Exterior wood preservers are designed to protect garden sheds and other garden wood from biological threats such as mould, algae, wood rot and insect attack. Whilst many wood preservers do contain a small amount of wax, they generally only offer limited weather protection. We recommend that any exterior wood is treated with a preservative first then a suitable exterior wood oil. Decking oils such as Manns Premier UV Decking Oil or Ronseal Decking Oil are ideal for use on garden sheds.