Millbrae ADU Standards
Prefab ADU in Millbrae
What is an Accessory Dwelling Unit (ADU)?
An ADU is an independent residential unit on the same lot as a primary home, providing additional living space, rental opportunities, or multi-generational housing. A prefab ADU is a permanent, factory-built backyard home that meets local zoning and building codes, making it ideal for long-term living.
Tiny homes, often confused with prefab ADUs, are small, mobile units built on wheels. While both can be ADUs, prefab ADUs are stationary and built to last, whereas tiny homes face more zoning challenges due to their mobility.
Planning to Build an ADU in Millbrae?
Millbrae has seen an increase in ADU construction following new regulations. If you’re planning to build an ADU, LiveLarge can guide you through the key development requirements to ensure a smooth process.
Types of ADUs
- Detached: A separate structure built independently from the primary home.
- Attached: A new unit connected to the primary structure.
- Conversion: A repurposed space within an existing home or detached accessory structure.
- Junior ADU (JADU): A conversion of up to 500 square feet within a single-family residence.
Zoning and Lot Size
- ADUs are allowed in areas zoned for single-family or multifamily residential use. JADUs must be within the existing or proposed primary dwelling. ADUs may be:
- Attached to or within a primary dwelling.
- Located within or attached to an accessory structure.
- Detached from the primary dwelling.
- Built within underutilized spaces of multifamily buildings, such as storage rooms or garages.
Size and Floor Area
- Attached ADU: 0-1 Bedroom: Max 850 sq. ft., 2 Bedrooms: Max 1,000 sq. ft., Cannot exceed 50% of the primary residence’s floor area.
- Detached ADU: 0-1 Bedroom: Max 850 sq. ft., 2 Bedrooms: Max 1,000 sq. ft.
- Junior ADU: Max 500 sq. ft.
Setbacks & Height
- Attached ADU: Setbacks: 4-foot side/rear. Height: 16 feet.
- Detached ADU: Setbacks: 4-foot side/rear, 5-foot from the primary home, 20-foot front. Height: 16 feet.
- Conversion ADU: No setbacks required if built within an existing legally permitted structure.
- Junior ADU: Setbacks: 4-foot side/rear. Height: Must match single-family home regulations.
Parking Requirements
- One parking space is required per ADU, in addition to parking for the primary home. However, parking is not required if the ADU:
- Is part of the primary home or an accessory structure.
- It is within ½ mile of public transit.
- Is in an architecturally or historically significant district.
- Is in an area where on-street parking permits are required but not available for ADU residents.
- Is near a designated car-share pickup/drop-off area.
- Replaces a garage, carport, or covered parking structure.
- For more information, contact the Millbrae Planning Division at (650) 259-2341 or VMandapat@ci.millbrae.ca.us.
Why Choose LiveLarge Prefab ADUs?
LiveLarge prefab ADUs are designed to meet Millbrae’s detached ADU regulations, offering a hassle-free way to increase property value. With pre-approved designs and expert guidance, we ensure a smooth approval process.
Let LiveLarge be your trusted partner for your ADU project. Our expertise in design, construction, and permitting will help you maximize your property’s potential. Contact us today to get started!
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