Very helpful, Thank You.
One more thing, when adjusting doors to achieve the 3mm gap on an fd30 door, 10 years old, that has no intumisent hinge packers should we be removing the door and the 3 hinges, removing extra material from the frame and door recesses to allow for the thickness of the hinge packers, refix the hinges to the door, Then rehang the door .
Or can we put an odd hinge packer behind hinges on frame side to adjust the door.
Thanks