Staining Undersides of Deck Boards 5/5 (3)

by Deck Stain Help

Updated February 2020

How to Stain Undersides of Deck Boards

Welcome to, your source for the latest tips, tricks, deck stain industry insights. This is an update for our previously published article, discussing whether or not you should stain the underside of deck boards in 2020. We want to hear from you. Leave us a comment and tell us if you recommend staining the underside of deck boards, and why or why not.

Do You Need to Stain the Undersides of a Deck?

Bringing up some debate is whether or not you should stain the undersides of a deck. It is common and advisable to stain the weather-exposed surfaces of a deck to protect them from water and sun damage. But do the undersides of a deck also need to be protected?

Protecting the underside of a deck from the sun is not an issue since the underside of a deck is always shaded, but what about protection from moisture? Moisture is absorbed into unprotected wood causing it to swell. Once the wood dries out, it shrinks back to its normal size. Over time this constant swelling and shrinking cause deck boards to warp, crack, and split.

Obviously, the exposed upper side of a deck is much more susceptible to moisture and water damage caused by rain and even morning dew. Although the underside of a deck may get a little wet during a good downpour, it certainly is not as likely to get wet.

The dilemma with applying stain to the underside of a deck is time and the cost of doing it. In some instances, it is almost more work than it is worth. Staining the undersides of boards can be very labor-intensive and will double the stain cost of the deck-staining project.

There is also some debate about moisture being trapped if all sides of deck boards are stained. This varies by opinion but all boards should be able to breathe. Whatever the case, it seems that just staining only the top exposed surfaces of a deck make the most sense.

One acceptable reason to stain the underside of a deck would be for appearance especially on an upper-level deck where the underside is more noticeable.

In the experience of most deck staining professionals, staining only the exposed surface of a deck is adequate in protecting the wood. If you want some of the beams, posts or more exposed underneath portions of the deck stained strictly for appearance then that is up to you. But as far as protecting the wood, it is not necessary to stain the underside areas of a wood deck.

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Hi, I’m replacing a rotten deck surface with kiln dried Douglas Fir (not pressure treated). I had planned on staining all sides of each board before installation in order to fully protect them from the elements. Extensive reading of this site and several others indicates I should install the boards, wait several months and then stain. This makes me nervous. The deck is located in Wisconsin, is uncovered, gets sun for half the day and is exposed to the elements. Is it really ok to build the deck unstained, leave the boards exposed to rain and sun for 2-3 months and then clean and stain it?

I really appreciate the advice. The site is a great resource.


We live on Smith Lake in Alabama. We will be applying a new treaded pine deck to a floating dock.
What would be the best stain to use and should we coat both sides of the boards before applying?


Since a portion of the dock is an uncovered swim platform, which stain will stay the coolest on bare feet?


Regarding solid stain, how have light colored stains, like whites, off whites, worked/looked/ held up for deck rails (not deck floors), or fences?

Margaret Amundson
Margaret Amundson

I have had two failed decks. The newest one is of cedar and is several months old. It is starting to gray. We live in Michigan and the deck gets full sun. Would Armstrong Clark Wood Stain be the best choice? I want to have this done before winter. We have had the deck roped off so it is still clean. What prep do we need to make??/ Thanks.