Building a new deck over concrete cancer

Hi,

Need some advise my back verandah is the old pebblecrete style and want to replace with timber decking. I live in the hillls district. The veranda appears to have concrete cancer a whole chuck of concrete fell off into my hands while I was inspecting under it (about a meter off the ground) and the whole thing makes me nervous thinking it will collapse one day.

Carpenter doesn't want to demolish and wants to build deck straight over saying should be right though I'm not keen. Rather have the whole thing demolished.

I'm also confused whether I need council approval I rang them and did not give me an answer just referred me to a website that I'm trying to figure out.

My questions:
Do I need council approval to demolish concrete veranda to put new timber decking?
Do I need council if I extend the deck making it wider to about 40sqm?
If I don't extend the width its under 25sqm do I still need approval if timber goes straight ontop? If concrete is inspected and repaired by professional with timber going straight over it?

This whole reno is turning out to be more complicated than I thought anyone has any thoughts? If I have to go through council anyone have any experiences? I wonder how long it will take and what's required I have no plans.

Did you find anything further out? I am in almost the exact same position minus the concrete cancer. I find it very hard to find out from Hills Council what is exempt, complying etc.

Hi I am now going through Australian Outdoor Living company that takes care of all the paperwork with council. It is more expensive though I don't have the time to go to council and do drawings etc..
It turns out I need "149 Certificate, DP Plans & 88B Instrument" they have submitted for me the DP is because of the gable design roof I chose and not flat roof. It doesn't make sense to me though I don't really need to..I just have to organise the demolishing the concrete part separate though it won't be hard to do that.
As if neighbours complain council could come over and say stop work and pull it all down. Also if you ever sell the house and not on plans that could cause issues too.
All the other small 1 companies the carpenters said you don't need to go through council suspect only because they can't project manage it all..

"do I need council approval to demolish concrete veranda to put new timber decking" No if it's the same size in appearance, 40sqm will need approval.

"Rather have the whole thing demolished" If the old verandah wasn't good enough to build over, I doubt the carpenter would risk it lasting 7 years. I'd get a couple more quotes if you're not happy.