Fire door with no intumescent seals — can it be retrofitted?

The two seals do different jobs

An intumescent strip is inert at room temperature and expands rapidly once heated, sealing the perimeter gap against flame and hot gases. A cold smoke seal — usually a brush or fin, often combined into the same carrier — works from the moment the door closes and restricts the movement of cool smoke, which is what actually travels down an escape corridor first.

A door needing both and fitted with only an intumescent strip is a partial solution.

Is it actually a fire door?

Before discussing seals, we establish whether the leaf is certified. Indicators include a label or plug on the top or hanging edge, a solid dense core, the correct thickness for its rating, three hinges, and a frame with the correct stop depth. Where none of that is present, the honest position is that the opening needs a new door set rather than a retrofit.

When retrofit sealing is acceptable

Retrofit is a recognised option on certified leaves where the manufacturer or a tested retrofit system supports it. It has to be done to the specified groove dimensions, with a compatible product, and recorded. Done properly it is significantly cheaper than replacement and keeps original doors in service — which matters in older and listed buildings.

Recording the decision

Whichever route is taken, the reasoning belongs in your fire door records: what was found, what evidence there was of certification, what was fitted and to what specification. That is the difference between a defensible position and an argument.