Quote:
Originally Posted by glend
Well if you have sandstone below the surface, you can look at using that as part of the footing. Dig down as far as you can, and then use a hammer drill to bore some holes in the sandstone. Get some short rebar lengths from Bunnings, using an angle grinder cut it down to maybe 200 or 300mm in length, put some good construction epoxy on one end and drive it into the sandstone. Don't use the cheap 5min epoxy, that stuff is hydroscopic and will break down if constantly wet. Now you can pour your footing over the sandstone porcupine, and it will be fine.
Typically footing dimensions can vary from 0.7m x 0.7m x 0.7m to a full cubic metre depending on your subsurface and rock etc. There was a thread on the Cloud Nights forum about a guy building on rock, and he just put the footing right on the rock. My footing is on clay and conglomerate, and I just hammered in some galvanised angle iron, once my back said enough of this digging. You will likely get all sorts of opinions on this topic, but there are no absolutes.
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Absolutely better using the existing rock
