The issue of the rotting posts lies in the tree growth rings and their location.

Dear Maintenance Men: I am replacing a number of rotted, pressure-treated 4x4 fence posts on my property. Why do some posts rot while others do not? I cannot see any rhyme or reason for one post to be good and the other bad. How can I avoid this trouble in the future?

Kent

Dear Kent: The issue of the rotting posts lies in the tree growth rings and their location. If you look at the 4x4 post end, the growth rings will be either centered or not centered. Your rotting posts may have centered growth rings. When buying pressure-treated post, always look for off-center growth rings.

Here’s why: A centered growth ring is common in posts made from a peeler core. A peeler core is the by-product of plywood manufacturing: A log is turned on a lathe to produce plywood veneer and the center that remains is called a peeler core. The tight centered growth rings of the peeler core will not accept pressure treatment as well as a post with off-center growth rings. Chances are that the fence you are repairing has a mixture of peeler core posts and off-center growth ring posts.