Well, for the base that sits below the deck, I was thinking about making
up a steel plate, 450 x 450 x 16, with pedestal legs a couple of inches
high, bolted in to the rock. I thought this was fine, but I got talking to a
friend who loves to over-engineer things (he's a big boy and his hobby is
earth moving equipment) and he talked me in to drilling a hole and sinking
a post in the rock. The post would then have a pipe flange welded to the
top, and the pier itself would have a matching flange, the two then would
bolt together.
We agreed that a bigger diameter is better, so decided on a 250mm
(10 inch) post and pier would be ideal.
We searched around for a suitable piece of 10 inch pipe to make this
from, but it's not that easy to get 1.5 - 2 metres of it. Then we realised
that I already had the perfect piece back in my Grandmothers shed!
That sorted, off we went to Kennards and hired a core drill, stand,
extensions, and a 250mm core bit.
This not unsubstantial bit of kit has to be bolted down for use, so we
drilled and set a loxin into the rock, and tied the drill stand down with
a length of threaded bar.
Here it all is, bolted down and ready to bore:
Water and power were turned on, and away we went. Boring the hole
went quite easily, and before too long we had bottomed (topped?) out
the bit, and had to get the first plug out of the hole. We did this by
setting an eyelet into the top, then driving a cold chisel down the cut.
The plug broke away at the bottom, and we lifted the first section out:
Next we added the second extension and continued down the hole:
