"Peter Taylor" wrote in message
...
Bob Mannix wrote

Even if there were no insulation there in the first place, the
requirements
for 30 minute fire protection between the old house and the new loft
conversion would require new mineral fibre insulation beneath the floor
of
the loft conversion, nailed to the joists. To remove it would be highly
irresponsible.

You are right about the ceiling needing to be 30 minute FR, but this is
achieved
by the plasterboard and skim (or by lath & plaster in older property).
Thermal
insulation material laid above the ceiling adds nothing to the ceiling's
fire
resistance. As I said, the original insulation to the area of the new
loft
floor should have been removed - this is not needed as there will be new
insulation on/between the rafters. The original insulation in the eaves
should
remain unless the new rafter insulation is carried on down the slope to
joist
level.


I don't believe you are correct. A single sheet of skimmed plasterboard is
insufficient to provide the fire protection (unless it is Fireline
plasterboard). The requirement for mineral fibre insulation was part of the
fire protection requirements for my loft conversion and its protection was
added to that provided by the ceiling to make up the required 30 minutes. A
depth of 65mm of mineral fibre insulation, nailed to the joists either side
was required (glass fibre is not allowed as it melts). The floor was not
allowed to be laid until the BCO had inspected the installation of the
mineral fibre.

Two sheets of plasterboard with a 12mm (AFAICR) gap would also do, but
that's a lot more difficult.


--
Bob Mannix
(anti-spam is as easy as 1-2-3 - not)