Foundation repair in Round Rock, Texas

The ground under Round Rock

Round Rock sits astride the break between the Grand Prairie and the Black Prairie, and the Balcones Fault Zone is the thing that puts it there. The zone is a series of generally down-to-the-east normal faults which juxtapose Lower Cretaceous rocks on the west against Upper Cretaceous rocks on the east. West of the faulting you are on the southern reach of the Edwards Plateau: thin, rocky soils over limestone, dolomitic limestone, marl and chert, and hard rock close enough to the surface that seasonal moisture cycling has very little soil to work on. East of it you are on the Black Prairie, where thick black calcareous clays overlie Late Cretaceous shales, marls and chalks — the same expansive, montmorillonitic material that moves slabs across the rest of this corridor. The practical consequence is that Round Rock has two distinct foundation problems, and which one you have is a question of geography rather than of how well your house was built.

Soil series mapped here

• Houston Black clay — eastern Round Rock, Black Prairie side
• Branyon clay — eastern Round Rock, Black Prairie side
• Thin residual soils over Edwards limestone — western Round Rock, Grand Prairie side

These are named USDA series. You can look up the ones under your own address for free in the NRCS Web Soil Survey — we would rather you checked than took our word for it.

Which houses are moving, and why

Round Rock has a far longer and more layered build history than the towns further east. The established neighbourhoods — Brushy Creek, Forest Creek, and the original Round Rock West corridor — went up largely through the 1980s and 1990s, and Forest Creek in particular now has genuinely mature trees, which matters because large trees draw moisture out of clay and are a common driver of one-sided movement on the eastern half of town. Around and outside that older core sits a ring of master-planned communities from the 2000s and 2010s: Teravista, Behrens Ranch, Paloma Lake and Siena, the last two on the eastern side near SH 130 and therefore squarely on the clay. Almost everything from the 1990s onward is slab-on-grade, much of the newer stock post-tension. The older 1980s stock is the group worth watching most closely: it has been through every drought cycle since 2011 and its original drainage and grading are now thirty-odd years old.

Neighbourhoods on this soil

• Forest Creek
• Brushy Creek
• Teravista
• Behrens Ranch
• Paloma Lake
• Siena
• Round Rock West
• Old Town Round Rock

What has driven movement here

• The eastern subdivisions near SH 130 — Paloma Lake and Siena among them — were built on Black Prairie clay during the 2000s and 2010s, then hit the 2022 drought at ten to twenty years old. April through July 2022 was the hottest such stretch on record in Texas and much of Central Texas ran rainfall deficits of 11 to 16 inches by early August.

• Dell's headquarters and the employment base around it, reported at over 50,000 jobs inside the city limits, mean Round Rock has an unusually active resale market for a town this size. Foundation questions here surface disproportionately at inspection during a sale rather than because an owner noticed something — which is a different, more urgent, and more negotiable situation than the one most foundation advice is written for.

• The 1980s and 1990s stock in Brushy Creek, Forest Creek and Round Rock West has now been through both the 2011 drought — the driest twelve consecutive months ever recorded statewide — and the 2022 repeat. Thirty-year-old grading, thirty-year-old drainage and thirty-year-old trees are a materially different risk profile from a house finished last year.

Slab repair in Round Rock

The first question on any Round Rock slab is which side of the fault the house is on, because it changes both the diagnosis and the likely method. On the eastern, Black Prairie half, the problem is the familiar one: deep expansive clay, perimeter movement through the seasonal moisture cycle, and pressed concrete pilings as the usual answer. On the western, Grand Prairie half, thin soil over limestone means far less seasonal movement — so genuine settlement there is less common, and when something is moving it is more often a drainage or plumbing-leak problem than soil shrinkage. That distinction matters commercially as well as technically: a homeowner on the west side being quoted a large number of piers for classic clay-shrinkage settlement has a reasonable basis for wanting a second opinion. Mature trees in the older 1980s and 1990s neighbourhoods are a genuine and frequently missed driver of one-sided movement on the clay side, and post-tension slabs across the newer master-planned stock must be located before anyone cuts concrete.

What foundation repair actually costs

Landmarks and boundaries we mean by "Round Rock"

• The I-35 corridor, which runs roughly along the geological transition through town
• Brushy Creek, and the round rock in it that gave the city its name
• SH 130 along the eastern edge, near Paloma Lake and Siena
• Dell's headquarters campus and the employment centre around it
• Old Town Round Rock and the pre-war core around Main Street