In article ,
ks says...
On Wed, 19 Jan 2011 11:17:17 -0000, Charlie Pridham
wrote:
snip
I would say that it is a toss up whether the the metal post bottoms rust
out or the posts rot before 10 years are up I had replaced the 4x4"
tanalised wood posts on my large pergola 3 times in 27 years before I
gave up and built masonary posts with reinforced concrete cores
I know I live on the wetter side of the UK but the disruption to the
garden at each rebuild was very annoying and it worked out a lot cheaper
to build masonary in the end for the size of the posts

I can only repeat that I have Metposts that are 20+ years old and
they, and the posts in them, are perfectly sound (and as near
perfectly vertical as dammit save for one which was deliberately
skewed to get around a tree on the other side!). I had to replace some
fence panels that were damaged by wind last year but that's all. I
make sure that the bit of the spike that holds the post is above
ground - I've seen some driven right in and maybe that is why they
fail - rust at the weld between the spike itself and the "container"
on the top.

Cheers
Jake

I suspect the difference may be my very acidic soil conditions and almost
permantly wet ground, I went over to using them so that when the
tanilised posts rotted I could drop a new one in without disturbing the
ground and therefore the plants, but the failure rate has been too high
to want to use them again, over 10 years the spike is reduced to
nothing, and often the clamping point has gone by then as well. But I
agree its easy to get them upright and solid and I never had issues with
posts flopping or not being vertical, they are a lot easier and quicker
than digging post holes thats for sure!
--
Charlie Pridham, Gardening in Cornwall
www.roselandhouse.co.uk
Holders of national collections of Clematis viticella cultivars and
Lapageria rosea