On Tue, 18 Jan 2011 10:26:26 +0000, Chris J Dixon
wrote:

Jake wrote:

As you're clearly going for the "posts buried in the ground" approach
(I would use Metposts), please make sure that the concrete around the
posts is a bit proud of the ground surface and slopes down towards the
ground level all around the posts so you don't get any water
collecting around the bottom of the posts. When I bought my current
house (from new) the concrete was "underground". The original 4" posts
failed at ground level within 5 years. Twenty plus years later, the
replacement 3" posts (mounted in Metpost spikes) are still doing their
job and are still sound).

How easy have you found it to drive the Metposts whilst
maintaining their alignment?

I used some to secure an arbour. I had planned to anchor all four
legs, but after trouble with stones, I made do with two, which
has proved perfectly adequate. As it is a structure, and I had to
pack out the Metposts which were large for the timber, alignment
wasn't too critical. For 6 foot fence posts, there doesn't seem
to be any leeway.

Chris

I make a pilot hole first using a metal pole (actually a fireman's
wrecking bar) which gets me past any stones. Then provided you use the
right size driving block - don't use a 3" block in a 4" spike - it's
straightforward. I drive the first foot into the ground and then make
sure it's upright, drive another few inches and check again. From then
on in it'll go in straight. If the ground is a bit soft, you can dig
out some soil around the spike and put some concrete in for added
stability. Some people dig a hole as if they're sinking the post into
the ground, then fill it with concrete and drop in the metpost spike.
This is the best of both worlds - you have the strong fixing of the
concrete but the wooden post is still entirely above ground level and
so unlikely to rot.