Rot-Proofing a Lampost

Tom's advice on making your new post last longer

The This Old House crew
Photo by Webb Chappell

In front of my daughter's home, there's a picket fence that terminates at a wood lamppost. The post has rotted, but I can't seem to find new lampposts made of any other wood than pine, which I don't think will last very long. What do you suggest?
— A.C., Emmaus, PA


Tom Silva replies: Have you checked with stores that specialize in selling lighting fixtures or that make custom fences? You'll often find that they sell wood lampposts, too. Look for posts made from the heartwood of cedar, cypress, or redwood, all of which will be more durable than standard pine and look better than pressure-treated pine.
Of course, even these woods rot eventually, but there are a couple of things you can do to improve the post's durability. Start by soaking the bottom of the post in a copper-based wood preservative such as Cuprinol to seal out water and minimize rot. Just pour the preservative into a bucket and stick the post in it for a couple of days. Use a brush if necessary to spread the preservative up the post to a point an inch or two above grade level. Wear rubber gloves and goggles when working with this material, and be sure to follow all the application instructions. After the preservative dries, slap on a layer of asphalt-based foundation sealer over the portion of the post that will go into the ground. Let this dry for a week before putting it in the ground.
That takes care of the post, but you also need to prep and fill the hole right. Dig it at least 3½ feet deep, or 6 inches deeper than the frost line, then fill up the first 6 inches of the hole with pea stone, and tamp it down with a 2x4. The pea stone encourages drainage and prevents water from collecting at the bottom of the post. After you put in the post, backfill around it with pea stone tamped down in 3-inch-thick layers. Mix a little soil in with the pea stone so it will tamp down better. If the surrounding soil drains very well, you can use a mix of stone dust and gravel instead of pea stone and soil. Don't set the post in concrete, though; it holds moisture against the wood, which accelerates decay.


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