We've done some underpinning.
This was on clay/shale mix with some (but not much sand) thrown in. The bottom line is that the whole house should be standing on subsoil that expands and contracts at the same rate.
Basically our house was heaving in that the internal supports (brick veneer) were not in sink with the external walls such that things would rise and fall at different times depending in the moisture penetration.
We then decided to do an extension which meant that we needed to dig down to rock at the back of the house for the foundations. Our block has a 30-45 degree slope to the back. We had to dig down up to (down to
) 3 m to find rock and at the same time underpin the whole back wall. The rock goes deeper across the block such that it was only 1m at one end and 3m at the other end. It took 15 cubic m of concrete just to fill these holes.
The next job was to replace all the main internal supporting peers again digging down to rock 2-3m holes and another 15 cubic m of concrete top of with galv posts.
Obviously whilst you are digging the house/wall/floor still needs to be supported so we had to use some pretty heavy duty acrow props, jacks, massive blocks of wood and lengths of wood etc.
Finally we had the underpin the side of the house where the bearing rock was 3m+ down, another 14 cubic m as these holes need to be enormous to be able to dig them by hand.
We still have some more to do which will finally conclude our underpinning unless there is movement somewhere the engineer did not think would move.
I guess you would can this mass underpinning as it is simply digging under the foundations pouring in a lot of concrete and then finally grouting between the old and the new.
The Uretek system is basically used to fill and /or re inflate subsidence (as I understand it). Unfortunately did not apply to our problem as our issue was both shrinkage and expansion.
We could have used coils or piles but it is impossible to get any heavy equipment down to our house.
In the end you will need to speak to an engineer (the right type) who should asses what the fundamental problem is and design a methodology which best suits your site.
Cheers
PS we didall the underpinning ourselves as it would have cost a fortune to have a builder
