I've recently completed power washing (gently) my deck and screened porch. I've already re-stained the deck, but several of the vertical wooden surfaces on the porch had some peeling paint. The house is only 5 years old, and the original paint is an outdoor quality latex or oil-based paint. I intended on simply filling and repainting these areas, but is there anything else I should be concerened about? I believe all the deck/porch should be pressure treated / 20.
It's possible that when you pressure washed the porch, the siding got wet and that's why it's not holding paint. Paint and water don't really mix. The best approach is to completely sand and scrape the loose paint, spot-prime those areas and then repaint. Otherwise the new paint won't stick.