ᐅ Basement made of waterproof concrete or Poroton blocks?

Dear community,

I am reaching out because I am currently uncertain and, even after consulting specialists, I still do not have a clear answer.
We are building a house (KFW 40 standard, made of Poroton) on a slope, and our basement is partially underground. The plan was for the basement to be a "white tank" waterproofing system. However, we were recently informed that the basement will be built using Poroton T7 blocks (42.5cm (17 inches) thick), essentially a "black tank" system. Additionally, drainage will be installed.
Switching to a white tank would delay the start of construction.

My question is, would you insist on the white tank method? Generally, the black tank is considered to have a shorter lifespan, but for living comfort, the Poroton basement is supposed to be more pleasant.
I would also be interested to know if the basement made from Poroton T7 blocks might even be less expensive for the builder.
I hope you can help me.

Why should the waterproof concrete slab delay the start of construction? It also comes as a precast element from the concrete plant, produced within 1-2 weeks.

Honestly, I don’t think this is being communicated clearly, and yes – the waterproof concrete slab probably costs the general contractor more...

Robert1995 schrieb:

Now to my question, would you insist on having a waterproof concrete structure (“white tank”)?

It depends.
1. What compensation do you receive,
and more importantly,
2. What does the soil report say?

If the construction company simply doesn’t want to do the waterproof concrete structure, then that’s their problem. Personally, I would say “a contract is a contract.” There is a big difference between a “black tank” (bituminous waterproofing) and a “white tank” (waterproof concrete structure), even though both have their reasons.

Robert1995 schrieb:

The plan was to have a basement constructed as a waterproof concrete shell (“white tank”). We were recently informed that the basement will be built using Poroton T7 (42.5cm (17 inches) block), basically a masonry structure without a waterproof concrete shell (“black tank”). A drainage system will be installed additionally.
Constructing a white tank would delay the start of the build.

Ordering a plane instead of a ship just because it is available faster is complete nonsense. Every building site places specific demands on the basement, and these must be followed. Cutting corners here means accepting construction defects!

Robert1995 schrieb:

Now to my question: would you insist on the basement being executed as a waterproof concrete shell? [...] I would also like to know if the basement made of Poroton T7 blocks might even be cheaper for the developer.

Whether this is actually a developer (or a general contractor, a term often mistakenly used by many homeowners) is crucial for whether you have any leverage at all.

Unfortunately, you haven’t introduced your project to us yet—so we cannot give any reliable recommendations on the best construction method for your house. If you are buying from a developer, you have no say. If you are the client working with an architect, have the architect not only design but also manage the tendering process, so that bidders (including general contractors if needed) deliver exactly what is specified. If you are a client who contracts a general contractor without a tendering architect, you have already made one of the most significant mistakes.

Robert1995 schrieb:

We are building a house (KfW 40 standard with Poroton) on a sloped site, and half of our basement is below ground level.

At least one initial suspicion would be that the best solution is not either porous blocks OR waterproof concrete, but BOTH.

If I’m right, the core issue here might be that a general contractor contracted without a tendering architect has been told by their energy consultant that they cannot achieve the planned wall thicknesses with concrete, so now they want to switch to masonry?

---

https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/

Then show us what you consider to be half.

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

A waterproof concrete shell, in my opinion, is the more durable solution.

Yes, the waterproof concrete shell is also more expensive.

Did the contractor miss the deadline and fail to order the concrete basement on time, or was a masonry basement planned from the start?

Robert1995 schrieb:

On average, the waterproofing membrane (Schwarze Wanne) may not last as long, but for the living experience, a basement made from Poroton bricks is supposed to be more comfortable.

From my personal experience: living in a hillside house with a precast waterproof concrete basement (WU concrete) is excellent and clearly better than the alternative suggested to you—mainly because I can sleep more peacefully without worrying about potential moisture issues caused by groundwater pressure on the slope. Additionally, I like the polished precast concrete surfaces in the living areas.

Making waterproofing repairs later on in a basement built into a slope is usually complex. So, in my opinion, it’s a no-brainer when ordering waterproof (WU) concrete.