Foundation repair in Schertz, the corridor's crossroads town.

The older core has slabs built to lighter standards now 40+ years into the clay's wet-dry cycles; the newer sections have engineered pads whose lot-edge fill seams show up after their first hard droughts. We measure both on the same free terms.

FM 78'S 1950S CORE TO THE FM 3009 AND FM 1103 GROWTH, AVIATION HEIGHTS TO THE CROSSVINE — 20 MINUTES UP I-35 FROM OUR VANCE JACKSON SHOP.

The ground under the Randolph Metrocom

Schertz sits on Blackland cracking clay along the I-35 line.

Schertz spans three counties — its Guadalupe County core around Schertz Parkway, Bexar to the south, and newer growth pushing north into Comal — but the foundation story underneath is consistent: Blackland Prairie cracking clay with high shrink-swell, riding the seasonal wet-dry cycle along the Balcones/I-35 line. Cibolo Creek threads through town and pulls the low-lying, older sections through the widest moisture swings. There's no north-side limestone shelf here to steady a slab edge, so most of what we measure in Schertz is the clay breathing, not a failing foundation.

That makes the diagnosis lot-specific rather than geologic. When one slab moves and the next-door neighbor's doesn't, the difference is usually a downspout dumping at one corner, grading that drifted toward the house, or a tree drawing moisture out of one edge in drought. Drought pulls the exposed edges down; the first hard fall storm re-wets the dried clay and heaves it back unevenly. The free elevation survey is what separates seasonal cosmetic cracking from real, dated movement.

Three eras of housing

A 1950s core, late-'80s tracts, and 2010s master-planned growth — all on the same clay.

Schertz grew from a railroad crossing (incorporated in 1958, named for Sebastian Schertz's 1870s store) into the largest of the Randolph Metrocom cities, and its foundations come in clear generations. The oldest stock sits in Aviation Heights and Scenic Hills near FM 78 and the Randolph flight line — 1950s–'60s slabs poured to lighter, pre-modern standards, now six or seven decades into the clay cycle. Part of Aviation Heights also falls in a mapped 100-year floodplain, so drainage and creek-cycle moisture matter more there than almost anywhere in town. These older homes bring the classic calls: seasonal door sticking and corner cracking after a dry summer.

The next wave — Greenshire (1988) off Roy Richard Drive, Riata (platted 1999, built out around 2015) and Belmont Park near FM 1103, and Northcliffe's golf-course homes off I-35 from the 1980s — sits on better-engineered pads that mostly perform well. The newest growth is master-planned: The Crossvine off FM 1518 from about 2013, Homestead off I-35 north of FM 1103, and Woodbridge along FM 3009. On these young slabs the pattern is timing-driven — pad consolidation plus the first hard drought around years three to seven, right as builder coverage ends, telegraphing as cracks near garage returns where cut-and-fill met native clay. Whatever the era, a dated elevation map is what turns a worry into a specific answer.

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