Large gaps under fire doors

[Guest Mark Norris]

I am working on a large industrial building

Which has more than a 100 fire doors; parts of the building are over 150 years old  

I have been asked to upgrade the fire doors ,many will need new doors sets  and others will require retro fit upgrades ,the problem I have is that many of the doors have large gaps under them, some up to 25 mm this is to accommodate the  uneven slope of the floors so that the doors will open . I note that there are now drop down threshold seals but they seem only to accommodate gaps up to a 14mm  

 I could cock the hinges to help raise some of the door but I doubt this would be sufficient .

Because many of the routes are used by ped trucks it’s unlikely that I could use threshold cills .

I am sure that many a joiner has come across this problem in the past,

 is there anyone out there who can advise how to overcome this problem or advise of  a product that will.

I contacted the local BI for advice but he was decidedly unhelpful

Regards Mark Norris

[Neil Ashdown MAFDI]

The requirement in terms of threshold gap for a timber based fire door is 3mm max where the door also provides restricted smoke spread.  Where restricted smoke spread is not a requirement the max gap is nominally 10mm (sometimes less depending on test evidence).

More than 100 is a lot of fire doors (for an industrial premises) so one would ask whether they all really need to provide fire and smoke separation?

The building operator should have carried out a fire risk assessment and should carry our periodic fire evacuation drills. From having conducted those a fire strategy document should be available and if it contains sufficient information it should provide details of the locations and ratings of the fire doors.

Once you have established which doors are necessary to the fire strategy you will need reference documentation on which to base your upgrading works.  A good start would be these two:

BS 8214:2016 Timber-based fire door assemblies - Code of practice  https://shop.bsigroup.com/ProductDetail?pid=000000000030332501    and Code of practice, Hardware for fire & escape doors http://firecode.org.uk/Code_of_Practice_hardware_for_fire_and_escape_doors.pdf

[Tom Sutton]

Other guidance documents for someone dealing with fire doors is https://www.asdma.com/knowledge-centre/ I think it is worth checking them out.