ᐅ Are empty conduits and pull boxes in waterproof concrete (WU concrete) a risk?

Hello everyone,

We are currently having an extension built onto the existing building. The extension will have a basement and is also intended to be used as living space. The basement area is largely (except for about 50–70 cm (20–28 inches)) below ground level.

The planned construction includes a studded membrane, 12 cm (5 inches) perimeter insulation, and 24 cm (9.5 inches) waterproof concrete with double reinforcement. (Formed and poured on site). A drainage system is also planned. According to the construction company and the architect, empty conduits and junction boxes should not be an issue.

For safety reasons, should I nevertheless avoid using junction boxes and conduits, or insist on an additional protective layer on the outside? Would a bitumen layer possibly be helpful here?

Best regards

netzplan schrieb:

Should I, just to be safe

Safe regarding what or against what?

How is that supposed to work anyway? You have the formwork—where do you want to install the conduits? And doing it afterward is a huge effort, but you would have 4 cm (1.5 inches) of space. Since 20 cm (8 inches) are sufficient.

nordanney schrieb:

For protection from what or against what?

To prevent water from penetrating from outside, or from the ground. (Although we still have a drainage system.

Bookstar schrieb:

How is that supposed to work? You have the formwork—where do you want to install conduit pipes? And retrofitting is a huge job; but you would have 4 cm (1.6 inches) of clearance. Since 20 cm (8 inches) would be sufficient.

Okay, these deep combination boxes won’t work then, the ones that are 6 cm (2.4 inches) deep.

Would you still recommend applying an additional coating, for example bitumen, to an exterior wall made of waterproof concrete (WU concrete) from the outside? Or would that be counterproductive with waterproof concrete?
(The perimeter insulation will be installed afterwards anyway.)

Cutting grooves into minimally executed waterproof concrete (I believe around 25cm (10 inches) thick) is tricky. You can either make the waterproof concrete thicker by the planned box depth, but then you have to deal with the electrician’s frustration when they have to chisel the grooves there.

Alternatively, you can create an installation layer on the exterior walls using drywall, where the boxes are then installed. Both methods incur costs. Anything else risks compromising the water tightness of the wall.

PS: A cost-effective alternative would be baseboards with attached boxes. Or you could completely avoid boxes and wiring on the exterior walls, or use a combination of surface-mounted wiring and baseboards.

Alternatively, you can install about 4cm (1.5 inches) of Styrodur insulation boards on the interior and then have them plastered. This also allows you to integrate the electrical installation within the layer.