We just moved into a new house a few months ago and now we are starting to think about dealing our new back deck. I read several threads that said TWP is a good product, so I'll probably go with that. I want a product I can reapply every year or two without stripping, so it seems like TWP fits that bill. My question for the seasoned professionals is do I need to seal the underside of the deck? We have a walkout basement which has a concrete patio below the deck, so when you walk out from the basement you can see the bottom of the deck. I want to make sure I do it right, but if sealing the underside is not important I don't want to waste money on the sealer, since it's expensive. I have pictures if anyone is interested. I appreciate your help.

Bob