Complete 2026 cost breakdown: construction, permits, financing, and expected rental ROI.
Calculate your Plano ADU cost →Building an ADU in Plano costs between $140,000-$350,000 for new construction, with per-square-foot costs averaging $250-$400. These figures include design, permitting, site preparation, and construction. The most affordable option is a garage conversion at $30,000-$100,000, while prefab/modular ADUs fall in between at $150,000-$300,000.
| Cost Category | Estimated Range |
|---|---|
| Architectural Plans | $3,000 – $15,000 |
| Permits & Fees | 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 |
| Impact Fees | None — Plano's Code of Ordinances has no water, wastewater or roadway impact-fee article, and the $5,691 single-family park fee (Code §16-266(d), Ord. 2025-7-11) does not apply to backyard-cottage permits (§16-264(a)). Expect only permit and trade fees plus any water meter or tap charges |
| Site Prep & Foundation | $10,000 – $35,000 |
| Framing & Structure | $15,000 – $45,000 |
| Plumbing | $8,000 – $20,000 |
| Electrical | $5,000 – $15,000 |
| HVAC | $3,000 – $8,000 |
| Interior Finishes | $15,000 – $40,000 |
Quotes for the same ADU commonly vary 20–40% between builders. We pass your request to up to 5 local builders serving Plano, where we have them — free, no obligation.
Get Plano builder quotes →Permit fees in Plano are 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. The review timeline is Not published — Plano posts no review-time target for residential permits; confirm current plan-review times with Building Inspections (972-941-7140), with 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. Impact fees are None — Plano's Code of Ordinances has no water, wastewater or roadway impact-fee article, and the $5,691 single-family park fee (Code §16-266(d), Ord. 2025-7-11) does not apply to backyard-cottage permits (§16-264(a)). Expect only permit and trade fees plus any water meter or tap charges. Pre-approved plans: None — Plano publishes no pre-approved cottage plan library; each cottage needs its own engineered foundation and braced-wall design (permit handout FM624RY007A).
| 1-Bedroom Rent | $1,350-$2,050/month |
| 2-Bedroom Rent | $1,900-$2,500/month |
| Annual Rental Income (est.) | $20,400/year |
| Payback Period (est.) | 12.0 years |
| Short-Term Rental | Only with a city STR registration — $300 per registration or renewal, $200 for a renewal after an incident-free year (Code §6-738, Ord. |
| Overall ROI Estimate | 5-12% gross rent yield |
A typical ADU in Plano generates approximately $20,400 per year in rental income based on average 1-bedroom rents. At an average construction cost of $245,000, the estimated payback period is 12.0 years — before accounting for the resale value the ADU adds, which an appraiser determines from comparable sales in Plano and varies by market (often less than build cost).
1. Garage conversions save 40-60% vs new construction since the shell already exists. Average cost in Plano: $30,000-$100,000.
2. Prefab/modular ADUs offer predictable pricing and faster timelines. Average: $150,000-$300,000.
3. Pre-approved plans — available in Plano, which can save $3,000-$10,000 in design costs and 2-3 months in review time. See which cities offer pre-approved ADU plans.
4. State grants — California's CalHFA ADU grant (up to $40K) is currently paused; check calhfa.ca.gov/adu for status and your state for active programs.
5. Get multiple bids — ADU contractor pricing varies 20-40% for the same project. We recommend getting at least 3 quotes.
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