Construction of a base slab with frost skirt but without foundation

Hello,

Always thought that frost skirts end flush with the edge of the slab???

For shallow foundations, that is, buildings without basements, a frost skirt is poured around the slab. The reason for this is to prevent water from flowing under the slab and then freezing into ice in winter, which would lift the slab. The skirt is either shuttered and poured or directly poured into an earth trench. It usually consists of lean concrete and a clean gravel layer.

Kind regards

I want a 60mm thick Styrodur insulation under the base slab.

.. please, for what purpose? ... are you absolutely absolutely absolutely sure that no moisture will later soak through this insulation?

.. please why? ... are you absolutely absolutely absolutely sure that no moisture will later soak this insulation?

With proper planning and execution, insulation below the footing is not a problem. From a building physics perspective, it is even correct.

Hello,

another related question on the topic of frost:

Do the pipes for media carriers such as water, wastewater, etc. necessarily have to be routed downwards through the floor slab and then outwards to be frost-proof, or is it also possible through the wall or where the wall and floor slab meet and then downwards?

Reasoning BU for the variant through the wall: "Then the entire floor slab does not have to be broken up if something is leaking."

Regards

Project 2012

Hello,
in 2011 we founded our house (12x11.5m) as follows due to the soil surveyor (clayey soil, swelling and shrinking possible -> possible building damage):
- Geotextile of GRK 3
- at least 30cm gravel subbase to achieve the required "bedding modulus", compaction must be proven by plate load tests
- 10cm Floormate 500-A
- 30 cm rigid concrete slab made of WU concrete
(then we waived the sealing of the slab with tar paper(!), since WU concrete of this thickness does not allow anything to pass through anyway)
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Our garage had to be founded separately (strip foundations) (even though the architect initially planned it differently (continuous)...) in order to
a) avoid thermal bridges and to
b) obtain a clean boundary closure (the gravel must protrude at least 30 cm at the rigid slab and maintain a certain slope)
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Important: The grounding must be led out of the now well-insulated slab!!
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The insulation cost over 4k€, but we also saved money on sealing.
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The exterior walls are made of Poroton, inside of KS bricks, all without insulating bricks on the base slab.
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Floor structure ground floor: 20cm (underfloor heating), of which 10cm insulation
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Why all this??
No one could initially answer that directly, but we educated ourselves and came to the following conclusion:

Energy savings:
Nice and good, if you use the calculation examples on the web, insulation under the slab never really pays off anyway.
Last winter I had not yet completed the surrounding perimeter insulation on the slab (at the house entrance I still had to pour a foundation for the step) and lo and behold: the facade was ice cold, only at the open spots of the concrete slab was the concrete nice and warm. Certainly quite a bit of heat is lost there because the whole slab is heated even though there is 10cm insulation inside!

What is interesting, however, is the dew point formation!
By insulating under the slab, the dew point is now shifted further outward.
That means mold formation on the floor area can now be almost ruled out. That might not be so bad for us (solid construction), but is certainly less than optimal for timber frame construction.
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I hope this info from a construction layman helps with further decisions.