In article , nightjar
writes
"Tim Mitchell" wrote in message
...
We are building some more offices on a mezzanine floor above some existing
offices. The mezzanine floor is wooden joists with chipboard flooring.
Beneath the joists is a suspended ceiling with 600x600 tiles.
snip

The fire resistance of the panels is not the only factor. In a fire, a
strong updraught can develop, which would lift the tiles and allow the fire
past them. We did get a suspended ceiling approved some years ago, but the
grid had to be steel and we had to fit special clips to hold the tiles down.

Bearing in mind that the heat from the fire could (and would) cause the
steel grid to expand and buckle -- possibly to the point where the clips
could not hold anything down -- might it not be a wise precaution to
paint the joists and the underside of the floor above with a "fire
resistant", intumescent paint?

--
Paul