owed soundproofing terraced house new build

Good morning,

as I read in my other thread ( ), I have some problems with the planners of our terraced house. The positive thing currently is that the executing trades, i.e. the contracted construction company, are doing a good job. However, we have now encountered a serious problem concerning sound insulation. The situation is as follows:

We are buying a terraced house from the developer. The developer here is practically a special-purpose GmbH and not one of the big developers. The terraced house was built with a single-layer wall (30cm calcium silicate brick with high bulk density). We then demanded a sound insulation certificate. It was then found that the required sound insulation level is not met, and a 9.5cm facing shell is to be installed in order to achieve a value of 62dB. I have read several times that the recognized standard of technology is a double-shell construction and that in such a terraced house typically an increased sound insulation of 67dB is owed. A clarification appointment is expected to take place next week, for which I would like to prepare a bit and therefore ask for your assessment.

The contract with the developer states the following:
"The minimum requirements according to DIN 4109:2018 for building acoustics (sound insulation in interior rooms) are met."

Furthermore, it states:
"The seller undertakes to deliver the contractual object according to the construction description including building plans and the recognized rules of building engineering, turnkey and functional for the agreed residential use."

According to my research, however, the minimum requirements do not correspond to the recognized rules of technology, which raises the question of whether 62dB or 67dB sound insulation is required. Could you help me here?

if a facing shell is installed on both sides of the partition wall, what is then achieved?

How are cables routed vertically, if it's a terraced house then there are 2 neighbors and both partition walls should be free of cables

If a facing shell is installed on both sides of the partition wall, what is then achieved?

The facing shell is only installed on our side (right side in the picture), as on the left side (middle terraced house) the stairwell adjoins and the stairs are already installed. In the picture you can see the partition wall; the other partition walls only concern the building services room on our side as well as the bathroom on the upper floor (which already has facing installations) and a children's room where a facing shell is also to be installed.

The objective is to achieve sound insulation of over 62 dB with sufficient certainty. However, I am not sure whether rather 67 dB would be required. This is not achieved hereby. Moreover, it is of course very annoying because we lose about 10 cm in the children's room and the living/dining room, and the kitchen also has to be somewhat redesigned.

How are the cables routed vertically,

There are no cables on either side.

Good day,
I would be concerned not only about the soundproofing but also about the purchase or construction contract.
A terraced house is always separated from the next terraced house by a two-shell partition wall. Otherwise, it is called a multi-family house.
If you buy or have a terraced house built, it must later be possible to dismantle it independently of the neighbors. The same applies to a semi-detached house.
However, if the houses are only separated by a single-shell partition wall, this is likely not possible.

Please check this and make sure to have the soundproofing reviewed by an independent soundproofing expert.
In my opinion, a facing shell will not achieve the value of 62 either.

Regards

A terraced house is always separated from the next terraced house by a double-leaf partition wall. Otherwise, it is referred to as a multi-family house.
If you buy or build a terraced house, it must later be possible to dismantle it independently of the neighbors. The same applies to a semi-detached house.
However, if the houses are only separated by a single-leaf partition wall, this is probably not possible.

Do you have a source for this? To my knowledge, this is not the case, but it is indeed possible to build terraced houses that share a wall. In most cases, this is probably no longer done, precisely because of sound insulation issues. But it is possible and, to my knowledge, does not lead to the terraced houses becoming a multi-family house.