We are currently using an adapted playhouse (that we were given - free!) as our chicken coop and so far it is working well with the modifications that we made. Ours came with three windows, two of which we covered with hardware cloth and the third which was turned into an external nest box. We added a floor, two roosts, a chicken door, and mounted two bunny feeders on the wall below the front window. Ours also had the Dutch door, but not the top portion, which we added. Our 4' X 5' X 4' coop is roomy for our 3 girls. Here's a picture of before and after:
Before:
After:
The one downside we've found with our coop is that the bottom of the door isn't entirely flush and has small gaps. When it rains particularly hard, the shavings inside the door have a tendency to get wet. You all might want to watch for that with your coops as the photo at the Lowe's site shows the same kind of gaps in the door of this playhouse. If you all can figure out how to solve that problem, please share.
Before:

After:

The one downside we've found with our coop is that the bottom of the door isn't entirely flush and has small gaps. When it rains particularly hard, the shavings inside the door have a tendency to get wet. You all might want to watch for that with your coops as the photo at the Lowe's site shows the same kind of gaps in the door of this playhouse. If you all can figure out how to solve that problem, please share.