It is not necessary to stain the underside of your deck for protection from the elements, especially if you use pressure-treated wood, which helps keep wood-boring insects out.
Should underside of deck be stained?
The underside of decks, by its very nature, never sees direct sunlight, so stain under a deck is not necessary. ... Staining the underside of the deck will prevent that from occurring on decks where the underside will be seen as a part of the outdoor living space. 5. You need to stain your deck every year.Feb 21, 2014
Should you paint the underside of a wood deck?
The underside is important because the water on your deck will dry on the top and run and hang onto the bottom. Expect to have to repaint the bottom faster than the top. But again with maintenance this is an easy job.Sep 27, 2016