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.
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.
G
Gerddieter28 Jan 2024 13:08hanghaus2023 schrieb:
The basement plan does not show any half-height walls.I agree, it’s all concrete, right?H
hanghaus202328 Jan 2024 13:16Gerddieter schrieb:
I agree, is everything concrete or not?Yes. It is designed as reinforced concrete.
However, in the section view, the wall is already masonry.
Is the section view part of the contract?
Robert1995 schrieb:
The shell construction company was selected by the developer after a tender, and presumably the cheapest option was chosen, that’s the assumption.
This company either cannot provide a waterproof shell ("white tank") or considers it not feasible within the schedule. However, I strongly suspect that the order was placed too late. Robert1995 schrieb:
This is a general contractor. So you have a contractual partner here who is probably more of an architect than a mason and does not carry out the shell construction as their own service; they have subcontracted the shell construction. The relevant subcontractor is not offering the expected price for the planned waterproof concrete basement (which they would presumably have to fully subcontract themselves) but instead proposes to build the basement walls themselves. From a technical perspective, I would only agree to this for the exterior wall on the valley side at best. As to what you can insist on from a legal perspective, we cannot determine that here: in the worst case, you have commissioned "a part of the house that looks the way it was drawn"...
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
P.S.: I find it concerning (and it raises red flags) when drawings mention open change orders. It would be important to clarify how the timing of the drawings relates to the contract signing. Is it possible that you agreed on a price before the quality of the deliverable was firmly established?
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
11ant schrieb:... so even worse: "take my money, and if you’re willing, then build me a house with it"???
What you can legally insist on is unclear to us: in the worst case, you have ordered "a piece of house, looking like the drawings" ...
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
A
Allthewayup28 Jan 2024 18:28The term "WU basement" is often used by homeowners (usually non-professionals) as a synonym.
Here, a distinction is made between the prefabricated system (concrete precast elements) which are cast on site with WU concrete (waterproof concrete), and the monolithic construction method where formwork is created on site and then also poured with WU concrete.
When discussing with my general contractor, "WU basement" was frequently mentioned, but it later turned out that only the prefabricated system following WU guidelines was used. Besides the many potential construction errors, this has another major disadvantage: any later injection sealing of leaks in the element walls is impossible because it can cause the bond between the element wall and the cast-in-place concrete to loosen over a large area, opening up additional water pathways. This is not a problem with monolithic construction.
So, my advice: do not opt for a WU basement using the prefabricated element method according to WU guidelines; instead, insist on a WU basement built with formwork according to DIN standards. If this is not contractually specified, it again leaves room for the construction company (financially and regarding long-term risk) at the expense of the homeowner.
I have read several scientific articles about the construction method with element walls and even saw a test where three core samples were taken, all of which showed that the bond between the cast-in-place concrete and the element wall was poor or insufficient. This is alarming if you rely on the waterproofing properties of such a construction method.
So far, our basement has remained dry (again), but I do not expect this to last for 40 years. Had I known this back then, I would have insisted on the formwork method and, if necessary, hired external basement specialists through separate tendering.
Unfortunately, savings are too often made at the foundation of the house, as is often witnessed. I consider a "black bathtub" (fully waterproof basement shell) on a slope a worst-case nightmare scenario—do not allow that under any circumstances. Weather patterns tend to become more extreme. You are definitely making a sensible investment in the basement if it is constructed to withstand groundwater pressure.
Here, a distinction is made between the prefabricated system (concrete precast elements) which are cast on site with WU concrete (waterproof concrete), and the monolithic construction method where formwork is created on site and then also poured with WU concrete.
When discussing with my general contractor, "WU basement" was frequently mentioned, but it later turned out that only the prefabricated system following WU guidelines was used. Besides the many potential construction errors, this has another major disadvantage: any later injection sealing of leaks in the element walls is impossible because it can cause the bond between the element wall and the cast-in-place concrete to loosen over a large area, opening up additional water pathways. This is not a problem with monolithic construction.
So, my advice: do not opt for a WU basement using the prefabricated element method according to WU guidelines; instead, insist on a WU basement built with formwork according to DIN standards. If this is not contractually specified, it again leaves room for the construction company (financially and regarding long-term risk) at the expense of the homeowner.
I have read several scientific articles about the construction method with element walls and even saw a test where three core samples were taken, all of which showed that the bond between the cast-in-place concrete and the element wall was poor or insufficient. This is alarming if you rely on the waterproofing properties of such a construction method.
So far, our basement has remained dry (again), but I do not expect this to last for 40 years. Had I known this back then, I would have insisted on the formwork method and, if necessary, hired external basement specialists through separate tendering.
Unfortunately, savings are too often made at the foundation of the house, as is often witnessed. I consider a "black bathtub" (fully waterproof basement shell) on a slope a worst-case nightmare scenario—do not allow that under any circumstances. Weather patterns tend to become more extreme. You are definitely making a sensible investment in the basement if it is constructed to withstand groundwater pressure.
G
Gerddieter29 Jan 2024 10:47Allthewayup schrieb:
The term “WU basement” is often used by builders (mostly non-professionals) as a synonym.
Here, a distinction is made between the precast method (concrete precast elements) which are poured on site with WU concrete (waterproof concrete), and the monolithic construction method, where formwork is created on site and then also poured with WU concrete.
...
Therefore, my advice: for a WU basement, avoid precast construction according to the WU standard; instead, opt for a WU basement built with formwork according to the DIN standard. If this is not contractually specified, it again leaves room for interpretation (financially, long-term risk) by the contractor to the detriment of the client.
Definitely better—but my feeling is that the original poster has already reached an important milestone if they are at all getting a WU basement with this contractor.
The motto: better precast construction than none at all...
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