John Sayers' Recording Studio Design Forum Archive

Hi there Stuart,

As we are ready to start our construction of a booth in a basement, I would ask for your help with the following options:

1. Existing Brick Wall, Rock Wool 50kg/m3, Air Gap, Rock Wool, Double Dry Wall?

2. Existing Brick Wall with 2 Plaster Boards screwed directly to wall with no gap, Rock Wool 50kg/m3, Air Gap, Rock Wool, Double Dry Wall?

Which of these would you suggest and what would be gain in insolation in DB`s from the second suggestion?

As I want to commence construction asap, your knowledge and kind help would be gratefully appreciated.

Regards.


Andrew.

...with the following options:

1. Existing Brick Wall, Rock Wool 50kg/m3, Air Gap, Rock Wool, Double Dry Wall?

2. Existing Brick Wall with 2 Plaster Boards screwed directly to wall with no gap, Rock Wool 50kg/m3, Air Gap, Rock Wool, Double Dry Wall?

Which of these would you suggest

The key is this: How much mass does the two extra layers of drywall add to the brick wall?

The density of brick is roughly 2300 kg/m3, so assuming a typical 20cm thick brick wall, the surface mass (surface density) would be about 460 kg/m2. The density of drywall is roughly 680 kg/m3, so two layers of 16mm drywall would have a surface mass (surface density) of about 22 kg/m2. So your 2 layers of drywall on the brick would increase the mass of the wall by a bit less than 5%.

and what would be gain in insolation in DB`s from the second suggestion?

You don't say how thick the mineral wool is, or how big the air gap is in each case, so I'm assuming it would be the same: I'm assuming 10cm mineral wool, plus 5cm of air, plus another 10cm of mineral wool, for a total air gap of 25cm.

Your isolation in the first case (brick without extra drywall) would be roughly 61.5 dB. Your isolation for the second case, with the extra two layers of drywall up against the brick but everything else the same, would be about 61.6 dB.

Yup. That's correct. You would get an increase n isolation that you would not even be able to measure, and would certainly not be able to hear!

Essentially, there is no difference. The extra mass of the drywall is negligible, compared to the mass of the bricks.

You would get a better improvement in isolation by rendering (plastering) that wall, then painting the plaster with a good masonry sealer.

You would also get a better improvement in isolation by completely filling the air gap with insulation, rather than leave empty air in the middle.

- Stuart -