Basement made of WU concrete or Poroton?

Dear Community,

I am reaching out to you because I am currently uncertain and even after consulting with experts, I still have no clear answer.
We are building a house (KFW 40 made of Poroton) on a slope and our residential basement is half submerged in the ground. The plan was for a basement as a [Weiße Wanne]. We were recently informed at short notice that the basement will be built from Poroton T7 (42.5 cm stone), basically a [Schwarze Wanne]. Additionally, a drainage system will be installed.
A [Weiße Wanne] would delay the start of construction.

Now to my question, would you insist on executing it as a [Weiße Wanne]? On average, the [Schwarze Wanne] is said to be less durable, but for the living comfort, the basement made of Poroton is supposed to be more pleasant.
I would also be interested to know if the basement made of Poroton T7 stone is even cheaper for the developer.
I hope you can help me.

Why should the white tank delay the start of construction? It also only comes as a prefabricated part from the concrete factory, produced within 1-2 weeks.

I honestly don’t think that is being communicated properly and yes - the white tank probably costs the general contractor more...

Now to my question, would you insist on the execution as a white tank?

It depends. 1. What compensation do you get credited and what is much more important 2. What does the soil report say If the construction company simply doesn't feel like doing the white tank, then they're out of luck. Personally, I would say "a contract is a contract." Black tank and white tank are a big difference (even if both have their justification).

A basement as a white tank was planned. Short-term, we were now informed that the basement will be built from Poroton T7 (42.5 cm block), basically a black tank. Additionally, a drainage system will be installed.
A white tank would delay the start of construction.

Ordering a plane instead of a ship because the plane is available faster: that is sheer nonsense of the highest order. Every building ground places its demands on the basement, and those must be followed. Letting things slide here means accepting construction defects!

Now to my question, would you insist on the execution as a white tank? [...] I would also be interested to know if the basement made from the Poroton T7 block might even be cheaper for the developer.

Whether it is even a developer (or rather a general contractor, often mislabelled as such by many builders) significantly determines whether you have a say at all.

Unfortunately, you have not yet presented your project to us—therefore, we cannot give any serious recommendation on how to build this house best. If you are a buyer with a developer, you have no say. If you are a builder with an architect, then have the architect not only plan but also tender, and have the bidders (even as a general contractor, if you like) deliver what is required. If you are a builder with a general contractor contracted without tendering by an architect, you have already made one of the most significant mistakes.

We are building a house (KFW 40 from Poroton) on a hillside, and our living basement is half embedded in the earth.

At least I see a suspicion here that the most suitable variant would neither be porous blocks NOR (WU-) concrete, but BOTH.

If I guess correctly, the crux of the problem is this: general contractor contracted without a tendering architect, whose energy consultant has now said that with concrete he cannot achieve the planned wall thicknesses, and now he prefers to do masonry?

Then show us what you understand by half.

I would first want to see how the house on the slope is planned.

[Weisse Wanne] is, in my opinion, the more durable solution.

Yes, the [WW] is also more expensive.

Did the contractor sleep on it and not order the concrete cellar in time or did he plan the masonry cellar right away?

On average, the black tank is not supposed to last as long, but for the living comfort, the basement made of Poroton is supposedly more pleasant.

I can say from my own experience: living in a hillside house with a prefabricated WU concrete basement is excellent and significantly better than the alternative that was suggested to you: already because I can sleep more peacefully regarding possible moisture problems due to pressing water on the slope. Additionally, I like the polished prefabricated surfaces in the living area.

Later waterproofing repairs in a hillside floor are usually complex. So from my point of view, it’s a no-brainer when WU concrete is specified.