Waterproofing shed floor

We recently downsized our house to match our downsized family, and it has a nice little shed out the back, to develop into the retirement haven, when I retire that is. I have started work on the project, however I have a serious problem and am unsure how to attack it.

The brainstrust :doh: that previously owned the house built the shed on an oversized existing slab, hence no overlap of the wall sheets at the bottom of the wall. So whenever it rains water flows in under the sheets and the floor ends up with puddles everywhere and takes weeks to dry out not to mention the water damage to everything on the floor.

I have thought a maybe some sort of wetseal as in a shower recess or maybe a row of hebel blocks around the bottom of the wall. whatever I do I imagine that the bottom of the sheets will start to decay, but if I can waterproof the floor I can live with this.

Does anyone have any suggestions on how to attack this problem

Have a flashing folded up to slip up behind the sheets and overlap the slab.

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