10.8 x 12 mt = small extension eh ???? Thats as big as my whole house. You will need to take your fully designed, detailed and approved plans to a truss and wall manufacturer. Google is the way to go. There are a few very large companies but also quite a few small guys who can be very competitive on price. People ( not me
)are dropping prices a bit at the moment aswell due to the housing slump in Brisbane