San Marcos Drilled Piers | Kairos Foundation Group

Buyer question

Does my San Marcos commercial project need drilled pier foundations?

San Marcos sits within the Blackland Prairie clay belt that runs north from the Rio Grande through San Antonio, New Braunfels, San Marcos, Austin, and Georgetown to the Red River. On expansive clay, shallow spread footings carry real risk of differential movement as the clay swells and shrinks seasonally. Drilled piers extend past the active moisture-reactive zone into a more stable bearing stratum — the specific depth is set by your geotechnical report, not a citywide rule.

Primary condition

Blackland Prairie clay belt

Permitting authority

City / Hays County (parcel-dependent)

System

Straight-shaft & belled piers

Rebar cage being lowered into a drilled pier shaft

Jurisdiction check

City limits or unincorporated Hays County — confirm before you price.

San Marcos permitting splits by jurisdiction: inside city limits, the City of San Marcos reviews under its own adopted code; outside city limits, unincorporated Hays County reviews under its own baseline. Confirming which applies to your parcel is a first step in preconstruction, before bid pricing assumptions get set.

Local permitting & code

Two code baselines apply, depending on the parcel.

City of San Marcos (city limits)	Has adopted the 2021 IBC via its building code ordinance.
Hays County (unincorporated)	Code baseline references the 2018 International Fire Code, which adopts the 2018 IBC by reference for county-regulated commercial, multifamily, and public construction; single-family/duplex/triplex builders attest to meeting at minimum the 2006 IRC or the version adopted by the relevant city.
Review process	Hays County submittals go through an online plan-review system; confirm current process and timeline directly with the county for unincorporated parcels.

Source

City code: City of San Marcos building code ordinance (official). County code baseline and review process: Hays County Development Services / Plan Review pages (official). Blackland Prairie belt geography: industry summary of Central Texas foundation problems.

Aerial view of a benched hillside excavation on a Central Texas commercial site

Tremie concrete being poured into a cased shaft

Steel casing being set into a bored shaft

FAQ

San Marcos foundation questions, answered directly.

Does San Marcos sit on expansive clay?

San Marcos sits within the Blackland Prairie clay belt that runs from San Antonio through Austin and Georgetown — a geologically clay-dominant corridor. A project-specific geotechnical report is still needed to confirm the plasticity index and pier design for your exact parcel.

Do I permit through the City of San Marcos or Hays County?

It depends on whether your parcel is inside San Marcos city limits or in unincorporated Hays County — the two jurisdictions have different adopted code baselines and review processes. Confirm which applies before setting bid assumptions.

What code edition applies inside San Marcos city limits?

The City of San Marcos has adopted the 2021 IBC via its building code ordinance, effective per the city's own adoption record.

What code baseline applies in unincorporated Hays County?

Hays County's baseline references the 2018 International Fire Code, which adopts the 2018 IBC by reference for commercial, multifamily, and public construction; single-family and small residential builds attest to at least the 2006 IRC.

What should I send for a San Marcos drilled pier bid?

Send current plans, structural drawings, the geotechnical report if available, and the parcel address or plat — the address determines which jurisdiction's code and review process applies.

San Marcos bid invitations

Have a San Marcos project going out for bid?

Send your geotech report and structural drawings — we’ll tell you what a pier schedule for your specific site actually looks like.

Submit a bid invitation

Drilled Pier Foundations in San Marcos, TX