Question about soundproofing with drywall

We will build a one-and-a-half-story house with a knee wall height of 1.30 meters in solid construction. There is some railway noise in the building area, but we do not find it excessively disturbing, especially since the existing open space in between is partly going to be developed.

However, we were advised externally to consider double drywalling the slopes in the upper floor for sound insulation purposes. The attic already has a thicker roof structure with 200 mm mineral wool insulation due to KfW70 standards.

Now we have the dilemma: single or double drywalling (12.5 mm) in the upper floor. Since we have already installed a very high knee wall and more insulation in the roof, the question arises for us whether the extra investment in double drywalling is really worthwhile.

Does double drywalling absorb that much more sound? Are 1000 euros in additional costs well spent?

Hello,

I can't tell you how much sound a double lining absorbs.

But what about your ventilation habits? Do you need a lot of fresh air (open windows) at night?

Have you planned a controlled ventilation and exhaust system?

The nicest double lining is of no use to you if the windows are open...

Regards,

Dirk

We are installing a central ventilation and exhaust system.
The windows will therefore usually remain closed.
Windows of the SSK 3 will also be installed.

Double-layered drywall should actually be standard anyway, not just for soundproofing reasons.

No idea... I have no experience with that. Hopefully, a few "specialists" will chime in here.

Hello,

Since we have already installed a very high threshold and additional insulation in the roof, the question arises for us whether the extra investment in double drywalling really makes sense. Does double drywalling absorb that much more sound? Is an additional cost of 1000 euros well spent?

I would not want to call it "more" insulation now; we already work with 240 mm as standard.

Double drywalling does make sense in your case; for example, in our Cologne area, it has even been included in the development plan by the city in some building areas due to high air traffic. The sound insulation value thus shifts from 38 Rw,RdB with a wall thickness of 125 mm to 55 Rw,RdB or even 57 Rw,RdB; depending on the insulation thickness. In case of busy rail traffic, I would recommend following the advice of your site manager.



Double drywalling is not part of the usual standard, as it is not required everywhere.

Best regards from the Rhineland