On Wednesday, June 10, 2020 at 8:36:51 AM UTC-4, TimR wrote:
On Tuesday, June 9, 2020 at 10:33:36 PM UTC-4, Clare Snyder wrote:

Concrete wicks water. You could just lay heavy tar paper beneath the
wood to prevent that.

Yesterday I found one more reason doing the block wall was a bad idea.

Concrete is porous to water, but not very fast.

We had hurricane Isaias run over our area, and low lying water poured into the shed. In severe rains I've got a bit before, it doesn't drain well from one side of the shed, it's on my list of projects. Anyway, it ran over to my new block wall, which is apparently slightly downhill, and got trapped. In the past it's quickly drained out through the gaps, but now I have concrete block mortared to the slab, and it trapped the water like a swimming pool. I had to drag out the wetvac.