We have evolved to use Cuprinol garden shades, a water based paint, for the coops. Dries quickly and is waterproof in two coats. Fairly flexible so it accommodates wood movement but does need recoating every year or so. It is non-toxic and comes in lots of nice colours. Traditional creosote is very toxic, difficult to get, smells for ages and is dark brown. We only use it for red mite control inside and the coops get aired for at least a month when dismantled before reassembly and putting birds in. Rain runoff is toxic and contaminates the soil. This is why it is now banned for general domestic use. Last time used it burned my hands, which took 3 days and loads of cream to stop itching.