Gaps under doors for MVHR and comparability with fire regs

[joe90]

You may find this interesting. https://www.safelincs.co.uk/use-of-existing-fire-door-frames/

[saveasteading]

3 hours ago, Adsibob said:

This would suggest my architect is

A bit extreme and better implied than said.

 

It is perfectly possible to make a fireproof door this other way, but it is much easier to convince the BCO of the standard ways.

Whether this is  careless or a way round an issue I can't say, without seeing it.