ᐅ Insufficient concrete cover in basement "white tank" construction

Hello everyone,

The structural shell contractor agreed to build a basement using cast-in-place concrete. According to the reinforcement plan from the structural engineer, it concerns a “white tank” (watertight concrete structure). The reinforcement plan specifies the following concrete cover:

• Base slab: 4.0 cm (1.6 inches)
• Basement walls: 3.5 cm (1.4 inches)

The base slab and walls were poured, but the concrete cover on the sides was insufficient. The following was observed:
Reinforced concrete walls at the base area:
On the east side, a minimum cover of 16 mm (0.63 inches), on the west side 14 mm (0.55 inches), and on the south side 7 mm (0.28 inches) was found.

The basement walls will be insulated with 12 cm (4.7 inches) XPS insulation.

The contractor offers the following remedial measures:

• Reactive waterproofing
• Epoxy resin
• Shotcrete

Which option is recommended? Are there any other possible solutions?

The structural contractor obtained the following letter from their own structural engineer, recommending reactive waterproofing:

Confirmation of a So-Called White Tank Dear Mr. XXXXX, The term “white tank” is clearly defined in the DIN standard. Choosing a construction equivalent to a white tank should not pose a problem nowadays. In principle, it is possible to waterproof a concrete basement as a white tank by means of a thick coating. The processing guidelines specified by the respective manufacturer of the thick coating must be followed. The thick coating must be applied over all construction joints: wall-to-wall and base slab-to-wall. Any insufficient concrete cover can be disregarded since it is not structurally relevant and corrosion can be excluded. The manufacturer is solely responsible for the coating’s performance in each individual case. The serviceability of a “so-called white tank” can hereby be considered fulfilled.

Is what the structural engineer states correct?

Best regards