Drainage Issues in New Unit

Hi all, found myself in a bit of a situation, so looking for a bit of assistance from the ozbargain community. Sorry, it's a bit long-winded.

I bought a brand new unit in Melbourne which settled in October last year (one of 4 on the subdivided lot)

in December I noticed some floorboards warping/cupping in the TV room along the sliding door to outside (east wall). So I contacted the builders who came out and silicone'd the door from the outside and said to let the moisture dry a bit before they would pull up the floors.

Almost 2 months later the flooring guys come out and pull up the floorboards. There were visible signs of water getting in along the sliding door wall, which we expected, but there were also signs of water getting in along the north wall. These marks extend in about a foot from the wall. The flooring guy suggested to wait 2 weeks to see if the moisture would dry out.

In April the builder came out again and silicone'd the sliding door from the inside. He suspected the water coming in along the north wall could have been either from the roof and getting down into the floor, or coming up into the slab from the outside ground, so he flattened the path outside along the north wall to try to drain the water away from the house (we had noticed water pooling here previously).

It rained heavily the weekend after the builder came out. That week, the flooring guy came out again and tested the moisture in the floor. It was off the chart on his meter - he suggested waiting another 2 weeks and using fans to help dry out the slab. On the same day the plumber who plumbed the house came out for unrelated work, and we discussed the possibility of installing an aggie pipe - which he said was not done during construction, but would not be hard to do. This must have got back to the builder's bosses because we got an email later that night saying:

"(the site manager) has arranged for the flooring to be rectified and plumber has attended. There was no requirement for us or documented on the drawings to install an aggi pipe for the location you refer to. For us to organize for the installation of aggi pipe would be $1980 plus gst"

At this point we're getting frustrated so we replied "water is getting into our slab, how do you propose to fix it?"

His reply "That component has been rectified water was getting under the sliding doors as it was not sealed properly and the drain holes on the sliding door track were blocked. Thats how the water got under the floor boards.” (mind you, he has not visited the property once, and his builder had previously expressed thoughts that water may have been getting in from elsewhere).

We emailed back to that and told him that the sliding door had been sealed up for over 2 months, and that the subfloor was still far too wet along the north and east walls. We concluded with "After 2 months from our initial conversation about the damage, we still have no resolution. What do you suggest to do to rectify the north wall water damage?"

That last email was sent about a week and a half ago - we haven't got a reply.

The flooring guys came out again today and tested the moisture - still off the charts on their meters. Told us to keep running the fans and let the moisture dry out.

We're convinced that the water is getting in due to poor drainage on the North wall.

I guess I would just like to ask peoples' thoughts on the situation and what I should do next. Should I pursue the builder to install an aggie pipe at their cost? Is he obligated to fix the drainage issues? Or am I sweet out of luck and have to cough up the costs myself?

Any and all help is much appreciated.