Pressure Treated Deck Boards - what side up

Going to put down the deck boards. Wondering what side should be up? The bark side or the other side?

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Jun 10, 2011
I prefer the bark side down
by: Editor - Rich Bergman

I usually install the bark side down. This is more important when you are using harder or stronger woods that have greater pulling power as they dry out. This means pine is a candidate for this technique.

Softer woods like cedar or redwood are less of a worry because they can usually be held secure with screws.

The reason I put the bark side down is because when a board dries out and if it start to "cup" it will do so because of the tension caused by each growth ring reducing in thickness a little bit.

The rings closer to the outside of the log, nearest the bark, are longer - the diameter is longer, the radius is longer - and so when they reduce in thickness they cause rings to straighten out a bit. They pull and the only way the board can equalize these forces is for the inner rings which also become thinner but have a shorter radius is to straighten out towards the bark side.

So if they cup, atleast the top side or inner part of the tree gets a bit of a dome or crown to it and this actually encourages water to drain to the side of the board.

Install the board the other way and you get an invereted cup and the water collects and you eventually get rot.

This is not much of a worry with boards that are quarter sawn or have more vertically oriented grain lines. That is a very stable cut. Hope this helps. If there is a builder out there with other experience please share.

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