we bought our house from the bank-it was reposessed. It looks like the deck was never taken care of. It is green treated wood. I have pressure washed some of it with a little electric one and it did decent. The paint is so frail I can pick it off with my fingers in most places. The wood is not in the best shape, some places are lifting, prime splinter candidates. Before we bought the house they tried to cover the deck with paint-it rubbs off with alcohol so I assume it is latex. The places that I have already cleaned look much much better. Under the paint is a green layer (mold??) that with a little power comes right off. I think it will look in much better shape when I get the paint off and see completely what I have. I beleive you are correct that there is some rotting, but I believe it is just the very outside layer and can be fixed. There are also some holes where knots were in the wood, can I fill those with wood putty before I stain?? When they painted the deck they sprayed it- and everything else around it-inlcuding the vinyl siding-but that is another struggle entirely-tedious scrubbing with fair results.