Get water off the clay
How Far Should Downspouts Drain From a Chattanooga Foundation?
Discharge should leave the footing—not the fascia. On Hamilton County clay, a 2x3 dumping at the corner of the slab is how crawlspaces flood. We flush, upgrade to 3x4 where volume demands it, and bury extensions.
A splash block that ends 18 inches from the wall is not drainage. It is a fountain onto the same clay that already holds water. We want runoff to daylight well away from the foundation, onto grade that falls off, or into a buried line that is actually clear. There is no magic number that fits every lot. A flat East Ridge ranch needs more run than a Signal Mountain grade that already sheds downhill—if the outlet is on the uphill wall, that grade works against you.
2x3 vs 3x4
A 2x3 downspout is the builder default. It clogs at the first elbow. A 3x4 moves about twice the water and matches 6-inch troughs. If we hang 6-inch coil and leave the original 2x3, we have moved the bottleneck. Downspout flush and drainage is the page for that work.
Buried lines
Buried extensions look tidy. They also hide clogs. We only bury what we can flush or access. If an underground run is collapsed, we say so instead of promising a flush that cannot pass. Splash blocks are honest on some lots. Buried 3x4 with a clean daylight is better on clay when the line is sound.
Related: standing water in the trough and sizing the trough itself.