ᐅ Basement waterproofing, watertight concrete (white tank method)
Created on: 17 Oct 2012 07:53
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danielhHello everyone,
I would like to get your expert opinion on the topic of basement waterproofing. We have two offers from different construction companies, and I would appreciate your assessment of which basement waterproofing method against hydrostatic pressure is the better option:
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1. Provider
Formwork for the basement, cast on site with 24 cm (9.5 inches) waterproof concrete, followed by 10 cm (4 inches) XPS insulation. According to the building specifications, execution as a "white tank" system:
The foundation consists of a floor slab at least 25 cm (10 inches) thick, made of waterproof reinforced concrete. Under the slab, a 5 cm (2 inches) concrete blinding layer is applied, with a slip layer of 2 layers of PE foil above it. The basement exterior walls are also cast on site using waterproof reinforced concrete approximately 24 cm (9.5 inches) thick (not exposed concrete). The structural design is based on static requirements, assuming a soil pressure of at least 200 kN/m², as well as soil moisture and temporary backwater from seepage. The special composite of concrete and steel reinforcement ensures high crack resistance, which is crucial for long-lasting durability and extended use of the basement.
Because the basement is constructed as a "white tank," no drainage system is necessary. Additional costs typically associated with a soakaway pit and sump pump are therefore avoided. The basement walls, from the top of the slab to the connection with the perimeter insulation slab, are fitted on the outside with a moisture-resistant 10 cm (4 inches) thick XPS insulation.
Regarding the basement level: All basement rooms receive a moisture barrier according to DIN 18195.
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2. Provider
Supply of sandwich elements, cast on site with waterproof concrete, thickness 30 cm (12 inches).
Unfortunately, I do not have more detailed information here as the building specifications are outdated, and I do not yet have a new version detailing the exact basement construction. According to the advisor, who is also a master mason, his construction would be just as safe as the other provider’s solution.
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What do you think?
I would like to get your expert opinion on the topic of basement waterproofing. We have two offers from different construction companies, and I would appreciate your assessment of which basement waterproofing method against hydrostatic pressure is the better option:
----------------------------------------------
1. Provider
Formwork for the basement, cast on site with 24 cm (9.5 inches) waterproof concrete, followed by 10 cm (4 inches) XPS insulation. According to the building specifications, execution as a "white tank" system:
The foundation consists of a floor slab at least 25 cm (10 inches) thick, made of waterproof reinforced concrete. Under the slab, a 5 cm (2 inches) concrete blinding layer is applied, with a slip layer of 2 layers of PE foil above it. The basement exterior walls are also cast on site using waterproof reinforced concrete approximately 24 cm (9.5 inches) thick (not exposed concrete). The structural design is based on static requirements, assuming a soil pressure of at least 200 kN/m², as well as soil moisture and temporary backwater from seepage. The special composite of concrete and steel reinforcement ensures high crack resistance, which is crucial for long-lasting durability and extended use of the basement.
Because the basement is constructed as a "white tank," no drainage system is necessary. Additional costs typically associated with a soakaway pit and sump pump are therefore avoided. The basement walls, from the top of the slab to the connection with the perimeter insulation slab, are fitted on the outside with a moisture-resistant 10 cm (4 inches) thick XPS insulation.
Regarding the basement level: All basement rooms receive a moisture barrier according to DIN 18195.
----------------------------------------------
2. Provider
Supply of sandwich elements, cast on site with waterproof concrete, thickness 30 cm (12 inches).
Unfortunately, I do not have more detailed information here as the building specifications are outdated, and I do not yet have a new version detailing the exact basement construction. According to the advisor, who is also a master mason, his construction would be just as safe as the other provider’s solution.
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What do you think?
B
Bauexperte17 Oct 2012 10:06Hello,
Usually, most builders consider the loading case "ground moisture according to DIN 18195 Part 4." Therefore, it depends on which "moisture or water conditions" are identified in the soil survey. This necessarily determines whether the basement must be constructed as a “white tank” or as a “brown/black tank.”
What you must absolutely keep in mind is that once the results of the soil survey report are available, the respective DIN standard must be referenced in the contract additions, according to which the basement will be constructed as the required tank structure. This way, you can prevent the builder from resorting to possibly cheaper alternatives. Of course, the basement’s execution must be inspected before backfilling and compacting the soil; ideally, this should be done by an independent, external party – meaning it is always advisable to involve external expertise alongside the construction project.
Kind regards
danielh schrieb:What matters here is not the opinions of forum members – the only important aspect is the written findings of the soil survey report!
I would like to get your expert opinion on the topic of basement waterproofing. We have two offers from different construction companies, and I would like to hear your assessment of which basement waterproofing method against groundwater pressure is the better option: ...
What do you think about this?
Usually, most builders consider the loading case "ground moisture according to DIN 18195 Part 4." Therefore, it depends on which "moisture or water conditions" are identified in the soil survey. This necessarily determines whether the basement must be constructed as a “white tank” or as a “brown/black tank.”
What you must absolutely keep in mind is that once the results of the soil survey report are available, the respective DIN standard must be referenced in the contract additions, according to which the basement will be constructed as the required tank structure. This way, you can prevent the builder from resorting to possibly cheaper alternatives. Of course, the basement’s execution must be inspected before backfilling and compacting the soil; ideally, this should be done by an independent, external party – meaning it is always advisable to involve external expertise alongside the construction project.
Kind regards
Thank you, construction expert, for your opinion. Unfortunately, I don’t have a soil survey for my plot yet, but we will definitely get one done. Unfortunately, due to a “promotion” from the construction company—which is actually quite fair—I have to finalize the contract by the first week of November at the latest, so I won’t have the survey by then. I will definitely ask the construction company again whether they waterproof to T4 or T6 standards. With T6, I would be on the safe side.
I was planning to hire a building inspector for the basement inspection anyway. Do you know how much something like that usually costs?
I was planning to hire a building inspector for the basement inspection anyway. Do you know how much something like that usually costs?
B
Bauexperte17 Oct 2012 11:36Hello,
If you already own the plot, you could consider getting the soil survey done in advance and possibly receive a credit from your provider—if this service is included in their scope. I would never recommend starting construction without a survey!
That depends on whether you arrange for just one inspection or several. Try searching online for the "Federal Association of German Building Experts" or the "Federal Association of Publicly Appointed and Sworn as well as Qualified Experts." Both associations can help you find experts in your area, and you can have an initial discussion about costs with them. As far as I know, this is also possible through the German Energy Agency (Dena).
Best regards
danielh schrieb:
I don’t have a soil survey for my plot yet, but we will definitely get one done.
If you already own the plot, you could consider getting the soil survey done in advance and possibly receive a credit from your provider—if this service is included in their scope. I would never recommend starting construction without a survey!
danielh schrieb:
I was already planning to hire a building inspector for the basement acceptance. Do you know how much that usually costs?
That depends on whether you arrange for just one inspection or several. Try searching online for the "Federal Association of German Building Experts" or the "Federal Association of Publicly Appointed and Sworn as well as Qualified Experts." Both associations can help you find experts in your area, and you can have an initial discussion about costs with them. As far as I know, this is also possible through the German Energy Agency (Dena).
Best regards
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