Inspection chamber with unbound slabs

[Peter500]

I'm doing an unbound patio with concrete slabs. I have a recessed inspection chamber and I'm wondering what level to do it. I'm expecting the unbound slabs to sink by approx 2mm, but I suspect, they could sink by a different amount. My chamber lid will be bedded on mortar, so I'm not expecting that to sink.

Should I bed the chamber at the exact same height as the slabs or something different? Think will probably leave the chamber slightly high, which would mean it wouldn't puddle. I'm planning to use a sand/cement mix in the lid, so that will also go hard.

 

[Wayners]

I'm no expert but I say the same as slabs.
Keep it's same height.
You could throw a handful of cement around the drain area in sand as that will help stop any movement.
Worst case you lift slabs and level again as not difficult to fix if its a problem.