Are you putting this wood in concrete? If so, an alternative might be setting the wood into brackets designed to hold wood on concrete, OR those little concrete blocks you can buy for $3-$6 each that would hold the wood above ground. Because we're beuilding our run in a frost zone we'll use sono tubes, concrete and U-fittings to accept the wood over the concrete. We'll use a few treated 4x4's (because we have them) on the corners where the chickens can't reach them. Like others we're cautions about sawduct from treated wood- we use a face mask when cutting and we always cut in a location away from the animals.