Replacing an Interior Garage Door

Hi

I need to replace an interior door from a garage into the house (utility room).

My understanding is that it needs:

- a step up into the room to prevent burning liquids running under into from the garage
- a 30 minute rated fire door, correctly fitted (frame etc)
- a closer
- thumbturn locks

Correct? What have I missed under building regs? Couldn't find an exact thread on this.

Cheers

 

Thanks - surely the 150mm only applies to new doors/garages, though? Not replacements - or that would effectively mean lowering the garage floor.