Re: Boat paint for decks?
The problem with painting and sealing decks is the nature of the deck construction itself. There are just too many places where moisture can enter into the wood: the bare bottom of the decking boards usually sit on bare wood of the joists ( they shouldn't be, buy usually are) so that moisture is passed up into the decking. There are butt joints which will never be able to be painted again once the deck is finished, there are hundreds of decking screws which are usually over-torqued and sit in little craters which allow water to sit for days, etc.
The import of this is that moisture gets into the wood. Then comes the heat of spring and summer with the sun beating down onto the deck. Vapor pressure is created and if it cannot pass through the paint film fast enough, peeling will occur. This is why marine paints are not a good choice for decks - it does not breathe! Acrylic decking stains are able to pass moisture on through the film without causing peeling, assuming that a good bond was create when the deck was stained. Oil paints in general are vapor barriers, acrylics are much less so.
Every now and then I have a customer state they want to varnish their deck. I tell them they will have a beautiful deck this year - and next year it will peel! SAme reason, an oil varnish is a vapor barrier.
RustOleum sells a product called "Restore" which puts a 40 mill thick, acrylic coating on your deck. It is fortified witha sand like grit which will totally fill screw craters and any splitting of the decking boards. The concept is that it totally blocks water infiltration from the top side. If you don't like a sanded texture, you will not like the looks of it. However, it does a good job of holding on troubled decks. It also gains a few more years for decking which is getting long in the tooth. It can close a 1/4 inch split in the wood.
Otherwise, stick with an acrylic decking stain. Don't forget to seal the underside of the decking , if it is accessable. Unfortunately, decks are not low maintenance items. Here in Portland, Oregon, I chose to go with a concrete patio vs. a deck. Oddly enough, back in my native Chicago, I would have gone with the deck over concrete because of frost heaving. Also, Portland's mild, wet winters are actually much harder on decks and exterior wood than is the very cold, dry Mid-West winters. Here decks get rained upon all winter long, followed by hot, dry summers.