Cuprinol ultimate garden wood preserver has a superior formulation that works in 3 ways uv filters give long lasting colours for up to 5 years added waxes resins provide advanced weather protection and active ingredients penetrate deep into the wood top protect against rot decay and blue stain it can be used on all types of rough or planed wood such as sheds fences summerhouses gates and arbours how much do you need 4l covers up to 20m on smooth planed wood and 12 16m on rough sawn wo