I have this playhouse, in the other style that's blue. Also got it form Lowes for $199. It's WONDERFUL. I built a very solid floor out of 2x4s and 3/4" plywood, put it up on cinder blocks, and attached the house to it. The sides are 1/2" and quite sturdy. The frame is 2x2s. The house itself, once built and on a floor, is VERY sturdy and I'm amazed how warm it is inside. I have no problem walking around in there, but I'm 5'4". My son is 5'11" and he was in there, too, no problem. Not that I'll be in it too much; it would be very easy to fluff up the shavings from the doorway.
I stapled a tarp down before I put the shingles on the roof. You could just as easily do roof paper. I plan to insulate the walls a bit more with 1/2 plywood on 3 walls. That's also what I used for my nest box, which is on the outside. So my nest box is attached to the regular wall and 1/2 plywood on the inside of the coop. It's very sturdy.
My coop is for 5 hens. I was going to have 4, but I think 5 will be fine in it since they will also have an attached run that's 16x4 and their door will always be open. Anyway, I'm really excited about all this, it's my first flock! I get my girls in May.