Do door frames need to be filled?
Its alarming how many door installers/builders don’t know these basic facts!
Since 2005, laboratory test reports for 1 and 2 hour fire doors and the ABC/NCC standards have included a radiant heat test requiring that the build of the doorset will keep the safe side surface at less than 200C for 30 minutes*. This applies to both the door and the door frame/jamb.
The door builds satisfy this test as part of their standard build criteria, however, for the frame to pass this test, it must be core filled or back filled with either mortar, strips of FR plaster or wet plaster.
This filling is to create mass that absorbs the heat out of the steel door frame, its to prevent radiant heat from causing the surface temperature of the architrave part of the frame on the safe side to increase more than 180C above starting temperature.
Surface temperature above 200C can/will cause spontaneous combustion of materials on the side of the door being shielded from the fire. This defeats the purpose of a fire rated door!
With a fully involved fire the other side of the door set generating heat between 800 to 1000C, the insulating of the jamb may also make it possible for a person to take refuge in area beside the safe side of the door without the temperature exceeding 70C within 30 minutes.
This may mean the difference between life and death for the occupant of the room!