ᐅ Is a dimpled membrane (used around terraces) necessary?

Hello everyone,

We had our prefabricated house built on a concrete slab. The slab currently extends about 30cm (12 inches) above the ground all around the property.

In the areas where we will be backfilling with soil, we will of course install a dimple membrane (drainage board). But is it also necessary around the terrace area? I have a beam construction (battens/counter battens) with adjustable pedestals standing on the compacted soil from construction. This area will not be backfilled with earth, so the slab will continue to protrude 30cm (12 inches) above the ground and will be exposed to air.

Just as a precaution, I spread 16/32 gravel (instead of soil) here (even though water can drain away in all directions and the slope leads away from the house). I spread about 5cm (2 inches) of gravel over a width of 30cm (12 inches). Should I also install a dimple membrane behind the gravel against the house here?

I only thought about the dimple membrane after I had already emptied the bags...

Thanks in advance.
Best regards,
hausi