Paving on existing concrete - advice on some unusual circumstances

[mejones]

We have a small flat area next to our house. It’s fully enclosed - house on one side, retaining walls on three others. Max dimensions are approx 4.5x1.5m, but there’s a protrusion of approx 1m bringing the width to 0.5m in the middle.

The base is a 300mm reinforced concrete slab and it’s continuous with the retaining walls and house foundations. So we don’t want to dig it up. It’s also (currently) fairly new and in good condition.

The only drainage is a gulley in one corner, away from the house. Unfortunately, it was built without a fall.

We would like to pave the area in a way that (i) protects the concrete slab in so far as possible and could (in the future) be removed without causing significant damage to the slab, and (ii) creates a sufficient fall for drainage to the gulley.

No issues with damp proof levels (there is sufficient clearance). The area is light traffic (foot only).

I think, therefore, that we ideally want some sort of waterproof surface on top of the existing slab.

I’ve looked at various options and am unclear on the best way to about this. The block paving over existing base courses page on the pavingexpert site seems relevant, although is focused on higher traffic areas. There is also some helpful advice on the “paving over an existing surface” page, bed it does not really get into the question of drainage for the sort of surface we have.

For example:

* Screed or a 10:1 bedding mix to form a fall, a surface mounted gully on the long side (and perhaps another one on the short side), and then stone flags or porcelain paving on top.

* Some sort of horizontal drainage composite or membrane, with a floating screed on top and porcelain pavers resting on plinths?

More than happy to get a pro in but struggling to find someone who knows their stuff (South London based) and is interested in a job this small.

Any advice would be massively appreciated!