Duplex - estimated cost and party wall

Hi guys,

I have been looking at some duplex type properties and would like to know if anyone has any feedback on the below 2 items.

Common/party wall

According to the dwelling plan the party wall is 270mm (Imgur). We were also told that it was an insulated double brick rendered party wall (50mm gap) which allows maximum sound proofing as well as fire protection.

With these specs does that means the party wall is absolutely sound proof?

I’m trying to understand if this wall is below/above average quality and if not completely sound proof what sort of sound could still go through? Neighbour talking, watching tv, listening to music, etc.

Estimated cost

The council DA tracker provides an estimated cost for a development application and I have seen huge discrepancies between similar type of properties (duplex with no pool). One could be $600k and another one $1M.

I understand that costs can differ based on quality of material used, etc.

Is it possible that the estimated cost doesn't include everything for one developement vs another one?

For example the one costing $600k only include the actual construction work whereas the one that cost $1M also reported appliances, light fitting, fixtures, etc.

Thanks.

 

2 x 110 mm brick + 50mm gap + 2 x 10mm render. Where's the insulation? It complies with the fire rating and the sound transmission requirements.