Rot Resistance of White Pine Versus White Spruce

Unless it's old-growth heartwood, neither species is particularly durable in outdoor exposures. March 28, 2010

Question
We are putting an outdoor staircase on a barn and I have a bunch of eastern white pine that is dry ready to build it with. The client has a bunch of white spruce logs that he thinks would be better to use than the white pine. I realize neither species is really suited for the application, but which will last longer, spruce or pine?

Forum Responses
(Sawing and Drying Forum)
From contributor Y:
Hoadley lists EW pine as moderately resistant to decay and spruce as slightly or nonresistant. My shop door is made from untreated and unfinished EW Pine, and although it's only about 4" off the ground, it is just starting to rot at the bottom after 30 years. From personal experience, I'd say use the pine if it's all heartwood. The NW cedar shingles that were next to the door actually rotted before EWP door.

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From Gene Wengert, forum technical advisor:
Please note that the US Forest Service (which is what Hoadley based his work on) only lists the natural decay resistance of heartwood. In pine, that would be the reddish colored wood. However, most of the time we use the white colored sapwood on pine and the decay resistance is minimal. Further, today's heartwood is much less resistant that the virgin pine that was evaluated by the US Forest Service. So, unless you use pine heartwood, you will not see an appreciable difference between E. white pine or spruce.

Both will last a bit longer if they are protected from direct wetting and also can dry out after any wetting. Many pieces may last for a long time, but it only takes one failure for a serious accident to happen. You would probably best avoid providing any wood for such a risky project and also avoid giving oral advice that is not accompanied by a written document acknowledging the risk and the professional advice you give to avoid using either species.