Avoid Rotten Posts
If you have to put a wood post in the ground, bury the uncut, factory-treated end.
In my opinion, you should never install a wood post in the ground if you don’t have to. Instead, use concrete underground with the post itself above ground level to avoid rotted wood. But if you have to bury a wood post, I’ve found that the most effective and simplest method to achieve a long-lasting post is to bury the uncut end and leave the cut end above ground.
The factory’s pressure treatment adds deep penetrating protection, but you can’t assume that the chemicals are reaching the very center of the post. Cutting off the factory end can expose the untreated center, which will lead to rapid rotting. Dabbing a little preservative compound on the cut end is not going to give you the same protection as a factory pressure treatment. I’ve torn apart decks where the posts that were buried with the cut-end down were completely rotten, but the posts buried factory-end down still had a tag on them when I dug them up—on the same deck! So if you have to bury a post, always stick the uncut end in the ground.
—Grant Litts, Norway, Mich.
Edited and Illustrated by Charles Miller
Published in Fine Homebuilding #309