Planning Drainage and Slope Before We Pour

Summary:

Cesar treats drainage as something decided before the pour rather than corrected afterward. Concrete sheds water rather than absorbing it, so installing a slab immediately changes where rainfall on that part of the property travels. His first rule is that water moves away from the house, never toward a foundation, crawl space, or garage. His second consideration is where the water goes after it leaves the slab, since a poorly planned surface simply relocates a puddle rather than resolving it. The failures he describes are standing water after every rain, runoff directed against the house, and water working under the slab edge year after year — the last of which stays invisible until the concrete begins to move.

Answer:

Where the water goes is something we figure out before we pour, not after. Concrete doesn't absorb water, it sheds it. So the day you put a slab in, you've changed where all the rain on that part of the property is going. If nobody planned that out, it goes somewhere you don't want it going. The first rule is water moves away from the house. Not toward the foundation, not toward a crawl space, not into the garage. Then we look at where it's actually going once it leaves the slab. Is there somewhere for it to go, or are we just moving the puddle from one part of the yard to another part of the yard? The mistakes show up as water standing on the patio after every rain, or water running against the house, or water getting under the edge of the slab and working on that base year after year. That last one you don't see until the concrete starts moving on you.