Screed on timber subfloor

I want to lay LVT onto a converted garage floor. Existing sub floor after carpet removed is timber with a little bit of concrete where doorway is. One flooring person said ply needs to be laid and screed the concrete part up to it, but another person said just screed it with Ardex na. My question is can you screed on a timber sub floor as I don't understand why I'm getting two different opinions.

 

Old garage floor you say?
I would be testing that for moisture, chipboard looks damp

 

Its not damp at all, was converted 5 years ago or so and was carpeted before, no issues there. Think its just the way the picture looks.

 

Would need plyed. And for the size of the concrete patch I’d use a repair mortar like A45 and feather it in. You wouldn’t know if it was damp or not without testing it

 

I’m guessing that floors floated NOT FIXED so levelling compound probably not the best idea. You may get away with a thin coat of NA

 

Will need plying out first. Can’t you just ply it?

 

No way you can NA straight on to that

 

Is it flat. If so just plywood it.