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Intumescent strips

Guest Steve

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Good afternoon all,

with regards to intumescent strips, I know they can be installed within the door frame or the door, but is it acceptable to have them in both, on the same door set, as I assume both will expand when subjected to heat.

also what if the strip was missing from either the door or the frame, would it then be acceptable just to fit a strip where it is missing or would the door set require replacing. Many thanks. 


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If an intumescent strip is missing from the edge of the door leaf or from the head or jamb of the door frame, it should be replaced with the correct sized strip and of the same type as the other strips fitted.

The reason that intumescent strips are not fitted to both door leaf and frame, is that the intumescent strip is designed to expand to form a seal against a solid surface rather than against an opposing intumescent strip.  It is not uncommon to find intumescent strips fitted to both door and frame opposing each other and this has usually been done in ignorance of the fire door installation requirements. Some people often say that having strips fitted in this way could cause the doors to open in a fire situation due to the expanding pressure from both seals and therefore the door would fail to provide the required fire separation performance.  However, there are some double leaf fire doors with edge protectors that have been tested with opposing strips to the meeting edges of both door leaves. 

Clearly, a fire door fitted with intumescent strips in a manner contrary to the door manufacturer's installation requirements could behave in an unpredictable way in a fire situation, that's why the fire door industry trade associations go to such lengths to promote correct and compliant fire door installation.

More on this at https://www.ifsa.org.uk/ 

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