Pressure-treating wood adds copper sulphates, arsenic and other chemicals to wood, in order to keep away termites and to help reduce the likelihood of the wood rotting. There is no UV or other weather protection in the pressure-treating process – the pressure-treated wood is just as susceptible to the damaging effects of the sun and weather as raw wood. Only by applying a UV protecting sealer / stain, such as those we use, can your pressure-treated wood structures be protected from the sun and other damaging weather elements. The additives in pressure treated wood are often a skin irritant – especially for children and people with respiratory problems. Sealing pressure treated wood ensures that the additives are sealed in so that they cannot irritate people, especially small children, and pets.