An ADU builder in Plano is a licensed contractor who designs and constructs accessory dwelling units — detached backyard units, garage conversions, attached additions, and junior ADUs (JADUs). Because an ADU is a complete second dwelling, the builder coordinates foundation, framing, plumbing, electrical, and HVAC work and pulls it through Plano's permit process and utility connections. Not every general contractor has built one, so the right builder is one with ADU-specific experience in Texas.
What ADU Builders Cost in Plano [7][8]
Based on our Plano cost data, expect the following ranges from local ADU builders. Quotes for the same scope typically vary 20-40% between contractors, so getting at least three bids is the single best way to control cost.
| New Detached ADU (all-in) | $140,000-$350,000 |
| Cost per Sq Ft | $250-$400 |
| Garage Conversion | $30,000-$100,000 |
| Prefab / Modular ADU (installed) | $150,000-$300,000 |
| City Permit & Plan Review | 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 |
For a full line-item breakdown, see our Plano ADU cost guide. To confirm what you're allowed to build before you hire, review the Plano ADU rules (max detached size: 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; owner-occupancy: 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).
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How to Vet an ADU Builder in Plano
- License: Confirm a current contractor's license in Texas and that it's in good standing. Ask for the license number and verify it with the state board.
- ADU-specific experience: Ask how many ADUs they've completed in or near Plano and request addresses or photos. ADU permitting and setbacks differ from a kitchen remodel.
- Portfolio & references: Get references from recent ADU clients and, if possible, visit a finished unit.
- Insurance: Verify general liability and workers' compensation coverage. Ask for a certificate of insurance.
- Written, detailed bid: Insist on an itemized, fixed-price or clearly-scoped bid — not a verbal estimate. It should state whether permits (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), 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), and 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) are included.
- Permit handling: Confirm they manage Plano's permit process ("By-right building permit through Plano Building Inspections (972-941-7140) — no rezoning, hearing or special exception. The city's cottage permit handout (FM624RY007A) lists a scaled site plan showing the cottage, its distance to the house and the parking space, elevations, floor plan, engineered foundation and braced-wall design, energy-code compliance, the occupancy affidavit (§15.1800.4.A) and the county-recorded no-separate-sale covenant (§15.1800.4.B), with proof of recording before the permit issues. HOA deed restrictions apply separately", typically Not published — Plano posts no review-time target for residential permits; confirm current plan-review times with Building Inspections (972-941-7140)) and who is responsible if revisions are required.
- Payment schedule: Avoid large upfront payments. A reasonable schedule ties payments to completed milestones.
Questions to Ask Before You Hire
- How many ADUs have you built in Plano in the last two years?
- Is your bid fixed-price, and what would trigger a change order?
- Are permits, plan check, and utility connection fees included?
- What's a realistic timeline, including permit review (Not published — Plano posts no review-time target for residential permits; confirm current plan-review times with Building Inspections (972-941-7140)) and construction?
- Who is my point of contact and how are delays communicated?
- What warranty do you provide on workmanship?
- Can you share three recent Texas ADU client references?
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