How much does it cost to build a 800 sq ft ADU in Pomona?

Richard Wilson

October 22, 2025 at 05:31 AM

Cost & Budget Pomona, CA

I'm planning to build an 800 sq ft ADU in my backyard in Pomona, California, and I've been trying to wrap my head around the potential costs. My property sits on a half-acre lot, so I have enough space, but I'm working with a tight budget and need to make sure this is a feasible project before diving in. I've read that construction costs can vary significantly, but I'm hoping to get a clearer picture of what to expect in the Pomona area specifically.

From what I've gathered, costs can range anywhere from $100,000 to $300,000, depending on a variety of factors, but I'm curious about more precise figures. For those of you who have recently gone through this process in Pomona, what was your total cost, and how did you manage your budget?

Additionally, are there specific local regulations or fees I should be aware of that might impact the overall cost? I’ve heard that permitting and impact fees can add up quickly, but I’m unclear on the actual figures for our city.

Lastly, I’d love advice on whether it's more cost-effective to go with a prefabricated unit or opt for a custom build. I'm leaning towards something that offers long-term durability and low maintenance, but I’m open to suggestions.

Any insights or experiences would be greatly appreciated, especially any tips on keeping costs down without compromising on quality!

1 Answer

Amanda

October 21, 2025 at 07:12 AM

Building an 800 sq ft ADU (Accessory Dwelling Unit) in Pomona, California is a strategic investment, especially given the city's increasing demand for housing and the flexibility ADUs offer. Let's break down the process, focusing on costs, local regulations, and practical advice to keep your budget in check.

### Cost Breakdown

**1. Construction Costs:**
In Pomona, construction costs for an ADU can range significantly. For a standard 800 sq ft ADU, expect a starting cost of approximately $150,000. This estimate can rise to $250,000 or more, depending on your choice of finishes, the complexity of design, and unforeseen site-specific challenges. Here's a quick breakdown:

- **Basic Construction**: $150,000 to $200,000
- **Foundation**: $10,000 - $15,000
- **Framing**: $20,000 - $30,000
- **Roofing**: $8,000 - $12,000
- **Interior Finishes** (flooring, paint, cabinetry): $25,000 - $40,000
- **Utilities** (plumbing, electrical): $20,000 - $35,000
- **Permits and Fees**: $5,000 - $10,000

**2. Permitting and Impact Fees:**
Pomona, like many Californian cities, has streamlined the ADU approval process thanks to state laws like SB-9 and AB-68 which make it easier to add second units. However, you should prepare for:

- **Permit Fees**: Typically $3,000 to $5,000. This covers plan checks, inspections, and the building permit itself.
- **Impact Fees**: Many cities have reduced these fees for ADUs under 750 sq ft, but since you plan an 800 sq ft unit, you might still incur some charges. Contact Pomona's Planning Department for specifics.

### Local Regulations

- **Setbacks**: Pomona generally requires a minimum setback of 4 feet from property lines for ADUs.
- **Height Limits**: Detached ADUs can typically be up to 16 feet tall.
- **Parking**: Generally, no additional parking is required if the ADU is within half a mile of public transit, which often is the case in urban Pomona areas.

### Prefabricated vs. Custom Build

**Prefabricated Units:**
- **Pros**: Typically more affordable, faster to construct, and offer predictable costs.
- **Cons**: Limited in customization, and transportation costs can add up.
- **Cost**: Starting around $100,000 for the unit, plus site preparation and installation costs.

**Custom Builds:**
- **Pros**: Fully customizable to match your home and preferences.
- **Cons**: More expensive and time-consuming.
- **Cost**: As mentioned, $150,000 to $250,000, depending on complexity.

### Cost-Saving Tips

1. **Design Simplicity**: Opt for a simple design with a rectangular shape to minimize construction complexity and costs.
2. **Standardized Fixtures**: Use off-the-shelf fixtures and finishes to avoid custom manufacturing costs.
3. **Energy Efficiency**: Incorporate energy-efficient appliances and solar panels to reduce long-term utility costs. California offers incentives that can help offset initial costs.

### Timeline

Expect a timeline of 9 to 12 months from planning to completion. This includes:

- **Design & Permitting**: 2-3 months
- **Construction**: 6-9 months, depending on weather and complexity.

### Next Steps

1. **Consult with a Local Architect or Contractor**: They can offer insights specific to Pomona and help refine your budget.
2. **Visit Pomona's Planning Department**: Understand all local requirements and get a clear picture of the permitting process.
3. **Explore Financing Options**: Consider home equity loans or statewide ADU financing programs to support your budget.

### Resources

- **Pomona Planning Department**: [Pomona City Hall](https://www.ci.pomona.ca.us/)
- **California Department of Housing and Community Development ADU Guide**: [HCD ADU Guide](https://hcd.ca.gov/)
- **Local ADU Builders**: Look for reviews and recommendations on platforms like Yelp or Angie's List to find reputable builders in your area.

Building an ADU is an exciting venture that can significantly enhance your property's value and utility. By doing your homework and planning carefully, you can manage costs effectively while creating a space that meets your needs and complements your lifestyle. Good luck with your project!

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Types of ADUs in Pomona, CA

Understanding the different types of Accessory Dwelling Units can help you choose the best option for your property and needs.

Detached ADU

A separate, standalone structure built on your property. Offers maximum privacy and flexibility for tenants.

Complete privacy
Custom design options
Higher rental income potential

Attached ADU

An addition to your existing home with a separate entrance. Cost-effective option with shared utilities.

Lower construction costs
Shared utility connections
Family-friendly proximity

Garage Conversion

Convert existing garage space into a livable unit. Most cost-effective ADU option with fastest approval.

Lowest construction cost
Faster permitting
Uses existing structure

JADU

Junior ADU created within the existing home. Maximum 500 sq ft with efficiency kitchen and shared utilities.

Minimal construction
No parking requirement
Perfect for family use

Upper Floor ADU

Add a second story or convert existing upper floor space. Maximizes property value and rental potential.

Premium rental rates
Enhanced privacy
Great city views

Basement ADU

Convert basement or lower level into living space. Great option for properties with existing below-grade areas.

Uses existing space
Natural temperature control
Sound isolation

ADU Cost Guide for Pomona, CA

Understanding ADU costs helps you budget effectively and make informed decisions about your project. Costs vary based on size, complexity, and local factors.

ADU Type	Size Range	Cost Range	Timeline	Best For
Garage Conversion	400-800 sq ft	$80K - $150K	3-6 months	Budget-conscious homeowners
JADU	Up to 500 sq ft	$50K - $100K	2-4 months	Family use, minimal disruption
Attached ADU	600-1,000 sq ft	$120K - $200K	4-8 months	Shared utilities, family proximity
Detached ADU	600-1,200 sq ft	$150K - $300K	6-12 months	Maximum rental income
Two-Story ADU	800-1,500 sq ft	$200K - $400K	8-15 months	Maximizing property value

Cost Factors to Consider

Site Preparation: $5K - $25K
Permits & Fees: $3K - $15K
Utility Connections: $5K - $20K
Finish Level: $10K - $50K variance
Landscaping: $2K - $10K

Potential ROI

Rental Income: $1,500 - $4,000/month
Property Value Increase: 20-30%
Payback Period: 8-15 years
Tax Benefits: Depreciation allowances
Equity Growth: Long-term appreciation

Get Your Personalized Cost Estimate

These are general ranges. Your actual costs may vary based on specific site conditions, design choices, and local market factors in Pomona.

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Why Build an ADU in Pomona?

Financial Benefits

Rental Income: Generate $18,000-$48,000 annually

Property Value: Increase home value by 20-30%

Tax Benefits: Depreciation and expense deductions

Investment: Strong ROI in California markets

Lifestyle Benefits

Multigenerational Living: Keep family close while maintaining privacy

Home Office: Create dedicated workspace or studio

Guest Space: Comfortable accommodations for visitors

Sustainability: Increase housing density efficiently

Popular ADU Floor Plans

Explore our most popular ADU designs that work well in Pomona, CA. These professionally designed floor plans optimize space and functionality while meeting local building requirements.

Cascade ADU Floor Plan - 2 Bedroom, 2 Bathroom

2 Bed 2 Bath 1,200 sq ft

The Cascade

Spacious 2-bedroom design perfect for families. Features open living area, full kitchen, and two full bathrooms with optimal privacy.

Open floor plan
Master suite
Laundry room

Summit ADU Floor Plan - 2 Bedroom, 2 Bathroom

2 Bed 2 Bath 950 sq ft

The Summit

Efficient 2-bedroom layout maximizing every square foot. Great for narrow lots with smart storage solutions throughout.

Compact design
Pantry storage
Two full baths

Brookside ADU Floor Plan - 2 Bedroom, 2 Bathroom

2 Bed 2 Bath 1,400 sq ft

The Brookside

Luxurious 2-bedroom design with premium features. Includes master suite, guest bedroom, and spacious living areas.

Large living room
Walk-in closets
Full kitchen island

Sequoia ADU Floor Plan - 3 Bedroom, 2 Bathroom

3 Bed 2 Bath 1,100 sq ft

The Sequoia

Unique 3-bedroom configuration perfect for larger families. Features dual bathrooms and smart space utilization.

Three bedrooms
Laundry room
Multiple closets

Crestline ADU Floor Plan - 3 Bedroom, 2 Bathroom

3 Bed 2 Bath 1,500 sq ft

The Crestline

Premium 3-bedroom layout with maximum comfort. Features spacious bedrooms, walk-in closets, and luxury finishes.

Primary suite
Pantry space
Open concept

Ready to Explore More ADU Designs?

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Types of ADUs in Pomona, CA

Understanding the different types of Accessory Dwelling Units available in Pomona, CA can help you choose the best option for your property and budget.