I'm digging the footings for my conservatory, and the original drawing suggested digging down 600mm for a 600mm wide, 150mm strip footing, which i made the decision to make a minimum of 250mm. I got to 600mm and the ground was still soft. Incidentally, it is pure clay where i am..completely orange/red! I spoke to a friendly local surveyor who said i should go down to 1 metre which i have done. I then read that if you can drive a 50x50 post more than 6 inches into the ground that it is not firm enough...i tried this, and using a lump hammer i could get it at least 8 inches in...i didn't try any deeper for fear of not getting it back out!
So what do i do now?? Dig closer to australia, dig wider than the 600mm, add reinforcing to the strip, or trench fill? It seems an awfully deep trench for a 600mm high wall and i'm already down as deep as the footings for the main house.
Any advice greatly appreciated.