ADU Construction in Portola Valley

Why Portola Valley is a Strong Market for ADU Construction

Portola Valley homeowners are increasingly building ADUs for extended family, home offices, and rental income. The area’s strong property values and luxury standards make ADU investment a sound decision. Established neighborhoods and proximity to both San Francisco and Silicon Valley create consistent demand for quality construction.

Custom Home builds ADUs in Portola Valley with the same two-phase design-build process we use for custom homes. You see the complete design in 3D and receive itemized pricing before any construction begins.

Types of ADUs We Build in Portola Valley

Detached ADUs

A standalone structure in your backyard, typically 400-1,200 sqft. Detached ADUs offer the most privacy and design flexibility. They work well for rental units, home offices, or multigenerational living. Construction costs in Portola Valley typically range from $375K to $650K.

Attached ADUs

Built as an addition to your existing home, sharing at least one wall. Attached ADUs are typically more cost-effective than detached units since they share structural elements with the main house. They are a good fit for family members who want proximity while maintaining separate living spaces.

Garage Conversions

Converting an existing garage into a living space is the most affordable ADU option in Portola Valley, starting from $200K. Since the structure already exists, you save on foundation, framing, and roofing costs.

Portola Valley ADU Permitting

Portola Valley’s Building Department processes residential permits with oversight from the Architectural and Site Control Commission (ASCC). All new homes and significant additions require ASCC approval, which evaluates site integration, visual impact, and environmental sensitivity. Plan review typically takes 6-10 weeks. Geotechnical and seismic reports are required for most hillside properties.

Custom Home manages the entire ADU permitting process in Portola Valley, preparing plans that meet local requirements for efficient review and approval.

ADU Rental Income Potential in Portola Valley

Portola Valley’s rental market supports strong returns for ADU owners. Estimated monthly rental rates:

• Studio/1-bedroom (400-600 sqft): $2,800-$3,300/month
• 1-bedroom (600-800 sqft): $3,200-$4,200/month
• 2-bedroom (800-1,200 sqft): $4,000-$4,500/month

At these rates, many ADU investments pay for themselves within 7-12 years through rental income alone, not counting the property value increase that a permitted ADU provides.