I have two slabs in a Home Office converted from a garage.
The regular garage slab and another which is about 6 inch higher than the garage one. The lower one has a wall between the two except for a large door. This wall is seated on a 2x4 timber planks.
When there is very heavy rain, water seeps under that timber in the doorway into the lower garage floor.
I see it seeping in and wondered how I could stop it.
We are on a slight slope down toward the office and have clay just one meter below. I guess it is the water preessure below that is causing it.