"Dave Liquorice" wrote in message
ll.com...
On Sun, 30 May 2004 07:14:21 +0000 (UTC), Philip Roberts wrote:

I've built a timber frame around it, which I'm going to cover with
two layers of 12.5mm plasterboard and have skimmed.

Don't forget access, not just for maintenance you mention a rodding
eye but you also have a hand between floors cable duct for phone,
network, TV etc. It almost certainly runs from roof space to ground
floor as well...

Question is - should I insert Rockwool in it's 'natural' state, ie,
unpack the stuff and let it expand to its maximum,
snip
should I cram as much Rockwool into the void as I possible can?

TBH two layers of 12.5mm plasterboard are going to do far more than a
bit of rockwool no matter how much or little you put in. Make sure
that there are no holes/cracks for the sopund to sneak through as
well. Stagger and board joints buy as much as possible indeed I'd be
tempted to seal the edges of the lower layer of board before putting
the top layer on and seall all those edges as well.

Thanks for this; all sounds very sensible and have done all the above today.
After reading this and the other replies I decided that my access panel was
likely to negate much of the good work, so after much thought I've made this
only "semi" removable, in that it has three layers - MDF innermost, which
nestles snugly within the timber studding; then a larger square plate of
plasterboard (about 0.5" larger all round); then a second plasterboard
plate, 0.5" larger all round than the first. I carefully cut the two plates
out from the plasterboard I used for the actual boxing in, so they are a
precise fit. When the panel is inserted into the matching hole, it's flush
on the outside, and there is therefore a double-stepped interface to prevent
sound leakage. The plan now is for the plasterer to skim over the whole
lot, and he'll just score a line along where the gap is, to define the edge
of the panel (held in by dome-capped mirror screws). In the unlikely event
of my ever needing to access the rodding eye (I've never needed to do so
before in my life!) I'll have to break the plaster seal, but meanwhile, the
soundproofing should be pretty good.

Worth looking at I would have thought or maybe some heavy matting to
sandwich between the PB layers.

Sounds a good one but the BCO specified two back-to-back layers of PB to
give the requisite amount of fire protection (BCO isn't concerned about the
noisy turd issue!)

David