On Sun, 30 Dec 2007 15:12:50 -0800 (PST), a particular chimpanzee,
Richard randomly hit the keyboard and
produced:

Hi, I'm about to embark on boarding out my loft for light storage, and
felt that it would be a good time to also remedy the lack of fire
breaks in my mid terrace house. I cant seem to find any advice about
firebreak specifications or building regs so would be grateful if I
could be shown in the correct direction. I cannot decide whether to
build up the tops of the dividing walls (visible) with block and
mortar (if so is there a specific specification? I was thinking
fixing firfix to the dividing chimneys for e.g.) or with stud and
plasterboard (again what is the spec). I feel the latter would be
easier but the former may be more sturdy/soundproof. Any advice on
which to choose and how to go about it would be gratefully received.
How do you fix to the roof if the rafters dont line with the wall -
can you use noggins in wood? Many Thanks, Richard.

Are you doing this in conjunction with your neighbours? If not it's
at least best to warn them what you're doing. Strange knocking noises
directly above their bedroom ceilings may get you complaints via
Environmental Health and Building Control. It's also going to be a
lot easier and more effective if you can get to both sides of your new
party wall.

So long as you're not making the situation any worse in terms of
structure or fire safety than before, the work is not subject to
Building Regulations. The Party Wall Act may have a bearing on what
you're doing, but this is a civil matter between you and your
neighbour(s).

Masonry is obviously easier to do from one side, is more robust, and
will resist sound transmission better. Lay your blocks flat rather
than trying to lay two leaves, make sure that they are well mortared
to avoid air paths, and fill the space between the wall and the
felt/covering in Rockwool.

If you want a party wall in studwork that will form an effective sound
barrier, it needs to be done as two separate stud walls, each
independent of the other, lined with 2 layers of 12mm plasterboard on
each side. A single stud could be used, but it wouldn't form any
serious impediment to noise. It would also not help you very much if
there was a fire in your neighbours unless you could plasterboard
their side of the stud wall (if they have a fire, the timber on their
side is unprotected and would burn through, collapsing the stud wall).
As you say, you can noggin between the rafters, but fill the space
over the top with Rockwool.

If it's just life safety you're worried about, a third option could be
a 'cavity barrier' such as Rockwool Fire Blanket
(http://www.rockwool.co.uk/sw55784.asp).
--
Hugo Nebula
"If no-one on the internet wants a piece of this,
just how far from the pack have you strayed?"