Complete 2026 cost breakdown: construction, permits, financing, and expected rental ROI.
Calculate your Richardson ADU cost →Building an ADU in Richardson costs between $120,000-$240,000 for new construction, with per-square-foot costs averaging $140-$265. These figures include design, permitting, site preparation, and construction. The most affordable option is a garage conversion at $55,000-$140,000, while prefab/modular ADUs fall in between at $85,000-$190,000.
| Cost Category | Estimated Range |
|---|---|
| Architectural Plans | $3,000 – $15,000 |
| Permits & Fees | 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 |
| 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. Get up to 5 free quotes from ADU builders serving Richardson — no obligation.
Get Richardson builder quotes →Permit fees in Richardson are Confirm with Richardson Building Inspection (972-744-4180) — the accessory building permit fee schedule is not published on the accessory building page. The review timeline is Confirm with Richardson Building Inspection (972-744-4180) — no published review timeline was found in a city source, and no ADU timeline exists, with 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. Impact fees are Confirm with Richardson Development Services — no ADU-specific impact fee schedule was found in a city source. Pre-approved plans: None — no city pre-approved plan library exists, and none would be usable while ADUs are not a permitted use.
| 1-Bedroom Rent | $1,150-$1,500/month |
| 2-Bedroom Rent | $1,500-$1,950/month |
| Annual Rental Income (est.) | $15,900/year |
| Payback Period (est.) | 11.3 years |
| Short-Term Rental | Moot for an ADU, since none may lawfully exist — but Richardson does regulate short-term rentals of the house itself. Registration is required for any residential property rented wholly or partly for under 30 consecutive days, including a room within the house. Ordinance 4597, passed August 10, 2026, added a 500-foot separation requirement between single-family short-term rentals and raised the annual registration fee from $100 to $300; a property within 500 feet of a registered STR is ineligible. Hotel Occupancy Tax is remitted directly to the city through the registration system from October 1, 2026. Renting for 30 days or more instead requires long-term single-family rental registration |
| Overall ROI Estimate | 5-8% annual return (hypothetical — ADUs are not a permitted use in Richardson) |
A typical ADU in Richardson generates approximately $15,900 per year in rental income based on average 1-bedroom rents. At an average construction cost of $180,000, the estimated payback period is 11.3 years — before accounting for the resale value the ADU adds, which an appraiser determines from comparable sales in Richardson 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 Richardson: $55,000-$140,000.
2. Prefab/modular ADUs offer predictable pricing and faster timelines. Average: $85,000-$190,000.
3. Pre-approved plans — available in Richardson, 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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