Foundation Slab Poured – Costs, Structure, and Function

From a distance, we can already see the construction crane towering over the neighborhood. And up close, it’s clear: a lot has happened since our last visit two weeks ago. The foundation slab is now in the excavation pit, and the formwork for the first walls is already in place.

Sewer Works

The sewer works are not yet fully completed, but progress is being made. The shell construction team has installed two inspection shafts: one for wastewater and one for rainwater – as part of a so-called separate system. They also built a drop structure to safely bridge differences in pipe elevation.

Foundation Slab

The biggest change is immediately visible: the foundation slab has been poured! And the first formwork for the basement’s exterior walls is standing on it. For the first time, we can sense the dimensions of our house and walk through it room by room.

Structure of the Foundation Slab

The foundation slab consists of several layers to meet both structural and energy efficiency requirements:

• 25 centimeters of waterproof concrete for the slab
• double-layer foil
• 12 centimeters of Styrodur thermal insulation
• 5 centimeters of blinding layer made of concrete
• 1 meter of compacted gravel for soil replacement

Within the blinding layer around the foundation slab lies a ring earth electrode. It is part of the lightning protection system and ensures the electrical safety of the house.

In some cases, a foundation earth electrode made of flat steel embedded directly into the foundation slab is sufficient. However, in insulated buildings, the necessary contact between the concrete and the soil is missing. Since both our foundation slab and basement exterior walls are insulated, an additional grounding system is required: the ring earth electrode.

The ring earth electrode runs outside the building and is therefore permanently exposed to soil moisture. To prevent rapid corrosion, it must be made of highly corrosion-resistant stainless steel (V4A). It is connected to the foundation earth electrode in the slab through multiple bonding conductors.

The foundation earth electrode is in turn connected to the equipotential bonding conductor, which will later be located in the utility room near the circuit breaker panel and is already protruding from the slab. From there, the electrician will later establish the grounding for the electrical systems.

The slab contains four floor outlets for wastewater, which direct the sewage to the inspection shaft. This shaft will also be located in the utility room. It has a cover and is part of the backwater protection system using a Pumpfix. This ensures that wastewater can still drain even during flooding. Another advantage of the inspection shaft: it is easily accessible for maintenance and inspections.

Costs of the Foundation Slab