Everything homeowners ask about building an ADU in Plano — answered with 2026 data.
Yes, ADUs are allowed in Permitted by right (use-table note 51 → §15.1800) in 13 residential districts — SF-20, SF-9, SF-7, SF-6, UR, PH, SF-A, 2F, GR, MF-1, MF-2, MF-3 and MH — and in the UMU (Urban Mixed-Use) and BG (Downtown Business/Government) districts (Zoning Ordinance §14.100 and §14.200 as amended by Ord. 2019-2-10). Not permitted in the Agricultural (A) or Estate Development (ED) districts; Planned Development (PD) districts follow their own ordinances — check your district at share.plano.gov/zoningmap in Plano, TX. The maximum size for a detached ADU is 400 sq ft minimum; maximum 1,100 sq ft or 50% of the gross habitable floor area of the main dwelling, whichever is more restrictive, and never above the district's maximum lot coverage (§15.1800.2.C–E). The city's permit handout lists 45% total coverage in SF-6, SF-7, SF-9 and 2F with garage and accessory buildings capped at 10% of the lot (25%/10% in SF-20) — confirm current coverage limits with Building Inspections. Attached ADUs can be up to Not applicable — a Backyard Cottage is defined as 'a detached dwelling unit subordinate to and located on the same lot as a Single-Family Residence. Plano has an ADU-friendliness score of 6/10. Check our full Plano ADU rules page for complete zoning details.
ADU construction in Plano typically costs $140,000-$350,000. The cost per square foot averages $250-$400. Garage conversions are more affordable at $30,000-$100,000, while prefab ADUs cost $150,000-$300,000. Permit fees add Set by City Council fee resolution rather than in the Code (Code §6-653 amends UAC §304.2), plus a fire-protection plan-review fee on all construction (§304.2.1); the current schedule could not be read in September 2026 — get the figure from Building Inspections to your budget. See our detailed Plano ADU cost guide.
Detached ADUs in Plano can be up to 400 sq ft minimum; maximum 1,100 sq ft or 50% of the gross habitable floor area of the main dwelling, whichever is more restrictive, and never above the district's maximum lot coverage. Attached ADUs are limited to Not applicable — a Backyard Cottage is defined as 'a detached dwelling unit subordinate to and located on the same lot as a Single-Family Residence. Junior ADUs (JADUs) have a cap of Not a category in Plano or Texas — §15.1800 has no junior-ADU designation. Maximum height is Must not exceed the height of the main residential building (§15.1800.2.B). Whether the general accessory-building height limits of Article 13 also apply to a cottage placed inside a required yard is not stated in §15.1800 — confirm with Plano Planning. You are allowed up to 1 Backyard Cottage per lot on a qualifying lot.
Rear setback: §15.1800 sets no cottage-specific rear setback — the rear-yard rule of your zoning district and the accessory-building placement rules of Article 13 apply. The current Article 9 and 13 text could not be read in September 2026, so confirm your district's rear-yard figure with Plano Planning before designing. Side setback: §15.1800 sets no cottage-specific side setback — the side-yard rule of your zoning district and the accessory-building placement rules of Article 13 apply; confirm the figure for your district with Plano Planning (972-941-7151). Front setback: No cottage may stand in front of the main house — it must sit behind the main dwelling per §13.500.2.P as applied by §15.1800.3.A, with a minimum 10-ft separation from the main dwelling (§15.1800.2.F). Driveway curb cuts (excluding alleys) may not exceed 24 ft, and any front-yard driveway must be shared with the main house (§15.1800.5). Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
1 off-street space per cottage (§16.700 parking schedule, added by Ord. 2019-2-10) on top of the main house's spaces, and it may not be tandem (§15.1800.6.B). Front-yard driveway parking is allowed only where it matches the prevailing design on the block, must be shared with the main dwelling, and curb cuts (excluding alleys) are capped at 24 ft (§15.1800.5). Many cities and states have been relaxing ADU parking requirements in recent years. In California, no additional parking is required for ADUs near transit.
Required as adopted: §15.1800.4.A (Ord. 2019-2-10) says the owner must occupy either the main house or the cottage as a permanent residence, may not collect rent on the owner-occupied unit, and must file a notarized affidavit before the building permit. The city's current fact sheet no longer lists occupancy among its key rules and a 2023 amendment is reported to have changed §15.1800.4, but that text could not be read in September 2026 — confirm with Plano Planning. Note that owner-occupancy rules vary by state law — California and several other states have eliminated this requirement for standard ADUs.
The ADU permit review timeline in Plano is typically Not published — Plano posts no review-time target for residential permits; confirm current plan-review times with Building Inspections (972-941-7140). Plan check: Standard residential plan review under the 2024 International Residential Code as amended by Plano (Code §6-709, Ord. 2025-6-15); Plano's amendments delete the IRC one- and two-family automatic sprinkler section (§6-710), so a cottage needs no fire sprinklers. Fire-protection plan review is a separate fee line. Pre-approved plans availability: None — Plano publishes no pre-approved cottage plan library; each cottage needs its own engineered foundation and braced-wall design (permit handout FM624RY007A).
Average ADU rental income in Plano: 1-bedroom units rent for $1,350-$2,050/month, 2-bedroom units for $1,900-$2,500/month. Short-term rentals: Only with a city STR registration — $300 per registration or renewal, $200 for a renewal after an incident-free year (Code §6-738, Ord. Expected ROI: 5-12% gross rent yield.
The minimum lot size for an ADU in Plano is 6,000 sq ft (§15.1800.2.A; restated on the city's Backyard Cottage fact sheet). This applies to detached ADUs — garage conversions and JADUs may have different or no lot size requirements.
Garage conversions are one of the most popular and affordable ADU options. In Plano, a garage conversion typically costs $30,000-$100,000. The key advantages are lower cost (no foundation work), potential setback exemptions, and faster permitting. Read our complete garage conversion guide.
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