ADU · Costs
How Much Does an ADU Cost in the Inland Empire?
Transparent pricing from a licensed IE general contractor. No surprises.
Starting From
$200,000 — All-In
Most Inland Empire ADU projects range from $200,000 to $435,000 depending on size, site conditions, and finish level.
Cost Breakdown
Cost To Build a New Detached ADU
Inland Empire, California
| Type | Size | Vertical Build Cost | Build Cost/sqft | Typical All-In Cost | All-In/sqft |
|---|---|---|---|---|---|
| Studio / 1BA | 400 sq ft | $150K | $375 | $200K | $500 |
| 1BR / 1BA | 500 sq ft | $175K | $350 | $235K | $470 |
| 1BR / 1BA | 650 sq ft | $210K | $323 | $275K | $423 |
| 2BR / 1BA | 750 sq ft | $233K | $310 | $300K | $400 |
| 2BR / 2BA | 900 sq ft | $270K | $300 | $345K | $383 |
| 2BR / 2BA | 1,000 sq ft | $295K | $295 | $375K | $375 |
| 2BR / 2BA | 1,200 sq ft | $348K | $290 | $435K | $363 |
*Vertical build cost covers framing, roofing, insulation, drywall, windows, doors, electrical, plumbing, HVAC, and standard finishes. All-in cost adds design, engineering, permits, sitework, and utility connections.
What's Included
Inside your all-in cost.
📐
01
Design & Engineering
$8,000 – $12,000
Architectural plans, structural engineering, and Title 24 energy compliance.
🏛️
02
Permit Fees
Varies by city
Impact fees waived for ADUs under 750 sq ft. Larger units: $2–8/sq ft depending on city.
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03
Sitework & Grading
$15,000 – $40,000
Foundation prep, grading, and drainage. Flat lots cost less. Sloped lots cost more.
🔌
04
Utility Connections
$5,000 – $25,000
Water, sewer, and electrical connections to existing services. Long runs cost more.
🏗️
05
Vertical Construction
$290 – $375/sq ft
Full stick-built construction including all systems and standard finishes.
🚿
06
Finishes & Fixtures
Included in vertical cost
Standard package included. Premium upgrades available at additional cost.
Compare
Garage conversion vs new construction.
| Garage Conversion | New Construction | |
|---|---|---|
| Cost range | $80,000 – $150,000 | $200,000 – $435,000 |
| Timeline | 3–5 months | 6–10 months |
| Permits | Simpler | Full permit set |
| Size limit | Existing garage size | Up to 1,200 sq ft |
| Best for | Budget-conscious | Maximum rental income |
FAQ
Questions, answered.
Flat lots need minimal grading. Sloped lots require retaining walls, extra excavation, and engineered foundations — all of which add to sitework cost.
The farther your ADU sits from existing water, sewer, and electrical service, the longer the trenching runs — and the higher the connection cost.
Each Inland Empire city sets its own permit and plan-check fees. Units under 750 sq ft are exempt from impact fees under California law; larger units pay roughly $2–$8 per sq ft depending on the jurisdiction.
More square footage and more bedrooms mean more framing, plumbing, and electrical. Cost per square foot actually drops as size increases, but total cost rises.
Our all-in pricing includes a quality standard finish package. Premium cabinetry, countertops, flooring, and fixtures are available at additional cost.
A standard slab-on-grade is the most economical option. Raised foundations, caissons, or grade beams on difficult soils add cost.
Tight side yards or limited street access can require smaller equipment, hand-digging, or crane work — which adds labor and time to the build.
Get An Estimate
Every project is unique.
These are typical ranges based on current Inland Empire market conditions as of 2026. Schedule a free feasibility consultation to get a detailed estimate for your specific property.