ᐅ Term "Cushion Drainage" – What does it mean?

Hello,
could someone please explain to me what a cushion drainage system is?

Thank you very much in advance

The term “cushion” refers to the frost-protection gravel layer beneath the house’s foundation slab. Around this layer, a full-perimeter drainage pipe can be installed. This pipe is designed to collect water that seeps in (for example, if the property has a slope or adjacent surfaces leading to the house) or groundwater rising up, and either channel it away or allow it to gradually drain into the ground.

However, your civil engineer or groundworks contractor responsible for this construction should be able to explain it to you in detail.