ADU Rules: Cedar Park vs Round Rock
How do adu rules rules compare between Cedar Park, TX and Round Rock, TX?
Round Rock has fewer restrictions than Cedar Park.
Cedar Park, TX
Williamson County
Cedar Park permits accessory dwelling units (ADUs) only as a conditional use in four large-lot residential districts and only for use by the principal-dwelling owner's immediate family or authorized employees. Detached ADUs must be 400-650 gross sq ft; attached ADUs may not exceed 200 sq ft or 25% of the conditioned area of the principal dwelling, whichever is less.
View full Cedar Park rules →Round Rock, TX
Williamson County
Round Rock permits accessory dwelling units (ADUs) in certain residential zoning districts subject to size, design, and owner-occupancy requirements under the Zoning Code.
View full Round Rock rules →Key Facts Comparison
| Fact | Cedar Park | Round Rock |
|---|---|---|
| Permit required | Yes — conditional use permit + building permit | - |
| Detached ADU size | 400-650 gross sq ft | - |
| Attached ADU size | Max 200 sq ft or 25% of principal dwelling | - |
| Allowed districts | DR, ER, E, SR only (not SU) | - |
| Max per lot | 1 ADU | - |
| ADU Permitted | - | Yes — in qualifying districts |
| Size Limit | - | Percentage of main dwelling or cap |
| Owner-Occupancy | - | May be required |
| Separate Sale | - | Not permitted |
| Permits Required | - | Building, electrical, plumbing |
Highlighted rows indicate differences between cities.
Cedar Park FAQ
Can I build a detached ADU in my Cedar Park backyard?
Only if your lot is zoned Development Reserve (DR), Estate Reserve (ER), Estate Residential (E), or Suburban Residential (SR), and only after obtaining a conditional use permit. ADUs are not allowed in the smaller Semi-Urban Residential (SU) district where most newer single-family neighborhoods sit.
What's the size limit for an ADU in Cedar Park?
Detached ADUs must be at least 400 sq ft of livable area, no more than 600 sq ft of first-floor area, and no more than 650 gross sq ft. Attached ADUs are capped at 200 sq ft or 25% of the principal dwelling's conditioned space, whichever is less.
Does Texas state law override Cedar Park's ADU rules?
Not yet. Statewide ADU preemption bills (e.g., SB 673 in 2025) have been filed but, as of 2025, Cedar Park's local code remains the operative authority. The Planning & Zoning Commission has elected to await state action before amending Article 11.04.
Round Rock FAQ
Can I build an ADU on my property in Round Rock?
Round Rock permits accessory dwelling units (ADUs) in certain residential zoning districts subject to size, design, and owner-occupancy requirements under the Zoning Code.
What are the size limits for an accessory dwelling unit in Round Rock?
ADU Permitted: Yes — in qualifying districts. Size Limit: Percentage of main dwelling or cap. Owner-Occupancy: May be required. Separate Sale: Not permitted.
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