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?
(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.
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.