ᐅ Formwork for the foundation slab

Created on: 6 Oct 2025 21:44
G
grunlilie
Hello everyone,

The wooden formwork for the basement slab has been installed. After the insulation was laid, the formwork on the inside is still about 20 cm (8 inches) high. According to the plan, the slab should be 28 cm (11 inches) thick.

Is it normal for the formwork to be lower like this? Will more be added on top? Should I address this with the construction company?

Thank you!
familie_s7 Oct 2025 14:12
Will the foundation slab also be continuously insulated? For this, XPS panels would need to be placed vertically inside the formwork. Is it possible that these might then extend beyond the formwork?
11ant7 Oct 2025 14:54
familie_s schrieb:

Will the foundation slab be additionally insulated along the edges? For this, XPS boards would need to be placed vertically inside the formwork. Could it be that these might then extend beyond the formwork?

That would not reassure me, but rather cause a different concern: the top edge of the formwork would simultaneously be a breaking point for the insulation boards – flowing concrete exerts quite significant pressure.
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M
Molybdean
9 Oct 2025 07:20
And even though it is often done that way.

The waterproofing layer should actually be placed below the insulation, not on top.