Tim Lamb wrote:

I'm no expert but... a chap who does odd bits of groundwork for me
specialises in underpinning work for the insurance companies. We were
discussing how to go about creating concrete pads to support a steel
portal frame inside my timber barn. The architects have drawn a fancy
Acrow propping arrangement to take the load off the foundations. He said
this is unnecessary as most of his work is done by simply undermining
the foundations in 1m blocks and back filling with poured concrete.
Apparently the jobs sometimes require rammed dry mix for the 2" or so
actually in contact with the original foundation. Cue Huge:-)

A mate of min used to do similar stuff - often with angered piles to pin
the resulting concrete beams in place. Apparently they would use the
same undermining hit and miss technique, then they would insert
disposable jacks to prop up the bits they had undermined. Then undermine
the rest. Make up some rebar cage forms ready for the concrete pour (if
piles were involved then these would be done first and their tops and
rebar would be integrated into the beams). Then pour the concrete. Once
that had gone off, slate or dry pack could be used to take up any
shrinkage (plus the jacks would still be in place obviously).

--
Cheers,

John.

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