Since I did't get a reply on my previous post - making a new one.
I was recently on a job where the joiner installed 45 mm doors in an area specified as FD30 on the plans. The supervisor is now insisting that they must be a minimum of 44 mm, otherwise the certification will fail. I had always assumed that both 44 mm and 45 mm were acceptable for 30-minute fire doors, so I’m quite confused.