when I install posts into the ground I wont use concrete.
if you use just a good gravel mix to pack in around the pole and you go a
good foot lower than the bottom of the post you will keep it from ever
getting water logged.
The gravel provides drainage. Contrete will wick moisture into the wood.
so even if there is only damp earth around the post the post will be wet all
the time and rot becomes a problem.
you can wrap your posts in 6mil poly too just like vapour barrier. I dont
bother.
If you have a good mix of Pea Gravel that is used over weeping tiles that
will keep the post solid and dry. Just tamp the gravel after every 6inches
or so as you put it in.
And just as a side note I usually make sure I have 4 feet of post in the
ground.
it just wont tip then.

Doug

"Phisherman" wrote in message
...
I am building a garden gate and frame out of PT lumber. The gate
frame is two 4x4s that hold a 4x4 cross member as so:

| |
| |
| |_____ground level_______
|----|
| |

How can preserve the underground members so that they will last
longer? I will be putting a layer of gravel and some cement. Is there
a product such as cresote or tar that I can apply before I install the
frame?