Hello.

Currently working on residential property which require remedial works to the doors including lippings/frame adjustments. 
 

In some cases we’ve need to add a lipping to the head of the doors 8mm hardwood, Glued and pinned is this acceptable? We’ve done this including lipping bottoms to reduce gaps without causing to much damage to the frame works and property.

These are non certified doors obviously due to the age and works being carried out. 

When repairing fire doors, fitting a hardwood lipping can be an effective method to repair a damaged edge or to achieve compliant door leaf to door frame gaps. 

However, it is likely that such repairs would affect the manufacturer's certification for the fire door.  Can the manufacturer be identified so as to try and retain fire resistance performance certification, or is the manufacturer unknown?  If unknown, can the door's fire rating be confirmed?

Important considerations include: use of suitable adhesives, timber density and dimensions and of course the quality of the work. It would be advisable to undertake suitable fire door training and/or consult a specialist when undertaking these types of repairs.