I have to raise my house 1.8m! is this even possibly True ?

I sent you a PM - check your messages.

Finished floor level which is the end height

I'm not technical, but Ryde Council has Flood Maps. They use to be on their website, but I can't seem to find them these days. I know they are available if you go in to Council and ask to see them. This shows whether your home is listed in a Flood Zone. About 20 years ago, there was a huge flood, especially around the Eastwood area and many homes are listed as flood prone. (1 in a 100 year flood). This is probably due to the fact that there were many creeks (in the old days) that our now concrete streets with no place for water to run off. I have heard of others in the area wanting to build in a flood zone and the requirements are quite large now. Many of those people have decided to "renovate" rather than rebuild due to those issues.