We recently purchased a "new build" converted flat and observed that the gaps at the head and non-hinge side jamb of the FD30s flat front door exceeded 4mm. To remedy that the developer's joinery contractor has adjusted the head and non-hinge side jamb to close the gap, and included some packers to adjust the door hanging. The gaps are now under 4mm all round.

Our concern is how to remedy what we (are now presuming) is an increased gap between the frame and the wall. We are not aware of the developer having done anything other than to cosmetically deal with the gap between the wall and the frame At its widest point, I suspect these gaps are around 10mm. There is architrave on one side of the door (in the communal area) and no architrave on the inside of the door (flat side).

The developer can be a bit painful and so we are looking at how best to resolve this ourselves.   

The gap between the door frame and surrounding wall should be sealed in accordance with the requirements of BS 8214: 2016 Timber-based Fire Door Assemblies - Code of practice.  Use non-combustible materials such as mineral fibre & intumescent mastic to seal the gap(s) and consult a specialist where necessary.