Yes, there is no problem in applying wood protection without a pretreatment. Of course the wood will not be protected against rot, termites, wood destroying worms or blue stain, unless the wood is pressure impregnated, vacuum impregnated or Thermowood®
.
It depends on whether the deck is new or old... If it is new - no. If it is old - yes. On an old wooden deck, there will be dead wooden fibres on the surface, so it is a good idea to sand it down, until the wood again appears clean, uniform and solid.
Yes. There are two reasons for sanding the surface: 1) To get a better adhesion of the layers of varnish. 2) To remove any dust from a previously varnished surface.
If you do not sand thoroughly, you may see that the wood protection does not have good adhesion with the surface. When you sand, you scratch the surface slightly, which improves the adhesion of the wood protection you apply. You also remove dead wood fibres from the surface, so you obtain a smooth and clean surface for applying
wood protection. Remember - do not use too fine grit, i.e. sandpapir with grit over 220 is not useful for our products.