What is the maximum ADU size allowed in Walnut?

Detached ADUs in Walnut can be up to 1200 square feet.

ADU Builders & Contractors in Walnut, CA

Q: How much does it cost to build an ADU in Walnut?

The average cost ranges from $147,000 to $322,000, or $197-372 per square foot.

Q: How long does it take to get an ADU permit in Walnut?

The permit process typically takes 60 to 120 weeks in Walnut.

Walnut, CA is home to 145 ADU contractors ready to help. From initial permits to final inspection, these local professionals know Walnut's building codes and can guide your project from concept to completion.

📊 ADU Quick Facts for Walnut

Avg. Cost/sqft

$197-$372

Permit Timeline

60-120 weeks

Max Size

1200 sqft

Setbacks

4ft sides

Top 145 ADU Contractors in Walnut

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#1J AIRCON INC

Walnut, CA

J Aircon Inc — licensed ADU contractor in Walnut, CA. Detached ADU construction.

View Profile 📞 (626) 890 9109

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#2UNITED INDUSTRIAL CONTRACTORS

Walnut, CA

United Industrial Contractors — licensed ADU contractor in Walnut, CA. Detached ADU construction. 32+ years experience.

View Profile 📞 (909) 978 1200

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#3SUNG PACIFIC INC

Walnut, CA

Sung Pacific Inc — licensed ADU contractor in Walnut, CA. Detached ADU construction. 37+ years experience.

View Profile 📞 (818) 416 8439

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#4TSAI MASTERBUILDERS

Walnut, CA

Tsai Masterbuilders — licensed ADU contractor in Walnut, CA. Detached ADU construction. 41+ years experience.

View Profile 📞 (909) 319 9383

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#5Z R SQUARE CONSTRUCTION

Walnut, CA

Z R Square Construction — licensed ADU contractor in Walnut, CA. Detached ADU construction. 6+ years experience.

View Profile 📞 (626) 616 1151

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#6MJX CONSTRUCTION INC

Walnut, CA

Mjx Construction Inc — licensed ADU contractor in Walnut, CA. Detached ADU construction.

View Profile 📞 (626) 376 6932

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#7ECHEVERRIA FRANCISCO

Walnut, CA

Echeverria Francisco — licensed ADU contractor in Walnut, CA. Detached ADU construction. 18+ years experience.

View Profile 📞 (909) 525 3126

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#8TUNDRA CONSTRUCTION DESIGN & BUILD

Walnut, CA

Tundra Construction Design & Build — licensed ADU contractor in Walnut, CA. Detached ADU construction. 7+ years experience.

View Profile 📞 (626) 679 8335

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#9RRSW CONSTRUCTION INC

Walnut, CA

Rrsw Construction Inc — licensed ADU contractor in Walnut, CA. Detached ADU construction. 7+ years experience.

View Profile 📞 (626) 201 2506

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#10SJD&B INC

Walnut, CA

Sjd&B Inc — licensed ADU contractor in Walnut, CA. Detached ADU construction. 10+ years experience.

View Profile 📞 (909) 322 0119

View All 145 Contractors →

💰 How Much Does an ADU Cost in Walnut?

Garage Conversion

$68,500 - $128,500

Converting existing garage to living space

Detached ADU

$147,000 - $322,000

New standalone unit (600-1,200 sqft)

Permit & Fees

$1,097 - $5,097

Plan check, permits, utility connections

* Costs vary based on size, finishes, site conditions, and contractor. Get quotes from multiple Walnut contractors to compare pricing.

❓ Frequently Asked Questions About ADUs in Walnut

How much does it cost to build an ADU in Walnut?▼

The average cost to build an ADU in Walnut ranges from $147,000 to $322,000, or approximately $197 to $372 per square foot. Garage conversions typically cost $68,500 to $128,500.

How long does it take to get an ADU permit in Walnut?▼

The ADU permit process in Walnut typically takes 60 to 120 weeks. California law requires cities to approve or deny ADU permits within 60 days of receiving a complete application.

What are the ADU size limits in Walnut?▼

In Walnut, detached ADUs can be up to 1200 square feet. Attached ADUs are limited to 50% of the primary dwelling or 1,200 sqft, whichever is less. Junior ADUs (JADUs) are limited to 500 sqft and must be within the existing home.

What is the setback requirement for ADUs in Walnut?▼

Walnut requires 4-foot setbacks from side property lines and 4-foot setbacks from rear property lines for new ADU construction. Converted structures (like existing garages) may maintain their current setbacks.

Do I need to provide parking for my ADU in Walnut?▼

No parking is required for ADUs in Walnut if your property is within half a mile of public transit, in a historic district, part of an existing multi-family building, or if the ADU is a garage conversion. Otherwise, one space may be required.

Also See ADU Contractors In

Los Angeles (3215)San Diego (2582)San Francisco (2170)Sacramento (1551)Riverside (925)Fresno (904)Anaheim (784)Irvine (760)

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