Building waterproofing of earth-contacting components

Hello,
we are building a two-story single-family house on a steep slope on the valley side, where the basement is located partly underground at the rear. For illustration, I have attached a picture of the cross-section.


According to an older soil survey, the following statement applies:

Notes on building waterproofing:
Highly used building parts embedded in the soil (basement rooms) must be permanently protected against moisture from the soil. The requirements for waterproofing depend on the moisture exposure. With the new version of DIN 18195-4 published in August 2000, the classification of moisture exposure cases was revised. A distinction is now made between soil moisture, non-ponding seepage water, temporarily ponding seepage water, and pressurized water. The assumption of the "soil moisture" exposure case according to DIN 18195, Part 4, requires very good permeability (kf > 10^-4 m/s) of the natural soil and the backfill in the working space.

Due to the binding character of the soils encountered in the investigation area (clayey soil) and the significantly lower permeability associated with it, it must be expected for buildings with basements that surface water will pond and possibly layer water will accumulate in the working space backfill (so-called "bathtub effect"). In such cases, waterproofing according to DIN 18195, Part 6, is generally required.
If ponding of seepage water in the backfilled working space is prevented by drainage according to DIN 4095, whose functionality is permanently ensured, the floor slab and exterior walls can also be waterproofed in soils with kf less than or equal to 10^-4 m/s according to DIN 18195, Part 4, subject to the following notes:
The surface drainage in front of the wall (e.g. drainage plates made of bitumen-bonded polystyrene beads or drainage mats made of plastic studded sheets) and the ring drainage at the foundation must be installed with suitable quality. This also includes:
- Ensuring a functional outlet
- Construction of a sufficient number of inspection shafts
- Annual check of the drainage’s functionality.

According to the general contractor’s construction description, the following measures are planned:
Horizontal moisture insulation:
- On the concrete floor slab: complete bitumen torch-on membrane G200 S4 Aluminum or “Knauf sealing membrane Katja Sprint” or equivalent.
- Foil membrane / bitumen torch-on membrane under the masonry walls standing on the floor slab against rising moisture.
- Sealing slurry under the concrete walls standing on the floor slab against rising moisture.

Vertical moisture insulation against "non-pressurized water":
On the outside of the earth-contacted, unplastered raw exterior wall surfaces (made of reinforced concrete):
e.g., Ceresit BT21 sealing membrane - all-weather cold self-adhesive bitumen sealing membrane and/or bituminous thick coating; additional filling protection made of sliding foil, studded sheet, filter fleece.
In the base area up to 30 cm above the planned terrain: plasterable sealing slurry.

Drainage pipes:
In the basement / cellar:
● Material: PVC drainage pipe DN 100
● Wrapped with fleece, covered with lava, gravel, etc. as filter layer.
● In the soil on mountain and gable sides.

Questions:
1. Are the planned measures sufficient with regard to the statements of the soil survey?
2. The excavated cohesive soil will rather not be suitable for refilling the working space at the rear, so I have to expect additional costs for refilling with suitable material, right?

Thank you very much

Everything is correct. Yes, gravel or filling sand goes into the excavation pit. No clay. Do not save on the drainage!

Be careful to use the correct drainage pipes. Rigid pipes according to DIN 4095 must be used and not the yellow flexible ones.

The situation is exactly the same for us. Soil, clay excavation, etc. The sealing of the foundation slab is done in the same way as with you. However, the reinforced concrete walls receive a bitumen thick coating for load case 6 (backed-up seepage water).

What I am wondering, though, is whether the clay should actually be used for filling (at least where minor settlements do not matter) to avoid the bathtub effect.

I would suggest that we stay in touch here about how this is resolved...

Hey, thanks to all of you for the answers : Do you mean with your statement that I generally shouldn’t leave them out (I don’t intend to) or is your contribution going in a similar direction as ?

We are building with a general contractor, I will clarify that with him.

yes, that is a very good idea. I have already requested a discussion with my general contractor on the matter. I will report back.
So you mean that due to the installation of the clayey soil, infiltrations shouldn’t occur in the first place?

So you mean that due to the installation of the clayey soil, no infiltration should occur in the first place?

So purely logically: all around the house there is clay and water only infiltrates there slowly. Then you backfill the working space with permeable gravel and the water takes the path of least resistance and you end up with your bathtub. Therefore, I feel (not a professionally qualified opinion) that it is better if the backfilling of the working space does not invite flooding. Unfortunately, clay is apparently difficult to compact, meaning settlement over a longer period must be expected. So you do fill with expensive crushed stone/sand or similar but then have to be very careful about sealing and drainage.

Our current plan is to install a "relief layer" all around on the hillside side. That means gravel wrapped in fleece at the level of the foundation slab. This should allow water to flow around the house. Whether this is the best solution, I do not know...