Extending weatherboards

Hi,

Can anyone point me to any threads on extending weatherboards?

Im curious to know what is possible i.e extending 2 stories or single story?
Speed at which an extension can be completed?
And of course cost.

If for example i was looking at the potential in adding a 3rd bedroom + rumpus to this property.
http://www.domain.com.au/Property/For-Sale/House/NSW/Caringbah/?adid=2008340017

would it need to be on the same level? Would you have any idea for estimating the cost?

Thanks.
 
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