How to make sound insulation of the attic?

Question

How to make sound insulation of the attic?

There is a private house 2 floors of aerated concrete with a cold attic.

— Attic floor: joists 50 x 150 mm with a spacing of 60 cm, inside the joists hermetically placed foam 10cm.

— roof – soft roof on the boards + 5 cm of rock wool inserted between the rafters of the roof.

— everywhere on the 2nd floor installed stretch ceilings and light fixtures. From the loft floor joists to the suspended ceiling – about 7-8 cm.

Naturally, the lack of a sound reflective layer is unacceptable: you can hear everything from one room through the attic from another room, etc. But the most annoying is the outside noise – the barking of dogs. But here most of the noise seems to come through the windows.

On the basis of all this I plan to do for the beginning 2 overlapping steps:

a. improving the sound insulation of the attic floor

b. improve the thermal insulation of the attic floor

Thermal insulation – I plan to screw transverse boards on the beams attic floor above and put on top of 2 layers of absorbent cotton 5 cm (insulation). Styrofoam will remain as well.

Soundproofing. It is clear that you need to add a sheet of material. Also note that lowering the ceiling below the current level is unacceptable (already too low).

The easiest option – remove the suspended ceilings, screw to the bottom of the joists 2 layers of gypsum plasterboard, lay fiberglass fleece, cover with silicone joints, etc. Then return the stretch ceilings in place. The next option – a one-level ceiling on the vibratory hangers (GFB + GPB + rockwool ultra-thin layer of wool) – i.e. 6 – 7 cm from the floor joists.

Please comment:

1. How critical for sound insulation that the foam will be left between the joists?

2. Given that the main problem – barking dogs – is limited in the solution due to the weak link, which are the windows.

And for windows, achieving insulation greater than 30 to 35 dB (and thus the entire wall) is problematic. Does it make sense to prefer a simple option (just lining 2 sheets of plasterboard)? Or still choose a more complex and expensive option with vibration hangers?

Yeller Brick

Answer

– Yeller Brick · Answer 1 · 2022-05-19 09:24:22

In your case you don't need any vibratory hangers.

Gypsum fiber + gypsum plasterboard + rock wool. The foam is better under the roof, and the wool between the beams.

Berlin

I realized that a satisfactory result will be if the lag inside is in two layers of gypsum fiber + gypsum plasterboard (and the final to leave a suspended ceiling). The joints are sealed with non-hardening sealant. Do I need to glue the joists and the perimeter of the walls with vibrostack in this case? Will it make any difference? Or there is no point and it will be enough just to fix them with self-tapping screws?

Regarding the foam plastic. Will it make the result worse if it is left? Or is it just a matter of a couple of decibels? If you want to clad, for example, not with gypsum fiber + gypsum board, but with OSB 11mm + gypsum board. Or gypsum board + gypsum board. Will there be similar options?

You don't have anyone going upstairs, it's a technical attic. Then why all these gadgets? You just need to weigh it down, create an airtight sound barrier and that's it. You can do OSB, you can do fiber-reinforced plaster. If you can do three layers, do it. In this case, the more the better :) Replacing the foam on the wool will have a tangible effect.

About the windows. Listen, look carefully, look at the window sills and the space under the window sill. Most often, it is not the window that is the weak link, but its installation and the bare foam, instead of quality plastered soffits.