Intumescent strips and smoke seals: what to look for
The strips around the edge of a fire door are what seal the gap in a fire. They are easy to damage and easy to paint over, and either one can stop them working.
Two jobs in one strip
An intumescent strip swells when it gets hot and seals the gap between the door and the frame. A smoke seal, usually a brush or a soft blade, stops cold smoke getting through before the heat arrives. The two are often combined in one strip, and it can be fitted in the edge of the door or in the frame.
Along the top and both sides
- A strip runs along the top and both sides, with no missing lengths
- It is firmly fixed, not loose or hanging away
- It has not been painted over
- Where there is a smoke seal, it touches the door edge or frame when the door is shut
- On a pair of doors, the strips where the two doors meet are in good order too
Government guidance for England notes that if a door was never fitted with seals, that may be acceptable, depending on what your fire risk assessment says.
Like for like, not any strip
A damaged or painted strip should be replaced with one of the right size and type for that door. A generic strip from a hardware shop may not match what the door was tested with. Photograph the fault with the date showing, so the record shows when it was found and when it was put right.
What people ask about strips and seals
Can you paint over intumescent strips?
No. Government guidance for England says to check that strips and seals have not been painted over during decorating. Mask them when the door is painted, and replace any that have been painted.
Do all fire doors need smoke seals?
Not always. The guidance says a door without seals may be acceptable, subject to the findings of the fire risk assessment, so check what yours says.
Do the strips go on the door or the frame?
Either. They can be fitted in the edge of the door or in the frame, and they are normally combined with the smoke seal in one strip.
Check your doors now
Door by Door is our free fire door check. Walk round with your phone, answer the checks at each door and add photos of anything wrong. You get a dated report by email to file, or to forward to whoever fixes it.
A plain summary, not legal advice
This guide follows the rules in England. Wales shares the Fire Safety Order but not the 2022 England regulations, and Scotland and Northern Ireland have their own fire safety law. Your fire risk assessment is the place that says what applies to your building, and a self check never replaces a fire door inspection by a competent person.
We put fire doors right across County Durham, Teesside and Tyne and Wear. If you are further away, a dated report from Door by Door is exactly what a local fire door specialist will want to see.
Tell us where to start
Ring Wayne Cator, our Managing Director, or send us the details and we will come back to you.