MF plasterboard ceiling - single sided

[Ron]

I have looked at the white guide and knauff guide at MF fire rated ceilings and there is lots of info.  However, I am trying to establish what fire resistance would be offered by a non fire rated 12.5mm plasterboard on a metal frame ceiling.  The MF is plasterboarded is on the lower side only and there is no risk in the void above.  I appreciate MF ceilings need various spacings for supports and hangers etc.  The plasterboard has no markings for manufacture.  Does anyone no where there is test data for such single sided  plaster boarded ceilings of any thickness (with 3mm skim).  Clearly it will be less than 30 minutes fire resistance but I am wondering if it would afford say 15 to 20 minutes which would allow time for persons to be evacuated from their bedrooms and adjoining corridor to a true FR30 compartment as a place of comparative safety.  A fire in the bedroom would need to spread through the single sided 12.5mm plasterboard MF ceiling, over the non full height partition to the corridor and pass through the corridor ceiling from the metal frame side to affect persons therein.  All ceiling penetrations would be FR30 rated.  Ideally the corridor should be a proper protected FR30 corridor but I am looking to see if I can find any information to make an informed calculation as to what fire resistance will be offered to the escape corridor.  From that point the Available Safe Escape Time can be gauged and from evidenced realistic fire scenarios an informed decision can be made as to whether the Required Safe Escape Time can be met (with a suitable safety margin).  Any pointers would be appreciated - I guess the major manufacturers of plaster boards do not give out BS476 FR test results on all plasterboards.  I assume to have such a test carried out as a one off would cost thousands of pounds.  Any help would be appreciated.  Thanks

[Tom Sutton]

I think because fire safety in not a science but based on assessment I have never seen a a guide that gives precise reading in minutes for fire resistance they all have used standard levels of FR (30.60,90,120, 240) and in the early days it just referred to the thickness of plaster board/skimming with no test evidence.