Understanding fire doors is a complex subject, we often get asked by our landlords Can existing doors be upgraded to fire resistant standard?

An upgrade of existing non-fire doors to FD30 status is sometimes possible through using an intumescent varnish or paint, depending on the condition of the existing door.

Any unpainted doors could be coated with intumescent varnish or paint, to the manufacturer's/supplier's specifications creating a 30 minute fire resistance. A painted door could be covered with an intumescent membrane, either fireproof card/wood veneer facing, would be more aesthetically pleasing than plain, non-combustible board. If the door has glazing, the glass panel(s) must be replaced with a fire rated glass.

The upgraded door must be re-hung with at least three fire protected hinges, to prevent warping. The integrity of a fire door will be severely compromised if it should warp, as it will no longer fit snugly in its frame creating gaps. All other hardware, e.g. locks, latches, etc, must be similarly upgraded to fire resistant standard. Other modifications, including the addition of intumescent seals, will also be necessary. Some surface mounted fire door seals allow an upgrade without having to cut out a channel in the door to fit the seals.

Intumescent paint supplier can offer a long-lasting lifespan at reasonable prices.  This is a great alternative for your current doors to consider.

Fire doors should be made of solid timber, at least 44mm thick and with a sound frame that is capable of bearing the additional weight of the upgraded door. The gap between the door and the frame should be 2 to 4mm. If an old door does not meet these requirements it will need to be replaced

Due to the specialist nature of fire doors, it is always advisable to fit them from new, instead of trying to upgrade an existing door.

So, in answer to your question: Can existing doors be upgraded to fire resistant standard? The answer is Yes. However, do your homework first and if get certification once the works are complete, you may need to prove you had the work carried out at some point in the future.