Keeping the Coop Dry: The Ammonia Problem and How to Prevent It

Open the coop door on a warm morning after a damp week and you may get hit with a sharp, eye-watering smell. That is ammonia, and it is not just unpleasant. It is a sign that the air your hens breathe all night is harming them. Because a Speckled Sussex flock is made up of large birds that produce a lot of manure, the problem can build faster than keepers expect. The good news is that ammonia is largely preventable, and the cure is mostly about water.

Here we look at where ammonia comes from, what the numbers say, and the habits that keep a coop dry. Our guides to bedding and cleaning and coop design cover the supporting details. For local poultry events and suppliers, agriculture.directory can help.

Where Ammonia Comes From

A University of Georgia poultry tip on making sure ammonia levels do not harm the flock explains the chemistry plainly. Bacteria in the litter break down uric acid from droppings, producing ammonia. Manure, heat and moisture all contribute, and moisture is the biggest problem. Wet litter, the document says, almost guarantees ammonia problems. The same source notes that insulated, airtight housing traps moisture and ammonia because it limits fresh air exchange.

That last point explains why so many keepers get it wrong in winter. Sealing the coop to keep birds warm backfires, because the moisture from breath and droppings has nowhere to go. A tight, warm, wet coop is an ammonia factory.

What It Does to Hens

The Georgia document says ammonia irritates the respiratory system, with symptoms including coughing, sneezing, eye inflammation and labored breathing. It also reports that feed intake drops, and that combined with heat stress, feed efficiency worsens. It gives a rule of thumb for people: most of us can smell ammonia at about 20 to 25 parts per million, and if you can smell it, the coop needs corrective action. It suggests ammonia should not exceed 25 ppm, and says prolonged exposure to as little as 20 ppm can harm bird health and performance.

Those thresholds come from production poultry guidance, but the principle carries to a backyard coop. Your nose is a rough detector. If your eyes sting when you lean into the coop, the hens have already been living in it for hours. Chronic low-grade irritation also opens the door for respiratory disease. If you see persistent sneezing, wheezing or swollen eyes, contact a vet. Do not guess at treatment.

The Real Fix: Dry Litter

The University of Kentucky bulletin on managing poultry litter aims for litter moisture of roughly 40 to 60 percent and says wet litter is the main concern, because it raises ammonia and can cause foot dermatitis and chest lesions. It also notes litter can become too dry, especially in low humidity or at low stocking density, and that lightly adding water corrects it. The point is balance. A crumbly handful that holds together when squeezed but breaks apart is about right. A sodden clump or a dusty powder is not.

Find the water

Walk the coop and ask where the moisture is entering:

• Waterers. The usual culprit. Raise them onto blocks or mesh, or move them outside the coop. Fix drips right away.
• Roof and wall leaks. Check after every storm. A small drip into the bedding can wet a patch for weeks.
• Ground moisture. A coop built on bare earth wicks damp up. Raise the floor or use a solid base.
• Breath and droppings. Birds exhale a lot of water overnight. Ventilation has to carry it out.
• Wet birds. Hens tracking mud inside bring water with them. Keep the run drained and give them a dry covered area.

Ventilate, high and open

Ohio State's winter care fact sheet advises blocking drafts without sealing the coop completely, and controlling airflow so ammonia and moisture do not build up, since both raise respiratory disease and frostbite risk. If you hang tarps over open sides, keep them below the roofline so air can still move. In practice that means vents high in the walls above roost height, kept open year-round. The Georgia document also suggests monitoring relative humidity, aiming for about 50 to 70 percent, and using a small fan to circulate air and dry the litter if needed. A cheap hygrometer is a useful tool.

Daily and Weekly Habits

1. Droppings board. Scrape it every day or two. Most manure falls at night under the roost, so this removes a big share before it reaches the bedding.
2. Spot clean. Remove wet or caked patches, especially under waterers and near doors.
3. Stir. Rake or fork the litter weekly to break up crust and let air in.
4. Top up. Add fresh dry bedding when the surface looks tired.
5. Sniff test. Stand in the coop with the door closed for a moment each morning. If it stings, act.

Stocking Density Matters

More birds mean more manure per square foot. The Kentucky bulletin lists minimum floor space for deep litter of roughly four square feet per large-breed bird. Overcrowding a Sussex coop puts moisture and nitrogen into the bedding faster than the system can handle. If your litter keeps going wet despite good habits, count your birds and measure your floor.

What Not to Do

Do not mask ammonia with scented products or heavy covers of lime or other additives without advice. Dusty powders can irritate lungs too, and covering a wet floor does not dry it. Do not seal the coop. And do not ignore hens that are sneezing. The Georgia document recommends testing air quality with a nose check, test paper or gas detection tubes, and contacting your county agent if you suspect a problem you cannot resolve.

Keeping a coop dry is dull work, mostly leaks, waterers and a rake. But it pays off in healthier lungs, cleaner eggs and fewer winter troubles. For a humor break, farm.fm has a piece on a farm life influencer and 4 a.m. chores, which may sound familiar the next time you are scraping the droppings board at dawn.