This is a sort of DIY question since my business is moving to new
offices and we are doing some modifications ourselves.

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.

The BCO wants 30 minute fire protection for this mezzanine floor. This I
agree with. Our suspended ceiling contractor says that the existing
ceiling tiles provide 30 minutes fire protection, provided that any
recessed light fittings are properly hooded. He has given me the
manufacturer's specs for the ceiling tiles showing this. The BCO says
that it does not provide the protection and we need to plasterboard the
underside of the joists to provide the fire protection.

I don't want to antagonise the BCO by arguing that he's wrong, but I
don't want to do a lot of extra work if it's already suitable. Advice
from the panel please.
--
Tim Mitchell

"Tim Mitchell" wrote in message
...
This is a sort of DIY question since my business is moving to new offices
and we are doing some modifications ourselves.

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.

The BCO wants 30 minute fire protection for this mezzanine floor. This I
agree with. Our suspended ceiling contractor says that the existing
ceiling tiles provide 30 minutes fire protection, provided that any
recessed light fittings are properly hooded. He has given me the
manufacturer's specs for the ceiling tiles showing this. The BCO says that
it does not provide the protection and we need to plasterboard the
underside of the joists to provide the fire protection.

I don't want to antagonise the BCO by arguing that he's wrong, but I don't
want to do a lot of extra work if it's already suitable. Advice from the
panel please.

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.

Colin Bignell

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

In article , Paul C. Dickie
writes
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?

Well I am only going on what the ceiling manufacturers say. They say
that the ceiling itself, without the tiles being clipped, will give 30
mins fire protection to the floor above.

The alternative is to put a layer of plasterboard above the ceiling
tiles but if the ceiling itself is OK, this should not be necessary. The
offices above have a fire exit direct to outside and can be evacuated in
about 2 minutes, so 30 minutes should be ample.
--
Tim Mitchell

"Tim Mitchell" wrote in message
...
In article , Paul C. Dickie
writes
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?

Well I am only going on what the ceiling manufacturers say. They say that
the ceiling itself, without the tiles being clipped, will give 30 mins
fire protection to the floor above.

The alternative is to put a layer of plasterboard above the ceiling tiles
but if the ceiling itself is OK, this should not be necessary. The offices
above have a fire exit direct to outside and can be evacuated in about 2
minutes, so 30 minutes should be ample.

The requirement for fire resistance is not based on how long it takes to
evacuate the compartment under ideal conditions. It is intended to provide
adequate protection for someone trapped inside while the Fire Brigade arrive
and make a search. There have been numerous cases where a fire exit has
proved to be useless for one reason or another and a surprisingly large
number of people either panic or freeze when faced with a real fire. Our
mezzanine was deemed to require two hours' fire resistance.

Colin Bignell

On Thu, 14 Oct 2004 01:24:33 +0100, a particular chimpanzee named
"nightjar" randomly hit the
keyboard and produced:

The requirement for fire resistance is not based on how long it takes to
evacuate the compartment under ideal conditions. It is intended to provide
adequate protection for someone trapped inside while the Fire Brigade arrive
and make a search.

The 'period' of fire resistance is more like a relative measure of the
level of protection. A structure or door, etc, which achieves 30
minutes FR in a standard test may last for hours in a real fire, or
may collapse or fail in a shorter time. An extreme example: the WTC
Twin Towers had a period of two hours, but the South tower collapsed
in 56 minutes. The conditions experienced were a lot more severe than
those in a standard test.
--
Hugo Nebula
'What you have to ask yourself is, "if no-one on the internet wants
a piece of this, just how far from the pack have you strayed?"'

Hugo Nebula abuse@localhost wrote:
On Thu, 14 Oct 2004 01:24:33 +0100, a particular chimpanzee named
"nightjar" randomly hit the
keyboard and produced:

The requirement for fire resistance is not based on how long it takes to
evacuate the compartment under ideal conditions. It is intended to provide
adequate protection for someone trapped inside while the Fire Brigade arrive
and make a search.

The 'period' of fire resistance is more like a relative measure of the
level of protection. A structure or door, etc, which achieves 30
minutes FR in a standard test may last for hours in a real fire, or
may collapse or fail in a shorter time. An extreme example: the WTC
Twin Towers had a period of two hours, but the South tower collapsed
in 56 minutes. The conditions experienced were a lot more severe than
those in a standard test.

And the protection may not have been as specified.