We've started going down the path of getting a volume builder to do a knockdown-rebuild of our current house in the northern suburbs of Melbourne.
However, I'm quite stressed about a number of factors regarding the build that I'd love to get feedback about.
- Builder only uses waffle slabs which I've heard is potentially problematic unless proper drainage is maintained and a path is constructed around the slab to move water away from the foundations. It seems that most volume builders will do waffle slabs.
- The soil tests came back as H2 (classed as P due to the existing dwelling). Builder sales staff said that the engineers will design the slab in accordance with the soil tests (though I'm unsure whether this will be overengineered or just to minimum standards)
- The block has a front to back slope (down away from the street) of approximately 1m so cut and fill will be required to get a flat building surface. This will mean our house will be slightly lower than street level (assuming the slab will ultimately raise the floor level of the house ~40cm)
- The current plan has the garage going up to the boundary - but how can proper drainage be maintained against the slab in these situation? I'm concerned we'd end up with run-off from the neighbors driveway pooling against the garage.
My key questions are:
- Should I be concerned about this build?
- How should drainage be configured on a sloping block?
- Should I move the garage away from the boundary to ensure that I can add concrete paths around that side?
- Has the AS 2870-2011 revision of the Slabs and Footings standard improved the situation/concerns with waffles?
Our current house is nearly 50 years old with nearly no visible movement and my concern is that we'll invest signficantly in this only to have issues down the track.