A four-times-renamed farm settlement, mostly new basements
The settlement that became Avon was called Hampton, then White Lick, Smootsdell, and New Philadelphia before settling on its current name, and stayed primarily agricultural well into the twentieth century — Avon didn't incorporate as a town until 1995. That means most Avon basements are recent construction, built into the same clay-heavy Hendricks County soils that shape drainage decisions across the whole Carmel area.
Older farm lots still carry legacy basement construction
The oldest farm properties near Avon's original Washington Township settlement pattern — dating back to the area's post-Civil-War agricultural period — can still have basement or crawlspace construction that predates any of the town's more recent subdivision-era drainage standards, worth checking before assuming a newer fix will apply.