ADUs are allowed in San MarcosTypes:DetachedInternal
Types:DetachedInternal
Accessory Dwelling Unit (ADU) Rules for San Marcos, TX
Is your property eligible for an ADU?
# of Parcels
8,893
Zoning districts
33
Avg Parcel Value
$359,405
Zoning Districts:
8,854 parcels · 33 districts
SF-6
50%(4,462)
SF-4.5
7%(640)
MU
6%(529)
GC
5%(450)
Other
31%(2,773)
ADU Rules
What can you build in San Marcos, TX?
San Marcos, TX follows state and local rules for Accessory Dwelling Units. Here is a concise overview of the local rules.
Eligibility
- –Internal / Attached ADU: By Right
- –Detached ADU: By Right
Interior / Attached ADU Size Limits
- –Maximum size of 1,000 sq ft
- –Maximum size of 50% of the principal dwelling’s habitable area
Detached ADU Size Limits
- –Maximum size of 1,000 sq ft
- –Maximum size of one-half of the principal dwelling's habitable area
Max Units
- –1 ADU (attached or detached) per lot
Owner Occupancy
- –Owner must maintain primary residence on the lot.
Parking
- –2 spaces/ADU (1 per unit + 1 extra); max none; exceptions: on-street credits allowed (not in CD-5D); CD-5D Central Business Area exempt (except new multifamily); CUP for ≤5 units in CD-5/CD-5D; remote/off-site parking within 2,500 ft (1,500 ft elsewhere); tandem parking allowed; parking must be in 2nd/3rd layer.
Rental Restrictions
- –Short-term rentals (<30 days) allowed only if operator is a natural person with a primary residence, holds a valid city STR registration, stays under 30 days, and occupancy is limited to two adults per bedroom plus two additional adults; long-term rentals (30+ days) not prohibited.
ADU State Law
What can you build in Texas?
- –Texas does not have a statewide ADU law. ADUs are regulated entirely at the local level.
- –ADU rules vary significantly by city, and many jurisdictions prohibit ADUs outright.
- –Counties generally lack zoning authority, but other restrictions may still apply outside city limits.
- –Outside city limits, ADU feasibility often depends on subdivision rules, deed restrictions, and septic or fire requirements.
- –Building/fire codes are set statewide, but whether an ADU is allowed is local zoning.
What's allowed on your lot?
These are the municipality-wide rules. What's allowed on a specific property also depends on state laws, setbacks, floor area ratio, lot coverage, environmental constraints, topography, and other property-specific factors. Search your address on FutureLot to see what's allowed on your property.
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ADU rules in other Texas municipalities
Rules change at the town line. Check the municipality your property is actually in.
Hays County