I am very new to all this and therefore have a myriad of questions. Having just retired in March of 2014 I am looking into starting a CSA (Community Supported Agriculture) mini farm and raising meat and layer chickens to supplement our produce. I am not in a hurry to make a mess of things so I spend a lot of time surfing and researching the web and particularly this awsome site. I've selected an area where I plan to build either a permanant coop or a chicken tractor so now I need to check into the designing features. I've surfed the web so much on the subject that my hair has turned blonde and my toes can hang five around any type of roost or board. One thing that I have noticed is the construction of most coops and tractors being strong enough to withstand anything short of an atomic blast. Why is this? I am a general contractor by trade and was under the impression I could use materials with a much stronger strength to weight ratio and at a more economical cost. Is there a tried and true design the requires the use of such heavy and degradable materials? I love the various designs I've viewed but do not understand the use of 2 x 4's, 4 x4's, 3/4 inch osb and such especially for the tractors.