Can I resize a fire doorset if it doesn't fit?
Resizing a doorset is not something that should be done without first contacting the manufacturer.
Most door designs rely on components being of a minimum size in order to perform in a fire.
Lippings, also known as door edges or foredges are particularly important on typical flush door leaves – removing 3 or 4 mm can in some instances halve the depth of a lipping which could have a detrimental effect on the fire performance.
The simple rule should be that if the door is sticking and needs a very small adjustment of 1mm or so then this should have no detrimental effect on the doors performance for fire resistance.