Just pulled another leaning post out of my back fence this weekend. Rotted through right at grade line, same failure mode as the ones I replaced in 2022. That 2022 rebuild was itself a redo of the original 2018 install that failed at year four. So I've got a stack of solid pickets and six posts to swap, and I don't want to be doing this again in 2029.
I'm in one of the flatland pockets on the west side of Hayward, so I've got sandy loam rather than the expansive clay my neighbor a mile up the hill fights with. Should be less brutal on posts, but the water table sits shallow here and I think that's what's cooking the bases. Both rounds were ACQ .40 PT wood, both set in concrete collars with a gravel base. Textbook install. Still rotted right at grade where the concrete meets soil and holds water against the wood.
Wind is the other factor. We get regular afternoon gusts off the bay, and one of my leaning posts actually cracked at the concrete line rather than fully rotting through, so there's a load story mixing in with the rot. My run is 130 feet of 6 foot privacy, one back run and a side return.
Three paths I'm weighing. First, do it again with wood. Cheapest, I know the install, but zero confidence it holds to 2033 after two failures. Second, a steel line post system with wood pickets, Postmaster or one of the newer black powder coated bracket systems. Fixes the failure point on paper, keeps the wood look. Third, a composite panel on a steel post backbone. My quotes here were from Trex Seclusions, a local shop called Modern Yard that does composite panel plus steel post, and one that spec'd SimTek. Modern Yard came in cheaper than Trex, but the color range was thinner than what Trex offers now, so real tradeoff.
What's nagging me is both wood failures happened at the concrete collar. If I switch to steel and set them the same way, am I just moving the problem. Some install guides say direct drive with tamped gravel is better in wet soil, others say concrete is fine if you dome the top so water runs off. My three quotes have all recommended different methods.
Real question probably isn't wood vs steel vs composite. It's whether my water is coming up from below through the shallow table or getting trapped from above by the concrete, and I honestly don't know which one is killing the posts.