In article ,
Glen Able wrote:

From my browsing, it certainly seems that the majority of sources seem to
think that concrete is somehow the 'proper way' to do things, but I've not
seen anything to convince me it's actually necessary.

It isn't. It isn't even desirable when you want to plant climbers
to grow up the posts.

Having thought about the mechanics of it, I guess you can't simply say that
soil can't hold a post firm, because even if you concrete the whole thing,
you're effectively just making the post fatter and then relying on the
surrounding soil to hold it - although the increased size would mean you'd
be putting less pressure on the soil.

Yup.

If you do just pack the hole with soil, won't it be a bit weak near the
surface where the soil can easily move outwards? Which might let the post
start to wobble, even if it is held firmly at the bottom. Is this why you
suggest a concrete 'collar', or is that intended to keep water off?

Yup. With no collar, you need to embed the post slightly deeper.

Keeping the water off is fairly marginal, because most places in the
UK have 4 months when everything at soil level is effectively saturated
yet it is warm enough for fungi and bacteria to thrive. That is when
you really need the timber treatment. Keeping water off the top is
more valuable, because you can stop it running into the end grain.

I don't know of any proper experiments to see if it helps - some
people think that it does, and others disagree.


Regards,
Nick Maclaren.