I don't blame you at all for worrying about the wiring. I really do think you can do fine without additional heat. I was thinking about the floor after I posted. If you didn't want to re-floor the whole thing, you could easily put in say half a sheet of plywood just up on 4 x 4 pieces and make sure there's straw or something under it. Then put the bedding on it as well. That would keep it a bit insulated from the concrete. Of course, you might have the issue with poor Stumpy not being able to get to it either 
Maybe a longish ramp? It shouldn't be too big a grade if it's fairly long and only has to rise 4 inches. The thing about the concrete is that it not only gets cold, it holds the cold. I remember hockey practice indoors in an unheated rink back in Manitoba...it was usually way colder inside than out! Since the floor is covered, it won't get any solar heat at all, even from the weak, wintry sun so it'll just be cold all the time. That'll be a help in the heat of summer but a hindrance in the winter. Lots and lots of bedding under them and their fluffed feathers on them should keep them fine 
For Stumpy (and whoever else wants to share) you might make a 3 sided box with sides 4 to 6 inches tall...that will help hold the bedding in spot and make it thicker there. Just a thought...
I think your idea for the box around the water is excellent! I should think if you keep some insulation all around it you'd have much less chance of it freezing. You'd still need to check it through the day as the temp changes, but I think it would help a LOT! Might be a good idea to put something under the waterer as well...to keep it off the concrete. Even a stand made with a bit of ply or a couple of 2 x 4's with straw under it would help a lot. You might want to also offer them a level perch...they may well want to roost there and they can sleep easier if they don't have to check their balance.
For our coop door, which is in the floor since the coop is elevated, we originally cut a piece out and hinged it, rigged up a pulley so we could raise and lower it from the outside. We re-worked that though...for one thing the floor is 3/4 ply and it was really heavy. Secondly, the configuration didn't allow us to put cleats clear to the bottom so it was harder for the girls to climb. We ended up replacing it with 1/4 inch ply and configured it so we could put cleats on it all the way to the bottom and now they scamper in and out at will, and it closes snugly to keep them safe and draft free at nights.
Keep us posted...I'm eager to see what you come up with!
Maybe a longish ramp? It shouldn't be too big a grade if it's fairly long and only has to rise 4 inches. The thing about the concrete is that it not only gets cold, it holds the cold. I remember hockey practice indoors in an unheated rink back in Manitoba...it was usually way colder inside than out! Since the floor is covered, it won't get any solar heat at all, even from the weak, wintry sun so it'll just be cold all the time. That'll be a help in the heat of summer but a hindrance in the winter. Lots and lots of bedding under them and their fluffed feathers on them should keep them fine For Stumpy (and whoever else wants to share) you might make a 3 sided box with sides 4 to 6 inches tall...that will help hold the bedding in spot and make it thicker there. Just a thought...I think your idea for the box around the water is excellent! I should think if you keep some insulation all around it you'd have much less chance of it freezing. You'd still need to check it through the day as the temp changes, but I think it would help a LOT! Might be a good idea to put something under the waterer as well...to keep it off the concrete. Even a stand made with a bit of ply or a couple of 2 x 4's with straw under it would help a lot. You might want to also offer them a level perch...they may well want to roost there and they can sleep easier if they don't have to check their balance.
For our coop door, which is in the floor since the coop is elevated, we originally cut a piece out and hinged it, rigged up a pulley so we could raise and lower it from the outside. We re-worked that though...for one thing the floor is 3/4 ply and it was really heavy. Secondly, the configuration didn't allow us to put cleats clear to the bottom so it was harder for the girls to climb. We ended up replacing it with 1/4 inch ply and configured it so we could put cleats on it all the way to the bottom and now they scamper in and out at will, and it closes snugly to keep them safe and draft free at nights.
Keep us posted...I'm eager to see what you come up with!
