Product Description Once applied, Smartseal wood sealer creates an invisible waterproof barrier that will help prevent the ingress of moisture on ingress on pressure treated softwoods such as fences, sheds, garden furniture and decking. The wood waterproofer is specially formulated to protect your outdoor wooden surfaces for up to 10 years. The water-resistant surface will also inhibit the growth and spread of mould and algae which is a big problem with softwoods, especially in shaded north-facing areas of locations with high levels of rainfall.