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Nominal Fire Doors - Check as FD30 and/ or FD30S

Guest Gary

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I live in a communal development of flats which was built in 2004. 

There are 20 apartments with private entrance doors accessed via a shared hallway. There are also 25 communal doors (a combination of internal doors and storage/ riser cupboard doors). The apartments are split over three small low-rise blocks. 

A Fire Door Inspector recently assessed the fire doors as ‘Nominal’ as they are unlabelled. In his opinion, they are of good quality and in excellent condition. 

As these doors are serving a private development, with access via communal corridors, I understand that they should meet FD30S level (i.e. Fire AND Smoke). The Fire Inspector’s report shows the doors meeting this standard on his final report, but many of the threshold gaps are greater than 3mm. As such, they wouldn’t meet FD30S requirements (3mm on all four edges). However, it could be such that Normal Fire Doors are never tested to this level, and only have a checked to FD30 status (3mm on top, left and right, and 10mm on the threshold/ bottom edge). 

I have read the very informative report on Nominal Fire Doors on your website, but cannot determine whether my thinking, as explained above, is correct. 

I have read the very informative report on ‘Nominal Doors’ on your website, but cannot determine whether my FD30 vs FD30S considerations, as explained above, is correct. 

I’m confused as to what the maximum edge gaps can be based on a combination of nominal doors and requiring smoke protection as well as fire. Please can you advise whether we should add on an extra requirement to the Fire Inspector’s report to ensure that the threshold gap doesn’t exceed 3mm. Then, I can instruct the corrective work with our carpenter. 

Thank you, in advance, for your help. 


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The fire doors should comply with BS 8214: 2016 in terms of their FD30(s) status.

Door leaf to door frame gaps should be 2mm to 4mm for best performance.  Smoke seals must be effective, the brush, blade or fin should close the gap but not impede the self-closing action.

Threshold gap should be 3mm max or where this is not possible the gap should be 10mm max between the bottom edge of the door leaf and the floor. It may be possible to fit a flexible seal / threshold plate to close the gap in the door-closed position.  The seal must not cause the door to bind on the floor and so impede the self-closing action.

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Thank you for your reply, Neil.

Are you saying that a Nominal Fire Door can still be categorised as FD30S? If so, would I simply need to follow the additional requirement of reducing the FD30 threshold limit from a maximum of 10mm to a FD30S threshold limit of between 2mm and 4mm?

YouI also say that if it’s not possible to have such a small gap, then we can utilise up to 10mm at the threshold. If this is the case, does this mean that fire door would no longer be FD30S and only achieve FD30?

Please forgive my naivety, but I am simply a resident in a development of flats who wants to do the right thing. Our recent Fire Door Inspection said that all of the thresholds were okay, but some of them are actually much more than 4mm, so I’m considering adding an additional requirement for all of our owners to reduce the gaps where needed.

Thanks, once again.


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In order for a timber-based fire door to meet FD30(s) status:

A) The gap at the threshold should be 3mm maximum


B) The gap at the threshold should be 10mm max and with a flexible seal installed to seal the gap under the door, in the door-closed position. The seal must not cause the door to bind on the floor and so impede the self-closing action.

Reference: BS 8214: 2016 Timber-based fire door assemblies - Code of practice. But applied in the context of the fire door being 'Nominal'.

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