Building a single-family house in NRW

Soundproofing... interior walls made of aerated concrete are like no interior walls at all..

We have all faced this problem before.

In total, I spoke with about 20 providers, of which only three were prefabricated house providers.
In the end, I had the best experiences in conversations with construction companies that either have their own architect or cooperate with one and can still offer a fixed price.

To handle the problem of comparability and varying services, I created an Excel list and wrote down almost every term (e.g. grounding electrode, tiles for 30€/m², etc.) that appeared in a (construction and services) description of any provider.
I then asked each provider whether that term was included in their service.

In the Excel, I noted the surcharge for that feature for each provider and thus obtained the total costs for each provider.

If it’s not listed, it’s not included.

This is extremely tedious but in my opinion absolutely useful, especially if you as the builder have no idea and don’t want to get ripped off.

Regarding ventilation: it is primarily a luxury, yes.
But necessary if you are too lazy.

As the colleague said, airing out five times a day for 10 minutes each would be great.
Three times minimum.
If both of you work full time, you probably won’t even manage that.
If you don’t manage it, mold formation is very likely.
Especially in the first weeks/months when the building is still damp.
Why is that? With today’s standards you can assume that the house is quite tight. Moisture does not get out without ventilation.

Personally! I don’t know anyone who manages this regularly. That does not mean there isn’t someone, but I think most people won’t manage it properly.

To decide on a provider I would strongly recommend you to look at houses from these providers and also talk to the people about their experiences.
Look at construction sites, how they look and which craftsmen are used there.
Look at the construction company itself, what does their yard look like? Does everything make an impression of being proper or is it chaotic?

Furthermore, I recommend reading through this forum on such topics and equipment. For common topics (such as whether controlled residential ventilation is necessary or not) there are already countless and well-worn discussions.

Thank you for your contributions. Regarding the companies that are shortlisted, I believe they are construction supervisors?! They have their own architect they work with. The concept looks like this: payment to the companies after completion of each construction phase. (We are allowed to help choose the companies).

An invoice came up: Company from Sonsbeck (master mason)

110 sqm (which he probably misunderstood! We wanted 120 with additional expansion area in the attic)

KFW 55
Gray windows
Electric shutters
Concrete staircase
Solid wooden staircase upstairs
9m garage
Prepared roof truss
Branded sanitary fittings are included.
Underfloor heating as well
Deep drilling (without external unit)
Ventilation system
Small bay window in the living room.
Shower in the guest WC.
Also included all incidental costs, own contribution for the floor coverings and walls.

In summary: BKOG 370,000€??
Realistic?

Soundproofing... Interior walls made of aerated concrete are like having no interior walls..

I think that's a mantra of yours.

In the end: BKOG €370,000??
Realistic?

I googled yesterday for providers in Sonsbeck. One of them had this strange indication of a lower and upper construction cost limit in their offers (with a flower name, very nice). Whether this is supposed to be a range of a rough estimate calculation or whether he has two buddies for all trades and in the worst case always has to take the more expensive one because the cheaper one has no time, resulting in this upper limit? - I don't know.

Whether "realistic" or not, you can never say so easily based on square or cubic meters – for that you would have to have read the construction service descriptions.

Am I right to assume that you are also building in Sonsbeck and have to build KfW55 because of the local regulations for non-local interested parties?

No, we intend to build in Kamp-Lintfort. For us, it does not matter whether KFW 55 or not. However, you do get funding, and since we are going into it with little equity, we thought it would be an advantage.

No, we plan to build in Kamp-Lintfort. For us, it doesn't matter whether it's KFW 55 or not.

Kamp-Lintfort, I think Alfred’s grandmother came from there (just kidding).

However, you do get subsidies, and since we’re going into this with little equity, we thought it would be an advantage.

KfW55 seems achievable to me with reasonable means. The Energy Saving Ordinance 2016 will not be the last, so a few grams more are certainly acceptable. This little bit of “avant-garde” doesn’t hurt.

However, I warn against construction financing calculations that require KfW55 as a condition for the numbers to work out. If that is the case, the budget, seen without rose-colored glasses, is actually too tight.