Hi, I'm currently looking to do the same thing in a new build by adding a door between hallway and garage. I understand that I need to have an FD30 rated doorset with a self closer, however would like to seek some advice regarding the requirements for a threshold. In my case the garage floor is at the same level as the rest of the house and there is no fall present towards the up and over garage door. My initial interpretation after reading approved part B is that a 100mm threshold could be constructed between the hallway and garage to meet the requirements, it seems from what has already been mentioned above that there is some agreement with this? If so how do you usually go about creating the threshold? I assume that this would mean that the FD30 doorset would need to be fitted 100mm higher than any other doorframes in the hallway, are there any alternative ways to meet the requirements in this situation?