Pressure treated deal
Lifetime preservative treatment
Pressure treatment is a lifetime preservative treatment. The preservative is forced into the timber under pressure and penetrates below the surface, whereas all other treatments apply a coat of stain to the surface of the timber only. Pressure treatment is almost colourless except for a slight green tint caused by the copper content in the preservative. No further treatment is ever needed but if you want a coloured finish you can paint over pressure treated timber with normal wood preservative in any colour. The picture shows pressure treated shiplap.