That first one has possibilities but I don’t know how structurally sound it is. My main concern would be if the support posts are rotten at ground level, but also consider the condition of the other main wood and roof. Some of those old structures can last a long time. If you drive through the country( not so much on the interstate) you can see some really old buildings. Part of that depends on what wood was used and part is how dry they stay.
I think you are talking about building a coop by enclosing one of those bays. You can stiffen that up a lot depending in how you build your walls but how sound is the rest. If the main support wood is not rotten and it’s been there a long time, it may not be as much as a risk as some people think. It hasn’t blown down yet.
I don’t know where you are or how much of a winter you would face, but I could see building 8’ high walls out of something solid with the wood framing stiffening it up and use wire on to the top. That would give you outstanding ventilation and if your roosts are low enough they would be out of any direct wind.
Looking at the second structure, are you sure that’s not an old smokehouse? That open space in the floor could be where they built a fire. I don’t see a lot of ventilation up high that was built into it but maybe there is and the photos don’t show it. A smokehouse would not have ventilation up high. That raised floor looks like the wood isn’t that old though. I’m not sure what’s going on there. Is that floor a later addition?
I’ve seen old milk sheds with something like that too. Maybe someone was milking cows or more likely goats?
I can see sunlight coming in through the wall, so you would need to do some repairs. You could put board up the inside but you need to keep rainwater out of there. If water can get inside it can cause rot. The wood getting wet is not the big problem as long as it can dry out. The wood staying wet is what causes the problem.
You can see sunlight under part of the foundation, so might need to do some work there. I’m not sure how big a problem that is.
As for the varmints, that is probably a groundhog but other things like skunks can do that too. Possibly a fox. I would not expect a raccoon to dig a den in the ground but they might use an existing den. A lot of other things could use an existing den too. I don’t know if that is active but groundhogs love to den under buildings like that. Mom had that problem under one of her outbuildings and a neighbor recently took four groundhogs out of a den under one of his.
The groundhogs themselves would not be a direct danger to your chickens but their tunnels could be an avenue for other things to use to get inside. They like to hide the openings in brush piles, under buildings and things like that so there would be no reason for them to tunnel into your run, but who knows. If you put a floor in there, even at ground level, there is a chance something will den under there. It’s possible nothing is using those dens right not, but groundhogs tend to use a den for a long, long time.
You can put a secure floor in there and you should be OK. The only way I’ve seen people get rid of groundhogs is to shoot or trap them out, and there could be several in there.
Both have possibilities and both have some questions. If they are still structurally sound either could work. Good luck.
