aemeijers wrote:
"jJim McLaughlin" wrote in message
. ..

JoeSpareBedroom wrote:

I need to install three 4x4 posts to support grape vines. There'll be
some sort of wire stretched horizontally between the posts, as done at
vineyards. However, I'd prefer NOT to pour cement. Reason: This project
could be a total failure if the deer decide grape vines=salad. They ate
my neighbor's car last week, so anything's possible. So, if I'm using 8
foot posts, should 3 feet under the ground be sufficient?

I replaced some fence posts last fall. Pacific NW area, lots of rain,
relatively little freezing here on the vallry floor. Mountais are
different.
They were 4" x 4" PT in concrete, about 20 - 25 years in the
ground, rotted through in the 2 - 4 inches immediately above the concrete.
Getting the concrete outwas a pain.

Had the use of a neighbor's clamshell / post hole digger. Dug the
hole 3 feet deep. Put in 1 foot of crushed gravel, tamped and packed.
Placed post 2 feet into hole, tamped and packed gravel into hole up
to surface. Have 6 feet of post above ground. Looks good and
is very sturdy. From what i've seen around here, concrete
and 4" x 4" wood posts just don't work well together.


Were the bottoms of the rotted out posts completely surrounded by concrete?
I have found that is the usual culprit for rotted bases- the bottom of post
never drains, since it is sitting in a pocket. I've had good luck using
gravel in hole like you describe, but with the top six inches or foot in
concrete, to stiffen things up. (wood or metal clothesline poles.)

aem sends...



Old posts were set two feet into ground, bases resting on bare dirt (well,
mostly clay, wet soggy clay, but you get the picture.) About 1 foot of
concrete.
Old posts below the bottom of the concrete "plug" were deteriorated, but
not rotted out. It was the two inches to four inches of old post above the
"plug", plus about 3 - 4 inches of old post that were right inside the
"top" of the
concrete "plug" that rotted out. I hope I'm explaining that in a coherent
way. g.

I think the "plug" had a small space between its inner surface and the outer
surface of the post, as the wood dried and shrank. I expect that water
flowed
into that gap over the years and just sat there, puddled, and rotted the
wood.