ᐅ Materials for Sealing Joints Between Stairs and Walls, Soundproofing?

Hello, we recently moved into a house built in 2012, which has three fully enclosed concrete staircases connecting the floors. We have noticed that the house is extremely noisy, especially between the floors despite the concrete ceilings and enclosed staircases. This is because the staircases are not properly sealed to the walls; on the lower floor, you can even see light through the gaps at the sides into the floor above. My question is: what is the best way to seal these cavities? My father suggested using expanding foam, but does that effectively reduce noise? Once you spray foam into a gap, you can’t remove it... I would appreciate advice on which material should be used for sealing. Silicone probably won’t work, as the gaps are several centimeters (inches) wide in some places. Thank you very much for your assessment.

Nakleven schrieb:

The joints are several centimeters wide in some places (several inches).

Could it be that this was intentionally left open to provide the necessary decoupling of the staircase from the wall in order to prevent impact sound transmission?

Otus11 schrieb:

Could it be that this is intentionally left open to achieve the necessary decoupling of the staircase from the wall to prevent impact sound transmission?

That is likely the case.

If the stairwell is open anyway, sealing the joints doesn’t make much sense. Expanding foam is the wrong material. To put it simply, you insert a thick cord into the joints and then seal over it with a permanently elastic material, such as silicone, bituminous sealant, or similar…

The stairs are enclosed, but in terms of noise transmission from floor to floor, it sounds as if they are open. For example, when a baby cries in the attic, you can hear it clearly in the lower floor, as if standing right next to the child, despite concrete ceilings and sealed doors. We have clearly identified the stairs as the source of the problem. I am attaching a photo to show the joint I am referring to. As you can see, the joint is also uneven. Impact sound is not an issue; the stairs are extremely quiet to walk on.

Yes, insert a string line and then apply silicone properly.
I would doubt that the stairs are to blame, but trying it only costs a few euros.

And this gap is supposed to be bigger than the stairwell itself? Hard to believe.

Silicone, or if the gap is really large, maybe an expanding foam sealant tape. Not spray foam.