On 12/06/2018 08:42, fred wrote:
Dig 300mm square hols 700m deep for each support ? 28 inches deep ? Really? Sounds excessive to me.

Depends on the ground.

The footings for my new man cave go down 4ft. For a timber framed
building. The ground is sort of soft and wet and clay... for piled
houses AIUI they just push until they can't get it to go in any more.

Our old house was on sand, and I put a patio down just by levelling the
ground. It was still OK after 10 years.

Andy