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Fire door trimming

Guest YanS

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We have just recently bought FD30 doors which we have had installed in. Due to the size of the door openings and unlevelled walls the builder had to trim them all. Does anyone know what is the maximum amount that you can trim a fire door? Once trimmed what paint needs to be applied to seal the door if any? Has anyone ever used an intumescent paint and any brand you would advise? Besides, what is the maximum space allowed between the door and the floor?

Thank you

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Hi YanS,

The trim allowance depends on the type of fire door and this information is usually included on the installation instructions that come with each door.  If you can find a label on the top edge of the door you should be able to trace the manufacturer and data sheet to find out the maximum trim allowances.

Where it is necessary to trim doors excessively fire door blanks are available for this purpose. The threshold gap should be 3mm maximum for a fire door that is required to restrict cold smoke spread (this will apply to most fire doors) or where restricted cold smoke spread is not a requirement you should refer to the installation instructions or data sheet.

It is not necessary to use intumescent paint, usual water based or solvent based paints are OK to use.

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Due to the restricted size of the door frames there are no fire doors in that size. The manufacturer states that they shouldn't be cut more than 3mm from each side however they had to be cut more than that in order to fit in the door frame. In another post there was a suggestion that you can get a fire strip or intumescent paint to seal the trimmed area. Does that sound reasonable?

I've seen intumescent paint that will make a normal door into an FD30 fire door, does this work?

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You can get bespoke fire doors and they use a blank and construct  the fire door using it and using intumescent strip or paint will not solve your problem, it is only a possibility in very rare situations where there is no alternative available. Check out https://www.safelincs.co.uk/custom-30-and-60-minute-fire-doors-fd30-fd60/ it may help.

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