We're looking for a durable but lightweight covering for the tops and sides of our chicken tractors, which are 10'dx12'w. We're starting to think about Tyvek house wrap. As far as I know, it's tough and puncture resistant, waterproof, it comes in white so it'll reflect the sun, and it's relatively cost effective provided it lasts a couple of seasons. I can get it in 8' rolls, which is enough to use one width for the roof without having to do any overlaps or seams. I was thinking I still need to figure out a "joist" system to prevent sagging during heavy rains, a problem we had with regular tarps. But does Tyvek even stretch under pressure? OTOH, the new chicken tractor design will have a pretty severe angle to the roof--maybe 4' at the front down to 1-2' at the back--kind of a leanto design. So I'm thinking there may be no need to worry about sagging, but maybe I'm wrong? We usually cover the roof with chicken wire before adding the tarps. As far as attaching it to the tractor, I'm thinking sheetrock screws with plastic washers where the screws hit the Tyvek. I can predrill the holes if the screws will twist the Tyvek when I'm putting them in. Nails are not an option due to the stress on the chicken tractor every time it's moved. Anything I'm not thinking of?