On Thursday, 14 March 2019 21:35:14 UTC, Andrew Gabriel wrote:
The recent winds have seen the end of a boarded arris rail fence.
The posts are 100mm x 100mm, 3m apart and the fence about 1.6m high with
3 arris rails per section. It was probably 30 years old.
The posts rotted off at ground level about 15 years ago, and I hammered
post sockets into the ground and lifted the posts with the panels
attached into the sockets (which was one hell of a job - they were damn
heavy). I think it did well to last another 15 years, but now both the
posts and arris rails have rotted, and I think that's it.

I intend on mounting the replacement posts so they stop above the
ground. One possibility is to reuse the post sockets, but the one I've
uncovered so far under the undergrowth and collapsed fence is no longer
vertical, so they may have had it too.

Another thought is to use concrete repair spurs set in concrete, with
the posts bolted to these. There are some repaired posts in the garden
like this already - they've been there 20+ years and and rock solid.

Any thoughts on concreting these in? I can't believe one bag of
postcrete is enough for a 1.6m high fence on 3m spaced posts.
Is postcrete a compromise over using a real cement mix?
If so, what's a good volume per post, and what concrete mix?

Also, is there a different name for arris rails which instead of being
flush with the post faces are mounted on the surface so the boarding is
spaced slightly away from the post faces? Instead of triangle section,
they are almost rectangular but the top surface is cut with a slight
slope to prevent water pooling. (This is what I would like to use and
have seen elsewhere, but not what the fence used before.)

TIA
Andrew Gabriel

In our last house, which only had a short fence, one post lasted without obvious damage while the rest all suffered right up to total failure. The one that lasted, I had made quite a large hole. Put fairly coarse gravel the bottom and made it dead flat and tamped down. Stood the post on the gravel and then filled the sides with concrete (might have been postcrete - far too long ago to remember). That meant any water could, eventually, drain away.

In our current house, the builder has done what looks like a fine job with every post wrapped in something that looks a bit like roofing felt to about four inches above ground. Only about three years old so not really tested.