I'm debating between the "Garden-Coop" plan and building a playhoouse style walk-in coop. I have some used windows already but I built a nice playhouse a couple of years back for my boys and remember the T1-11 siding (looks nice, has grooves in it) being really expensive @ $40 or so a 4'x8' sheet. The walk-in coop for dummies calls for 11 sheets! To me that is going to be the biggest expense. Does anyone have any suggestions for cheaper siding alternatives (that isn't painted plywood)? Cheers.