/4 inch hardware cloth goes low on the coop, where mice and rats come in, and anywhere chicks live.
- Cover the run. A solid roof is best. Mesh with a tarp over it is next.
- Bury an apron so nothing digs under the wall.
Chicken Wire Is Named for What It Keeps In
Chicken wire, also sold as poultry netting, is light wire twisted into hexagons, usually 1 or 2 inches across. It's cheap, it bends easily, and it does exactly what the name says. It keeps chickens from wandering off.
Keeping predators out is a different job. A backyard flock guide from University of California Cooperative Extension and CDFA says not to use chicken wire for your coop, because it's too weak to keep predators out. A UC Davis coop design guide sets the bar at nothing less strong than hardware cloth on the coop itself, and notes that even small predators can rip through chicken wire.
The size of the hole matters as much as the strength. Raccoons don't have to break in to do damage. Ohio State's extension fact sheet on predators of poultry describes raccoons reaching through the openings of mesh pens and grabbing birds that sit too close to the wire. A 1 or 2 inch hexagon leaves plenty of room for that.
Why Hardware Cloth Works
Most hardware cloth is steel wire welded into a square grid and galvanized. Two things make it the right material for a coop.
- Every crossing is welded. There's no twist for an animal to pull apart.
- The openings are small. Our 1/2 inch hardware cloth is 2 mesh in 19 gauge wire, with a clear opening of about 0.459 inch. UC's pest management program uses 1/2 inch wire mesh on the back of a raccoon trap for exactly this reason, so the raccoon can't reach in from outside.
UC's backyard flock guidance from this year says the same thing in one line: put hardware cloth with 1/4 to 1/2 inch mesh on all openings to keep out small birds, rodents, and mammals.
One thing worth knowing: the wire itself isn't much thicker. Stock 1/2 inch hardware cloth is 19 gauge, about 0.041 inch. Chicken wire is usually 20 to 22 gauge, about 0.029 to 0.035 inch. The welds and the opening size are what do the work. Our wire gauge chart has the full conversion if you want to compare.
Which Mesh Goes Where
| Part of the coop | What we'd use | Why |
|---|---|---|
| Coop windows and vents | 1/2" hardware cloth, 2 mesh, 19 ga | Air in, raccoons and wild birds out. |
| Run walls, full height | 1/2" hardware cloth, 2 mesh, 19 ga | Raccoons climb. Anywhere they can reach, they'll reach through. |
| Low coop walls, and the floor if the coop sits on dirt | 1/4" hardware cloth, 4 mesh, 23 ga | The UC Davis guide says they've seen mice get into coops through 1/2 inch holes. |
| Brooders and chick pens | 1/4" hardware cloth, 4 mesh, 23 ga | Chicks fit through bigger mesh, and Ohio State notes rats can carry off day-old chicks. |
| Run roof | Solid roofing, or 1/2" hardware cloth with a tarp over it | Keeps out hawks, owls, and wild birds, and their droppings. |
| Buried apron | 1/2" hardware cloth, 18" wide | Stops digging under the wall. See below. |
| Outer layer, optional | 1" x 2" welded wire, 14 ga | Heavier wire where dogs or coyotes push on the fence. Keep the hardware cloth on the inside. |
If rats are already a problem around the house, our guide to rodent-proofing for winter covers the 1/4 inch rule in more detail. For a side-by-side of all the stock sizes, see what size hardware cloth you need.
Cover the Run
This is the part that matters most for bird flu. Ohio State notes that hawks take birds during the day and owls take them at night, and a covered run handles both. A cover also keeps wild birds from landing in the run, and an open mesh roof can't stop droppings from falling straight through.
UC's guidance is to use fully enclosed coops with solid roofs where you can, and if your chickens go outside, to cover the run with netting or roofing. It also points out that small wild birds can carry the virus on their bodies even when they look healthy. You have three real options.
- Solid roof. Metal or polycarbonate panels. Keeps out birds, droppings, and rain. It costs more and needs real framing, but it's the best of the three.
- Hardware cloth with a tarp. The UC Davis guide lists mesh roofs covered with shade cloth in summer and a waterproof tarp in the rainy season. Cheaper and lighter. The tarp wears out faster than a solid roof, so plan on replacing it.
- Netting. The cheapest way to stop hawks. Depending on the netting size, smaller birds can still get in, and droppings always can, so treat it as the minimum.
With the rainy season starting, a solid cover over at least the feeder and the roost does double duty. It keeps the feed dry and keeps wild birds off it.
Bury an Apron
Raccoons, skunks, dogs, and coyotes will dig under a wall that stops at the dirt. The fix is a buried L of mesh along the bottom edge. UC's guidance for screening under decks and sheds is to bury the bottom edge of the wire at least 6 inches deep, extend it outward 12 inches, and cover it back over with soil. UC says that keeps out raccoons, skunks, opossums, squirrels, and rats, and it works the same way on a run.
Six inches down plus twelve out is 18 inches, and that's exactly the width of our narrowest roll of 1/2 inch hardware cloth. Run it around the base, bend it into an L, and tie the top edge to the bottom of the wall mesh with wire or hog rings so there's no gap where the two meet.
Doors, Latches, and Nights
- Use a latch a raccoon can't work. UC's raccoon guide says they're known to unhook simple latches. A latch that takes two motions, or a carabiner clipped through a hasp, is a lot harder for them.
- Lock the birds in at night. Ohio State calls this the next best prevention after keeping the flock indoors. The UC Davis guide says you can't leave a coop door open at night unless the fence around it is truly predator-proof.
- Watch the time change. When the clocks fall back in November, dark comes an hour earlier on the clock. If you lock up at a set time, move it up.
Fasten It So It Stays
- Screws with washers, or a wood strip screwed over the edge. Light staples pull out, and a loose corner is where an animal starts working.
- Overlap the seams. Lap one panel over the next by a few inches and tie them together with wire.
- Use galvanized after weld outdoors. The zinc coating seals the welds, which is where cheaper mesh rusts first. Our hardware cloth is galvanized after weld, and we explain the difference in galvanized before vs. after weld.
- Wear gloves. Cut hardware cloth leaves sharp ends. File them or fold them under.
Feed and Water
Mesh keeps animals out of the coop. Feed is what brings them to it. UC recommends storing feed in sealed, wildlife-proof containers, never leaving it out overnight, and cleaning up spills right away so they don't draw rodents, raccoons, skunks, or wild birds. A feeder under the solid part of the roof helps with all of that.
If Your Birds Get Sick
If you see unusual illness or sudden deaths in your flock, call CDFA's Sick Bird Hotline at 866-922-2473. Don't wait to see if it passes.
Frequently Asked Questions
Is chicken wire ever good enough?
For keeping chickens in, yes. For keeping predators out, no. UC and CDFA both recommend hardware cloth on the coop instead.
Should I use 1/2 inch or 1/4 inch hardware cloth on a coop?
Both, in different places. Use 1/2 inch in 19 gauge for the walls, windows, and roof of the run, where raccoons and wild birds are the concern. Use 1/4 inch low on the coop, on the floor if it sits on dirt, and around chicks, where mice and rats are the concern.
How deep should I bury hardware cloth around a run?
UC's guidance is at least 6 inches deep and 12 inches out, bent into an L and covered with soil. An 18 inch roll covers both.
Do I need a roof on my chicken run?
If hawks, owls, or wild birds come through your yard, yes. A solid roof is best because it also keeps out droppings and rain. Mesh with a tarp over it is the cheaper option.
Will a covered run keep bird flu out?
Nothing can promise that. A covered run cuts down contact with wild birds, which is one of the steps USDA and UC recommend. Clean boots, sealed feed, limiting visitors, and watching your birds every day are the rest of it. Your vet or local extension office can help with a full plan.
We cut hardware cloth to length, so you're not buying a 100 foot roll for one run. Our 1/2 inch hardware cloth is stocked in widths from 18 to 72 inches, and 1/4 inch in 24, 36, and 48 inches. Send us your run dimensions and we'll quote it. Want to feel the difference first? We'll mail you free samples of both. Family-owned since 1938, when we started on Howard Street in San Francisco. Now we're in Hayward, and a real person answers the phone at (510) 887-8787.
This article is general information about wire mesh, not veterinary or animal health advice. For a sick flock, call CDFA's Sick Bird Hotline or your veterinarian. Check your city's rules on backyard poultry before you build.