Given this information, is it reasonable to assume that the ceiling should be constructed using fire-rated boards to ensure adequate fire protection ?

From my renovation I recall that you don't necessarily have to use special fire boards - ordinary 12.5mm boards plus a skim were adequate for some requirements (I don't recall off the top of my head whether it was 30, 60 or 90 mins) - but certainly kept my BC happy in our 3-storey home.

   - Andy.

'pink board' as our local merchant calls it has among other things glass fibres in it, and because of this is rather better at holding together once the paper facing has burnt off than the cheaper pure gyproc. Sometimes at holes etc it looks a bit 'hairy' and this allows it to be identified.

In some constructions this reinforcement may not be needed to achieve a 30 mins resistance as the board is mechanically well supported  some other way. I'd be very careful of anyone claiming that ordinary board was generally going to meet 30mins, and determining the rating of any non-standard arrangement is a specialist job and rather more than a desk study and comparing labels . - hence why the folk who make the fire rated fittings etc do so many tests, and BCOs and the like go on courses to learn this stuff.

Mike

As I recall the 12.5mm plus skim was a standard/well recognised arrangement (I'm sure there was something in the AD or some compliance guide at the time but I can't locate it now). As you say, strength is lost when the paper surface is burned away - presumably the plaster skim was thought to prevent that. As I recall that was only one of several "usual" options - two layers of plaster board with all joints staggered was another if I remember correctly.  Wet plastering seems to be going out of fashion though, with many builders preferring tapered edge and simple jointing - so fire rated board can simplify things a lot.

   - Andy.

You are correct AJ. We used to use, and continue to refer to, BRE's "Guidelines for the Construction of Fire Resisting Structural Elements" published 1988.

Table 14(B) of that document allowed one 12.5mm layer of standard plasterboard + 5mm of gypsum board finish plaster. The assessment assumed joists of 37mm breadth with depth and span suitable to support imposed load, floor at least 15mm softwood tongued and grooved. Plasterboard supported 40mm galvanized nails at 150mm centres.

You are correct AJ. We used to use, and continue to refer to, BRE's "Guidelines for the Construction of Fire Resisting Structural Elements" published 1988.

Table 14(B) of that document allowed one 12.5mm layer of standard plasterboard + 5mm of gypsum board finish plaster. The assessment assumed joists of 37mm breadth with depth and span suitable to support imposed load, floor at least 15mm softwood tongued and grooved. Plasterboard supported 40mm galvanized nails at 150mm centres.