Coop (Dampness)

Wow 20 chickens sounds like a lot to me. I have six hens in a 4 X 6 coop with a 9 foot x 20 foot run plus the underneath of the coop and still think that's to small for my girls... I gave up after three days with pine shavings in the coop. There was no way to keep it clean. I cleaned it every day. I've since switched over to using sand and pdz in the coop. The girls and I love it! Wow what a difference cleaning the coop it has been. I just use a kitty litter coop on an extended stick. Takes me maybe two minutes a day to clean.
I'm new to raising chickens and want nothing more than to keep my girls dry and clean.
Do you have lots of ventilation above your girls when they roost for the night? Poop trays under the roosting boxes? Windows to open during the daytime?

 

Do u have a run?? I recommend leaving your waterers in the run if u already aren't. I also Would put up poop boards under the roosts and that will keep the moisture down too. It seems like your coop is a little full that can be an issue sometimes with bullying.

 

Sounds like over crowding may be part of the problem. How much ventilation does the coop have? I have 6 chickens, a 8' x 18' (8' X 9' for chickens, other 1/2 is storage) coop and a 8' x 16' run. We also use pine shavings with no problems. There is a poopboard filled with PDZ under the roost which helps absorb moisture from the droppings.

 

How deep are your straw and pine shavings?

 

Pic of coop please?
Probably just too many birds in too small a space with not enough ventilation.

What is your climate?
Putting your location in your profile can help folks give better answers/suggestions.