Is 20mm adequate for a fire door lining?

[redhexagonal]

I just had a couple of fire door linings replaced as they were not deep enough after I overboarded the stud wall they are set in. The original linings were made with 30mm thick timber, and I only realised this evening that the new linings are made of 20mm thick timber. One of the doors was also replaced with a heavier fire door , about 45kg. The frames seem sturdy and the doors close fine, but I’m concerned 20mm isn’t thick enough long term for such heavy doors. Also there is now a 4cm gap on one side of the doors filled with foam which doesn’t seem very fire safe…. What do you think?

 

[^woody^]

I think you should get the firm back to rectify it.

 

[redhexagonal]

I think you should get the firm back to rectify it.

What do you think I should I ask them to do though? I can't find any mandatory measurements or requirements for fire door linings

 

[Deleted member 174758]

20mm is too thin. FD30 spec calls for 450kg/m3 density material (softwood or hardwood - MDF is a different spec) with a minimum thickness of 32mm (excluding stop) for single acting doors. Minimum frame depth is 70mm and minimum stop thickness is 12mm. Also the door needs to have a gap around the three sides between the door and the casing/lining of 2 to 4mm (checked with a gauge) and no more than 4mm at any point along the bottom when the door is closed, or failing that have an automatic drop seal fitted to make the door comply. Filling gaps with foam, even AFFF foam, is generally frowned on nowadays - current requirement is that smaller gaps are filled with fire mastic, larger ones (more than 5 to 10mm) with mineral wool. This info used to be on the BWF and CertFire websites

Over time, with a heavy fire door, a thin casing/lining can also warp meaning that the door will start to jam or ground eventually

Get them back - they have done a sub-standard job