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Hidalgo County, TX Accessory Structures: ADU Rules (2026)

Light Restrictions

Compiled from the official code textEditor Martyn O'NeillLast verified September 2026

ADU rules in Hidalgo County, TX, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.

Key Facts

County ADU zoning: None; counties can't zone
Septic permit: Required (H&S 366)
Development permit: Required before build
Flood zone: Floodplain permit needed
Platting: LGC 232 may apply

ADU Eligibility Quick-Check

An Accessory Dwelling Unit (ADU) is a smaller, independent living unit on the same lot as a single-family home: converted garages, detached cottages, basement or attic conversions, and attached additions all qualify. Most states have streamlined ADU permitting since 2020, but local rules still control size, height, and setback.

Is your lot zoned single-family or multi-family residential?
Does your lot have at least 1,200 sq ft of buildable space?
Is your existing home owner-occupied (in most states this is not required, but some require it for ADU permits)?
Will the ADU stay under your state's size cap (commonly 850-1,200 sq ft for detached)?
Can you provide one off-street parking space (waived in many states within 0.5 mi of transit)?

If you answered 'yes' to most of these, you likely qualify in Texas under recent ADU streamlining laws. The Hidalgo County, TX rules below cover local size, height, and setback requirements.

Summary

Texas counties cannot zone, so unincorporated Hidalgo County has no ADU or second-dwelling zoning ordinance. What does apply to a new accessory dwelling is a septic (OSSF) permit, a floodplain development permit, and subdivision platting through the county Planning Department.

These county ordinances apply to unincorporated areas of Hidalgo County. Incorporated cities within the county may have their own rules that take precedence over county-level regulations.

A person must hold a permit and an approved plan to construct, alter, repair, extend, or operate an on-site sewage disposal system.

Source: Hidalgo County Subdivision RulesView official code

Full Breakdown

Hidalgo County government does not regulate accessory dwelling units through zoning; Texas counties have no general zoning authority, and cities regulate ADUs inside their limits. In the unincorporated county, however, a new dwelling triggers real controls. If the lot is not on a public sewer, an on-site sewage facility (septic) permit is required from the Hidalgo County Environmental Health Division, the TCEQ authorized agent, under Health and Safety Code Chapter 366 and 30 TAC Chapter 285. Any structure needs a county development permit before construction, and a floodplain development permit and elevation certificate if the lot lies in a mapped flood zone. Adding a dwelling may also require a subdivision plat under Local Government Code Chapter 232.

Violations & Fines

Building a second dwelling without a septic (OSSF) permit, a county development permit, or a floodplain permit in a flood zone can bring stop-work action, doubled fees, denial of utility service, and enforcement under the county OSSF order.

Frequently Asked Questions

Does Hidalgo County zone accessory dwelling units?

No. Texas counties have no general zoning power, so the county has no ADU ordinance. A new dwelling in the unincorporated county still needs a septic permit, a development permit, and a floodplain permit where mapped.

What county permit does a new second home need?

An on-site sewage facility (septic) permit from the Hidalgo County Environmental Health Division if not on public sewer, plus a county development permit and, in a flood zone, a floodplain development permit with an elevation certificate.

Sources & Official References

Other rules in Hidalgo County

Noise Ordinances: Quiet HoursFew Restrictions Shed & Carport RulesLight Restrictions Tiny HomesLight Restrictions Garage ConversionsLight Restrictions Noise Ordinances: Decibel LimitsFew Restrictions Noise Ordinances: Vehicle NoiseFew Restrictions Noise Ordinances: Amplified Music & Outdoor SoundFew Restrictions Parking Rules: Commercial & Oversized VehiclesLight Restrictions Parking Rules: Abandoned VehiclesLight Restrictions

All Hidalgo County rules

How Hidalgo County compares: Easiest Cities to Build an ADU·Texas rules heatmap·Compare Hidalgo County to another location·View the Texas accessory structures overview

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ADU Rules in Cities Across Hidalgo County

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