30 min proof cabinets

I've been asked to quote for what are essentially fitted wardrobes at the local school, they need to be 30min fire safe, not something I really deal with so looking for best ways of construction.
They had a saftey inspector in and all he's said is that 6mm plasterboard is 30min proof, hasn't spec'd anything else.
I'm happy to use 12.5mm plasterboard for top and sides, but was thinking of fire retardant mdf for the doors? If the doors are overlayed is this enough to protect the framework if that were pse softwood? or other options for fireproofing the framework ie different material or clad softwood with the mdf?
Does intumescent strip need fitting to cupboard doors? These are for housing drama costumes mainly.

 

Yes was wondering that myself for same reason, if so then I'll go for fire retardant mdf all round.

 

Are boards sold as fire retardant and fire resistant completely different boards? some places just have it marked as FR, I get that as you say retardant and resistant are two different things but at least on line stockists seem to use it interchangeably.
Anyway, quoted based on a carcass built with a class b fire resistant board that local yard sells that has 60 resistance, fitted with fire doors with intumescents so should keep them happy.
As to why Phil I won't pretend to know why, just doing as told, all I know is that the schools safety inspector or whatever he is, has said that if these wardrobes were built within the stage area that they need to have a minimum of 30min fire resistance.
I'd imagine that if the whole stage is on fire that the least of their worries would be the clothes and props in the wardrobe! but hey ho. Then again , it is containing what else can catch fire I guess.

 

Thanks Chippie, I thought it an odd request to be honest, I read the email myself that the inspector had sent the care taker and it did read that if it's on the stage it needs to be 30min resistant, there could have been a confusion in discussions prior to this though, unless it's more to do with it being a primary school I don't know, not the usual environment I work in.
Inspector talking bs could be the explanation though.