Is There a Way to Rotproof a Lamppost?

Q: "Is there any way to make a wood 4x4 lamppost rotproof?"


Is there any way to make a wood 4x4 lamppost rotproof? My brother has replaced his driveway lamppost three times, even though he coated the buried end with wood preservative each time. A vinyl or metal post is out of the question; he wants a traditional look.
— Ted, Bloomfield, CT


Tom Silva replies: Any wood in contact with the ground will eventually rot, even pressure-treated lumber. All you can do is slow down the decay process by using rot-resistant or pressure-treated wood and by tamping a fast-draining mix of soil and pea gravel (or gravel and stone dust) around it.
But if you really want a wood post to last a long time, don't put it into the ground at all. Instead, pour a concrete pier with a depth equal to one-third the post length, and embed a galvanized or powder-coated metal post base in the wet mix. Then after the concrete has cured for a week or more, bolt your post to the base. To help the post last even longer, before you bolt it on, soak the end grain of the bottom of the post for an hour in a container filled with water-repellent wood preservative.


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