Internal sound insulation for single-family house/semi-detached house - Questions

Hello everyone,

I have a question about soundproofing and hope that you might be able to help a little. First of all, a big thank you in advance!

Through our developer, we built an "almost" turnkey HDHH, with only the floor coverings and tiling as owner-provided work. The architect and structural engineering were provided by the developer.

The interior and exterior walls are made of aerated concrete. The exterior walls (without plaster) are 36.5 cm thick, but the interior walls on the upper floor are only 11.5 cm thick plus exterior plaster. On the upper floor, this results in about 13-14 cm including the plaster. On the upper floor, there are 2 children's bedrooms, the parents' bedroom, and the bathroom. The upper floor is extremely noisy / lacks sound insulation; if one child wakes up at night and cries, the other child usually wakes up too, and it becomes extremely stressful. We only use the toilet and shower in the morning or when the children are still awake. Our construction contract does not address soundproofing; it only states that the same bricks are used inside the house as those used for the exterior wall.

Fortunately, we do not hear our neighbors at all.

Of course, we checked and signed off the architect’s plans before construction began, but we were not advised at all about soundproofing and thus did not consider it. We have now withheld the final payment of about €2,000 and pointed out to the developer what we understand to be a deficiency. The developer replied that for single-family/semi-detached houses, i.e., non-multi-family houses, no soundproofing measures are required and immediately demanded the withheld amount of around €2,000 from us. "The soundproofing proof has been provided," it says in his last letter?!

I also "googled" the whole topic and found many pages on it, but the matters mostly referred to multi-family houses, for which there is a VDI Guideline 4100 that should be used as a basis for the general rules of technology...?! Does this guideline not apply to single-family houses, i.e., to a house with only one dwelling unit?

We feel pretty cheated because we paid a lot of money and now have to live with such thin and sound-permeable walls. Retrofitting adequate soundproofing measures would certainly cost more than the amount we withheld.

As a next step, I would like to commission an independent expert but do not know if it is even worth it since I can find nothing in the contract with the developer regarding soundproofing. Does anyone know a good expert in the Mannheim/Darmstadt area?

One last thing:
In our development area, this developer built about 17 houses; when talking to other homeowners, you find out that they have thicker walls on the upper floor everywhere and no one complains about too much noise on the upper floor.

Thank you very much for your hopefully numerous input and feedback regarding my problem.

Best regards Eliot

Hi,

if you haven't agreed on anything regarding soundproofing in the contract, the general rules of technology must be observed. And these are probably met by the installation of 11.5 cm thick aerated concrete walls (of course, there could be structural construction errors).

Unfortunately, your planner, if you had one, forgot to advise you before. Aerated concrete and good soundproofing are like black and white or fire and water. I assume you now have to deal with it as it is.

Regards

Hello Eliot,

The interior and exterior walls are made of aerated concrete. The exterior walls (without plaster) are 36.5 cm thick, but the interior walls on the upper floor are only 11.5 cm thick plus exterior plaster. On the upper floor, this results in about 13-14 cm including plaster ... Our building contract does not address the issue of sound insulation; it only states that the same stones used for the exterior walls are used inside the house.

Your seller made the first "mistake," your architect the second – both should have offered you lightweight walls or calcium silicate bricks (calcium silicate) as an alternative; despite their bad reputation, they offer better sound insulation than any 11.5 cm thick aerated concrete wall. The problem with 11.5 cm aerated concrete walls in the attic or upper floor is not a defect in the classical sense; your builder has complied with building regulations – E.Curb is completely right.

Fortunately, we cannot hear our neighbors at all.

That is hardly possible, since the party wall is probably made of calcium silicate plus an air gap ...

... however, we were not advised on the issue of sound at all and therefore did not consider it at all. We have now withheld the final payment of about €2000 and have pointed out the – in our understanding – defect to the builder. Our builder ... has immediately reminded us of the withheld amount of approximately €2000. "The soundproofing verification has been provided," it says in his last letter.

You should promptly pay the outstanding amount, because your builder has performed his contractual obligation; a soundproofing report should also be available.

You can – and this is really a very slim chance – try to prove misadvice by your builder. However, this requires independent witnesses who were present at every relevant consultation/planning meeting. If you cannot do this, you can save yourself the cost of an expert, because he will not tell you anything different.

You will have to live with this – for you – "defect."

Kind regards