I have recently carried out a fire door inspection on a building. I have found that a fair percentage of them have bowed or twisted to varying degrees. Could anyone twell me what the maximum permitted bow or twist is? On some of the unequal pairs, the step between the two is up to 6mm at the bottom and I have failed them as a result, but some are only 3-4mm and I am on the fence on what I should do with them.

In terms of fire resistance performance documentation from the manufacturer, generally the door leaf should not stand proud of the door frame (or other leaf in a pair) by more than 1mm. Some door certification documents state no tolerance at all.  

It will be necessary to assess how critical these defects could be given the safety risk at the particular location(s) within the building. 

Thank you Neil. We are only inspecting the core doors in the office blocks, so stairwells and risers. They are all critical doors. I have a meeting with them on Thursday to discuss their options which are not looking great!!!