Campbell ADU Regulations & Zoning
When do Campbell ADU regulations apply?
Planning an Accessory Dwelling Unit (ADU) starts with knowing what's possible on your property. Here's a quick snapshot of the key build guidelines and permitting details to help you move forward with clarity.
You can build an ADU up to 1,200 square feet with 4-foot setbacks from the side and rear property lines. Campbell allows detached ADUs up to 16 feet in height. Your ADU must maintain a minimum 6-foot separation from other structures on the lot.
Permitting typically takes 2 to 3 months. Campbell is part of the Santa Clara County ADU Program, which provides free resources including pre-approved plans and an ADU cost calculator. The city's central location and VTA light rail access make ADUs attractive for rental income.
What Are the Rules for ADUs in
Campbell
?
Number of ADUs Allowed
Detached ADUs are typically limited to 16 feet in height, with additional height up to 18 feet allowed near transit. Attached ADUs can match the primary dwelling's height up to 25 feet. Conversion ADUs have no height limit since they use existing structures.
Limited two-story configurations may be possible within the 18-foot height limit near transit. Most detached ADUs in Campbell are single-story. Consult with the city planning department for specific guidance on your property.
Detached ADUs require minimum 4-foot setbacks from side and rear property lines, plus at least 6 feet from existing structures. Front setbacks follow the underlying zoning district requirements. Conversions of legally established structures are exempt from setback requirements.
Campbell requires detached ADUs to be at least 6 feet from the primary residence and any other existing structures on the lot for fire safety and maintenance access.
ADU Size Limits
Detached ADUs in Campbell can be up to 1,200 square feet. ADUs up to 800 square feet with 4-foot setbacks and 16-foot height limits qualify for streamlined ministerial approval and cannot be denied due to lot coverage, FAR, or open space requirements.
Attached ADUs are limited to 1,200 square feet or 50% of the primary dwelling's floor area, depending on configuration. State law guarantees attached ADUs of at least 850 square feet for one-bedroom units or 1,000 square feet for two or more bedrooms.
Yes. Under California state law, ADUs up to 800 square feet with 4-foot setbacks and 16-foot height cannot be denied due to lot coverage, FAR, or open space requirements. This is particularly valuable in Campbell where lots may be fully developed.
About MolaADU
This page offers a clear summary of what’s allowed—how many ADUs you can build, size limits, setbacks, and other key requirements. But we go beyond the basics. Our insights are grounded in real-world experience, not just recycled bullet points.
Whether you're planning a rental unit, a guest house, or a space for multigenerational living, we’re here to help you move forward with clarity and confidence.
Height & Setbacks
Detached ADUs are typically limited to 16 feet in height, with additional height up to 18 feet allowed near transit. Attached ADUs can match the primary dwelling's height up to 25 feet. Conversion ADUs have no height limit since they use existing structures.
Limited two-story configurations may be possible within the 18-foot height limit near transit. Most detached ADUs in Campbell are single-story. Consult with the city planning department for specific guidance on your property.
Detached ADUs require minimum 4-foot setbacks from side and rear property lines, plus at least 6 feet from existing structures. Front setbacks follow the underlying zoning district requirements. Conversions of legally established structures are exempt from setback requirements.
Campbell requires detached ADUs to be at least 6 feet from the primary residence and any other existing structures on the lot for fire safety and maintenance access.
Permitting & Timeline
Campbell processes ADU permits within 60 days as required by state law. Overall, expect 2-3 months from complete application to permit issuance. The Santa Clara County ADU Program offers resources and pre-approved plans that can help streamline the process.
Permit costs in Campbell typically range from $5,000 to $15,000 depending on project scope and valuation. No impact fees are charged for ADUs under 750 square feet. The county ADU Program offers a cost calculator to help estimate total project expenses.
Campbell does not routinely require soils reports or building surveys for standard ADU projects. Properties in special zones or with unusual conditions may require additional documentation.
Parking Requirements
No parking is required for ADUs within half a mile of public transit—which covers much of Campbell given VTA light rail and bus service. The Downtown Campbell light rail station and Winchester station provide excellent coverage. Where parking is required, it cannot exceed one space per ADU. Conversion ADUs and JADUs never require parking.
No. When converting a garage or carport to an ADU, replacement parking is not required under California state law. This makes garage conversions a cost-effective option.
If parking is required, it can be located in setback areas, existing driveways (tandem parking), or elsewhere on the property per city standards.
ADU Costs & Rental Income
The total cost to build an ADU in Campbell typically ranges from $250,000 to $450,000 depending on size, design, and site conditions. This includes soft costs (design, permits, engineering) and hard costs (construction, materials, labor). Conversion projects typically cost less, starting around $100,000-$200,000.
Campbell benefits from its central Silicon Valley location, vibrant downtown, and excellent transit. Based on current market data: Bedrooms Average Rent Studio $2,000 - $2,300 1 Bedroom $2,300 - $2,600 2 Bedroom $2,900 - $3,300 3 Bedroom $3,600 - $4,000 Actual rents vary by neighborhood and proximity to downtown or light rail.
Several factors impact your total ADU cost in Campbell: lot conditions, whether you're building detached or converting existing space, the level of finishes, and utility upgrade requirements. Campbell's established neighborhoods may require design sensitivity. Using county pre-approved plans and keeping your ADU under 750 square feet can reduce costs.
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