Duplex = Double Brick?

Hi all,

Do all duplex houses have double brick for common wall?
The re agent told me so as to follow with fire regulation that a house must be fireproof for at least 4 hours before it goes to the next house.
It makes sense to me but how do you know for sure that common wall is double brick?
And when I knock on the wall it sounded like plasterboard.
My main concern here is the sound proofing from the neighbour.
Get up in the man hole and have a look that'll give you the answer. From what I see around the traps most people are using partiboard or something similar. Not real sure of ratings but I did hear the builder getting up the chippies for putting it on back to back which would double its rating from what I over heard so they pulled one side of it off and placed that between the next unit. Im not much help but heard talk of 60/60/60 with one sheet.
I was recently getting quotes for a duplex and a builder told me sound wise it was better to build with a dividing wall of single besa block filled with cement. My common sense told me that double brick with a cavity would better reduce sound. I can only assume it would have been cheaper for the builder to do the besa block full of cement trick. I bet he didn't even plan to fill them up.
Watched a duplex built recently that appeared to have gyprock as the common wall. No doubt this would have been double or even triple layered to give the required hours rating.

yep all true , it goes somthing like this , 60 mins to get out, 60 mins to put the fire out or response time , and 60 mins for the home to be unsafe to enter for the fire department, hence 60/60/60 ruling , others are 30/60/30 etc etc ..

so the home does not specifically have to be dbl brick, it can be plaster but must hace overlapped joins, this ruling also effects the other structual parts of a home , such as joists, bearers, and rafters, these items all have a fire rating , not that they dont burn, just that they may take 60 minutes to be structually un sound, ;)