An ADU builder in Richardson 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 Richardson'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 Richardson [7]
Based on our Richardson 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) | $120,000-$240,000 |
| Cost per Sq Ft | $140-$265 |
| Garage Conversion | $55,000-$140,000 |
| Prefab / Modular ADU (installed) | $85,000-$190,000 |
| City Permit & Plan Review | Confirm with Richardson Building Inspection (972-744-4180) — the accessory building permit fee schedule is not published on the accessory building page |
| Impact Fees | Confirm with Richardson Development Services — no ADU-specific impact fee schedule was found in a city source |
For a full line-item breakdown, see our Richardson ADU cost guide. To confirm what you're allowed to build before you hire, review the Richardson ADU rules (max detached size: N/A — a detached second dwelling is not a permitted use. A detached accessory building is capped instead: all detached structures together, garages included, may occupy no more than 8% of the lot area and may not exceed 40% of the floor area of the principal residence (Art. IV, Sec. 4(d)(2); Art. VII, Sec. 4(d)(2)). Servants' quarters, the only accessory living space allowed, may not have kitchen facilities or separate utility connections (Art. I, Sec. 2); owner-occupancy: Moot for ADUs, since none may be built. Servants' quarters must be occupied by persons employed full-time on the premises as domestic help by the occupant of the premises, and may not be rented (Art. I, Sec. 2). Renting rooms inside the house is allowed to a maximum of two individual renters or tenants (Art. IV, Sec. 1(j))).
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How to Vet an ADU Builder in Richardson
- 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 Richardson 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 (Confirm with Richardson Building Inspection (972-744-4180) — the accessory building permit fee schedule is not published on the accessory building page), plan check (Scaled drawings are required for any accessory building over 150 sq ft, and each exterior wall of an accessory building over 150 sq ft must be at least 35 percent masonry (Art. IV, Sec. 2(b)(2)). Richardson has adopted the 2021 International Codes and the 2020 National Electrical Code. All contractors must be registered with the city before work starts), and impact fees (Confirm with Richardson Development Services — no ADU-specific impact fee schedule was found in a city source) are included.
- Permit handling: Confirm they manage Richardson's permit process ("There is no ADU permit in Richardson, because there is no ADU use to permit. A homeowner wanting a second unit would need a zoning change — most realistically a PD planned development district, where the permitted uses and the height and area regulations are written for the individual tract (Art. II, Sec. 1). That is a City Plan Commission and City Council process, not a counter application. For an ordinary accessory building, a building permit is required for any structure over 40 sq ft; structures of 150 sq ft or less need an application with a sketch, and anything larger needs scaled drawings (City of Richardson Building Inspection, Accessory Building)", typically Confirm with Richardson Building Inspection (972-744-4180) — no published review timeline was found in a city source, and no ADU timeline exists) 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 Richardson 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 (Confirm with Richardson Building Inspection (972-744-4180) — no published review timeline was found in a city source, and no ADU timeline exists) 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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