I have been installing fire doors for a few years now and have always used an approved fire stopping sealant for 5-10mm gap and anything between 10-20mm have packed mineral wool tightly and capped with fire stopping sealant. If the gap was over 20mm then we would then look to do something to substrate for example for stud wall repair wall where possible. I know  blue 60 is on the market but I’m now seeing installers using a mastic that they say is up to 30mm (with mineral wool) is this an acceptable method for door frames? It’s not often this happens but on occasion the arch’s have not been removed by surveyor.

BS 8214: 2016 Timber-based Fire Door Assemblies - Code of Practice recommends 20mm as the maximum linear gap width, using mineral fibre and intumescent sealant.  Therefore, it would be necessary to refer to the specific evidence of fire resistance performance, using those materials and products, to support a gap of 30mm