New building with basement | WU concrete plus ring drainage

  • Erstellt am 2021-05-05 10:55:05

Hotdogxxxx

2021-05-05 10:55:05
  • #1
Hello knowledgeable ones,

we are planning the construction of a new house and want to build it with a basement. According to the soil report, the soil consists of impermeable glacial till clay up to a depth of about 5 m. Below that, there is permeable sand. There is no problem with rising groundwater here. However, surface water can be conducted to the basement wall due to the soil. The expert says that the basement could be constructed either with masonry with wall drainage panels or with watertight concrete. For masonry, ring drainage should be used and possibly a soakaway pit installed. When using watertight concrete, according to the report, no drainage is necessary.

The construction company now recommends a masonry basement with waterproofing against pressurized water and perimeter insulation boards. In addition, a ring drainage and a soakaway pit. Alternatively, one could also work with watertight concrete and open water management. In principle, they would still recommend ring drainage with a soakaway pit for the watertight concrete to avoid long-term problems.

The execution of the basement is made more expensive by these measures/recommendations by about €17k for the masonry basement, and with watertight concrete (with open water management) by €7k or watertight concrete (with ring drainage and soakaway pit) by €16k.

Basically, we would rather work with watertight concrete, but the recommendation to still work with drainage makes us suspicious and sounds a bit like a double safety net. The construction company justifies this by the pressurized water and the expected higher humidity in the basement due to capillary action.

Since we are building the house with a central ventilation system, we could quite easily connect the basement rooms to it.

We now have to decide what to do and are somewhat puzzled. What is your opinion on this? Does anyone have experience with watertight concrete and glacial till clay? Is moisture an issue here?

Thank you very much for your opinion.
 

Martial.white

2021-05-05 11:15:51
  • #2
Actually, all of this should be included in the soil report.
 

Harakiri

2021-05-05 11:22:39
  • #3
WU concrete with drainage is basically redundant (provided that the soil survey specifies either/or), but do you really want to save money there? Everything that quickly and safely leads water away from the house is, in my opinion, sensible.

I would first ask why the additional costs? For us (with about 150 sqm of basement) the drainage costs about €2,700.

And the consideration of whether with or without a soakaway shaft is certainly not only because of the basement drainage... where does the rainwater from the roof end up according to the current planning?
 

Hotdogxxxx

2021-05-05 11:32:34
  • #4
Why the additional costs is a good question! According to the cost estimate, the drainage of the partial basement (approx. 50 m²) costs around €4,000 and the soakaway shaft at approx. 6 meters depth an additional €8,000. Since the basement is in the glacial till, drainage without a soakaway shaft doesn't make sense, does it? The water can't drain away.

The water from the roof goes into the sewer system.
 

Jann St

2021-05-06 10:10:58
  • #5
Hi,

I am professionally in constant contact with waterproof concrete elements and have also written my thesis on this topic in civil engineering.
Laying a drainage for this is quite unusual. I also do not consider it sensible - why should I then spend the money on the waterproof concrete element?

However, during planning and execution, care should be taken to ensure that you actually get a waterproof concrete structure and not just a basement with concrete, where the delivery note says "WU". A waterproof concrete basement is much more than just waterproof concrete.

Agree on an execution according to the [WU-Richtline] - accordingly, a waterproof concrete structure must be planned.
If you decide on something like this, involve experts and do not just "blindly" commission a supposed specialist company.
I am also happy to take a look if you need further assistance there.

Best regards, Jann
 

hanghaus2000

2021-05-06 12:11:44
  • #6


Now you’re also taking away the cash cow from the entrepreneur! Why didn’t the entrepreneur factor that in and offer it right away? He knows the construction site.

By the way, I am 100% of your opinion.
 

Similar topics
15.01.2013Soil survey report for house construction10
09.09.2013Costs for soil replacement, soil survey for construction ground, clayey25
09.10.2016Roofing - Clay or Concrete?16
07.09.2017Floor slab: Concrete or wooden beam ceiling - Advantages and disadvantages!?20
20.02.2016Basement made of watertight concrete - switch problem12
22.12.2016Is rain harmful to concrete slabs?12
08.07.2016Concrete under downspout of roof gutters13
13.10.2016Removing tiles from concrete16
10.07.2017WU concrete + flush-mounted boxes in the residential basement - how can this be solved?35
27.08.2017Rust spots on concrete - ceiling to wall - new construction12
29.12.2020Y-Tong vs Concrete without extra insulation in practice (heating costs)38
14.12.2019Connecting Concrete Flush Boxes | DALI Circuit10
30.06.2020Base plate, too little cement in the concrete19
08.07.2020Concrete fence posts widen18
24.03.2021Cracks detected in basement concrete exterior wall, how to proceed?33
17.09.2021Casting concrete paving stones yourself12
05.04.2022Attic roof - wood or concrete cheaper?10
14.04.2022Are there polygonal concrete slabs on the market?13
12.01.2023Prefabricated garages concrete and steel, current prices?21

Oben