That coop is too nice! I love it. You really went all out (as in you maybe went overboard before you knew what you were in for...?
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It certainly gets major cute points. Whoever built it has got it going on.
Bad smelly means you gotta clean out the litter or rake it, lime it and cover it with more. This is called the deep litter method and is something you should look into.
Someone else noted the first thing I did - no vents. Ventilation is crucial. Everything from mold and fungus to lung disorders can result without it. Chicken housing should be "airy" unless you live in the arctic and you need good turnover of the interior air volume. Cut some plentiful vents in there, get screens on those windows and open 'er up...
Definitely do removable dropping pits. These are slide out drawers that go under the roosts, which you remove out the side for cleaning. And eliminate the rafter roosting. You gotta control chickens if you want to control their wastes. Letting them roost wherever only makes more work for you.
Finally, the birds need to stay outside except to sleep and lay eggs. Permanently sited coops should offer enough secure space for roosting and laying and little else. Basically, they should be off limits until dusk. Feed and water them outside during the day.
Mine live in a fresh air tractor-style house, in an enclosed pen area. I have about 100 sq ft per bird total and the coop is mobile, moving from area to area. This lets the earth help me eliminate the poo. Im a firm believer in "Fewer Birds Are More."
In our rush to have chickens, something often glossed over is the "poo problem." You have followed the "4 sq ft Rule" and now feel what it really means. It actually evolved from the modern commercial business and is intended for roosting/laying coop space only. It is one of the most cited "Rules" and does most of us, and our chickens, a dis-service.