replying to O Wren , BillN wrote:
Since my post above using gravel and Coppercoat, have rethought the whole thing.
What seems like the PERFECT solution is using the "SuperPost" sleeves
(available at Amazon or the company's removablepost.com website), which are hard
plastic sleeves that completely envelop the underground portion of a wood post
(including the bottom). These sleeves are permanently set in the ground using
either concrete or gravel, but the wood post is REMOVABLE. To replace a damaged
wood post, simply slide out the old one and slide in the new. There is a square
rubber gasket and cover that goes around the post to provide a watertight seal,
preventing water from getting inside the sleeve (these slide up a new post
during installation, and then are slid back down to seal against the sleeve once
the post is set inside). So the entire underground portion of the wood post
remains dry and free from ground contact (the top of the sleeve comes out of the
ground a little, which is why the rubber gasket has a brown or white decorative
cover). These sleeves come in 18, 24, and 36 inch lengths for 4 x 4 posts, and
36 inches for 5 x 5 (I think they are coming out with 6 x 6 sleeves too).
Feel free then to use a nice Cedar post for a mailbox, which when Teak or Tung
oiled above ground (every few years) should last for a decade or two (before
putting it in the ground, oil the underground sleeved part along with the rest,
just cause it's easy then and will provide extra protection). Even for
untreated Cedar fence posts though, there should not be any underground rotting.