Double plasterboard works well, you still need rockwool but solid partitions are best.

Hi Nigel,

We are trying to achieve 40 decibels or less. As a supplemental, we also need to consider the acoustics between floors. Anyone got any recommendations for this?
Tony, someone suggested using acoustic board rather than double plasterboard, as it was more cost effective....don't know what your thoughts are on this????

Decisions, decisions decisions!!!!

some useful info there Timber, was worth reading :)

Not better, but as good, perhaps i could have made that a little clearer. Masonary is good but no better generally than lightweight.

The actual performance of the walls (in terms of performance at certain frequencies) is different, but the overall performance (in terms of single figure value) is pritty similar for a set thickness.

Mass law is one of the fundametals of acoustics, but with layers and air gaps, simlar performances can be achieved.

Lets take a standard timber party wall consisting of two timber frames separated by a 50 mm cavity, with mineral wool inside and one layer of 19 mm plank and one layer of 15 mm wallboard to either room face VS a solid wall consisting of 215 blocks (laid flat) plastered on either room face, the performance will be similar. With the solid wall, it is let down because there is a physical connection between both sides.

Modern masonary walls consist of lightweight blockwork and a cavity, but the blocks are light, and don't tend to work quite so well at higher frequencies.

Timber walls work well at high frequencies, but are let down a little at the lower end of the spectrum (a bit 'boomy').

A good timber wall as above can exceed building regs, by 10 dB (55 dB DnT,w + Ctr vs min of 45 dB)

A good masonary wall can hit the same value.

Flanking sound (sound skipping round the element in question (regardless of construction type)) can play a big part too.

Timber

Nice explanation Timber - thanks.

From what you've said though, I would imagine that cavity construction of twin heavyweight blockwork, rendered both sides would have the benefits of both mass and [near] structural seperation, outperforming the examples given above?

Filling the cavity with fluffy stuff making it even better?

Mike, yes, a heavy weight masonary cavity system can out perform the construction types mentioned above but a lot of this depends on the other elements performing well (like external walls, doors and windows).

You can reach a certain level with walls and floors where the performance of the separating structure ends up limited by other elements.

As a general rule of thumb though is that either you wants lots of mass or lots of separation, or a bit of both.

Timber

Mike - indeed.

The above floor spec will be 'ok' for impact (carpets make a big difference).

If its a masonary floor, a thin resilient layer works really really well because there is enough mass to absorb the foot fall energy, plus masonary floors won't deflect as much on impact.

With timber there is less mass to absorb the foot fall energy and more deflection from the structure, but to get good performance it is always better to stop the impact at source, so it is better to install a floating floor of some sort. Propriatory flooring boards can be bought, but a laminate of dense mineral wool and chipboard works wonders.

Timber

Do you mean cement bonded particle boards?

Yeah thats the same stuff.

Its pritty good in terms of mass, but isn't quite as 'dead' as plasterboard so resonance can be an issue.

Timber

A thin resilient layer (5+ mm) will make a resonable difference when stuck on top of a concrete floor. You should quite easily be able to notice a differnce.

Essentially it doesn't have to be an 'acoustic' underlay, all they are is rubber or dense foam or both! If you can find something similar off the self at a flooring shop then it should do just as well.

Timber