Site issues in building investment property – advice please!

Hi all,

we are building an investment property and are having issues with the builder regarding the garage wall on the boundary line.

The site cut next door was deeper than first thought as its a new estate.  However, the builder didn't tell us  of any problems, they just made it sound like there was an issue with the retaining wall next door.   the cut was there BEFORE our builder started on the house.  Our house is now at lock up stage.

The upshot is that we found out that the garage wall is sound only as long as a dirt batter on the neighbors property stays in place!

The building surveyor, engineer (all working for the builder) are playing with words, they say that the wall is sound, so long as the batter stays in place.  We are not happy with this as we feel that our home should stand on its own foundations!

Builder is quoting clause 12.1.2,of the building contract, saying they can pass any additional costs to the clients,
They are saying they are willing to go half's with us in underpinning the property.  Given that if we had known about the problem at the beginning bored piers would have cost about $1,000.

I have phoned various departments and am following procedure, but would appreciate your thoughts. We feel that it's ridiculous to rely on the neighbors good will to hold up our wall!  What's the law on this?

Thanks.