In article ,
David Hansen writes:
On Mon, 10 Nov 2008 16:56:20 +0000 someone who may be Dan Smithers
wrote this:-

I have just bought a lamp-post for my front garden to replace a small
pedestal that had been knocked over too many times.
I am planning to make a base for it to stand on using threaded rod and
angles buried in concrete.

1. how deep does it need to be?

2. Should I use stainless steel, or will mild be good enough for this
purpose?

3. How do I work out how much concrete to mix? considering that bags of
cement and ballast are sold by weight and holes in the ground are
measured by volume?

Not enough information.

How tall is this lamp post? What is it made of? What is attached to
what will be the top?

For streetlamps, typically they extend into the ground by around
15% of their height above ground, but they are sometimes set into
a vertical pipe which does effectively extend the depth. For a
relatively short column which you probably have, this figure
probably needs to be more than 15%, as much of that will just be
in the topsoil which won't provide much of a foundation.

Many years ago, I saw the contractor's spec for lining a long drive
with gaslamp style electric lighting. These were done by setting
a length of fat pipe vertically, well below ground level in concrete.
Pipe hole left empty. When this was set, the lamp column is stood
in it, packed in with mortar with almost no cement in it (I think
this it to allow it to be pulled out if it has to be replaced).
The bit which I particularly liked was that the columns had to be
set randomly a few degrees off-vertical, but never towards the road.
In the picture of the final result, it looked like a road with
gaslamp columns which had been there for over 100 years. The
setting of them randomly slightly off-vertical was a very clever
design effect.

--
Andrew Gabriel
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