Everything homeowners ask about building an ADU in Plano — answered with 2026 data.
Yes, ADUs are allowed in Permitted by right in most residential districts — SF-20, SF-9, SF-7, SF-6, UR, PH, SF-A, 2F, GR, MF-1, MF-2, MF-3, MH and RCD per the residential districts use table (Plano Zoning Ordinance §14.100, endnote 51 → §15.1800). Not permitted in the Agricultural (A) or Estate Development (ED) districts — confirm your parcel's district with Plano Planning in Plano, TX. The maximum size for a detached ADU is 1,100 sq ft, or 50% of the gross habitable floor area of the main dwelling unit, whichever is more restrictive — and not exceeding the maximum lot coverage of the governing zoning district; minimum 400 sq ft (Plano Zoning Ordinance §15.1800.2.D and §15.1800.2.E). Attached ADUs can be up to Not applicable — Plano's Backyard Cottage is defined as a detached dwelling unit. 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 $130,000-$260,000. The cost per square foot averages $150-$275. Garage conversions are more affordable at $60,000-$145,000, while prefab ADUs cost $90,000-$200,000. Permit fees add Building permit and plan review fees are valuation-based — Confirm current amounts with Plano Building Inspections to your budget. See our detailed Plano ADU cost guide.
Detached ADUs in Plano can be up to 1,100 sq ft, or 50% of the gross habitable floor area of the main dwelling unit, whichever is more restrictive — and not exceeding the maximum lot coverage of the governing zoning district; minimum 400 sq ft. Attached ADUs are limited to Not applicable — Plano's Backyard Cottage is defined as a detached dwelling unit. Junior ADUs (JADUs) have a cap of Not a category in Texas — Plano's ordinance has no junior ADU designation. Maximum height is Must not exceed the height of the main residential building (Plano Zoning Ordinance §15.1800.2.B). Note §13.900.1.B.viii separately caps detached accessory buildings located in a required rear or side yard at 10 feet — whether that applies to a Backyard Cottage placed in a required yard is not settled on the face of the code; 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 underlying district's rear yard applies (10 feet in SF-9, SF-7 and SF-6, Plano Zoning Ordinance §9.500-§9.700), and §13.900.1.B.iii allows detached accessory buildings other than garages as close as 3 feet to a rear lot line. Confirm which standard applies to your cottage with Plano Planning. Side setback: §15.1800 sets no cottage-specific side setback — the underlying district's side yard applies (6.5 feet or 10% of lot width, whichever is greater, in SF-7, Plano Zoning Ordinance §9.600.3), and §13.900.1.B.iii allows detached accessory buildings other than garages as close as 3 feet to a side lot line. Confirm with Plano Planning. Front setback: No cottage may stand in front of the main house — detached accessory buildings must be located behind the main building (Plano Zoning Ordinance §13.500.2.P, applied to cottages by §15.1800.3.A). A minimum 10-foot separation from the main dwelling unit is also required (§15.1800.2.F). Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
1 additional off-street space for the cottage (Plano Zoning Ordinance Art. 16 parking schedule), and it may not be satisfied by tandem parking (§15.1800.6.B). Front-yard driveway access is allowed only where it matches the prevailing design on the block, must be shared with the main dwelling, and curb cuts may not exceed 24 feet (§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.
Not required — §15.1800 imposes no owner-occupancy condition, and the city's own fact sheet contemplates renting either the cottage or the main house. What is required instead is a recorded covenant putting future buyers on notice that the cottage cannot be sold separately (§15.1800.4.A). 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 Confirm with Plano Building Inspections (972-941-7140) — no published review timeline for Backyard Cottages found in a city source. Plan check: Standard residential plan review — Confirm timing with Plano Building Inspections. Pre-approved plans availability: No city pre-approved plan library found — Confirm with Plano Planning (972-941-7151).
Average ADU rental income in Plano: 1-bedroom units rent for $1,250-$1,650/month, 2-bedroom units for $1,650-$2,250/month. Short-term rentals: Effectively no in single-family neighborhoods — Plano's short-term rental ordinance treats a Backyard Cottage and the main dwelling as a single residence, and the two cannot be rented as separate Off-site Management STRs (Plano Zoning Ordinance §15.2300.8; Ord. No. 2024-4-13). Off-site Management STRs are permitted only in nonresidential districts and multifamily. Confirm your address with Plano Planning. Expected ROI: 5-8% annual return.
The minimum lot size for an ADU in Plano is 6,000 sq ft (Plano Zoning Ordinance §15.1800.2.A). 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 $60,000-$145,000. 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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