TB Construction Helps San Mateo County Homeowners Navigate New 2026 ADU Regulations and Streamlined Permitting Process
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San Carlos-Based General Contractor Reports Surge in Peninsula ADU and Home Addition Projects as New California Laws Eliminate Barriers and Reduce Costs
SAN CARLOS, CA, UNITED STATES, January 21, 2026 /EINPresswire.com/ -- The landscape for accessory dwelling unit (ADU) construction in San Mateo County has shifted dramatically with the arrival of 2026. Three major legislative reforms that took effect January 1 are fundamentally changing how homeowners approach property expansion, offering faster approvals, reduced costs, and clearer standards that experts say represent the most homeowner-friendly ADU environment California has ever created.
The Legislative Changes: What's Different Now
The new regulations address three critical pain points that have historically slowed ADU projects:
Faster Approvals: Local agencies must now determine application completeness within 15 business days and provide ministerial approval within 60 days—a dramatic reduction from the months-long uncertainty that previously characterized the permitting process.
Cost Reductions: ADUs under 750 square feet of interior livable space are now exempt from development impact fees, while units under 500 square feet are exempt from school impact fees. For San Mateo County homeowners, these exemptions can translate to thousands of dollars in savings.
Clearer Standards: New legislation clarifies that ADU size measurements refer to "interior livable space," excluding exterior wall thickness and attic areas with low ceilings. This gives homeowners and designers more usable square footage within the same size limits.
Why Peninsula Homeowners Are Taking Notice
San Mateo County presents a compelling case study for ADU construction. With median home prices in many Peninsula communities exceeding $1.5 million, the economics of building an ADU—typically costing $450-$700 per square foot—suddenly look attractive compared to purchasing additional property.
The rental market reinforces this appeal. Monthly rental rates for ADUs in San Mateo County range from $2,500-$4,500, depending on size and location. Real estate professionals report that homes with legal ADUs command premium prices, with buyers valuing both the income potential and flexible living arrangements.
For many families, the motivations extend beyond financial returns. Homeowners cite the need to house aging parents, create space for adult children, or generate supplemental income as primary drivers for ADU construction.
Local Complexity Remains
While state law establishes minimum standards, San Mateo County municipalities retain significant local control. Zoning regulations, height limits, setback requirements, and design standards vary by city and even by neighborhood.
San Carlos, Redwood City, and Belmont each maintain distinct regulatory frameworks. A setback requirement that applies in one community may differ significantly in another. Height limits vary. Historic district designations add additional layers of review. For homeowners navigating these requirements, understanding local nuances is essential to avoiding costly revisions or project delays.
"The new state legislation has leveled the playing field for homeowners," said Terry Babb, owner of TB Construction Services Corp. "But local requirements still matter tremendously. A well-designed ADU that complies with state law can still face delays or redesigns if it doesn't account for your specific city's zoning and setback rules. That's where local expertise becomes invaluable—understanding these nuances upfront saves time, money, and frustration down the road."
The Construction Economics
Industry data suggests that a 750-square-foot ADU in San Mateo County costs approximately $400,000-$525,000 to construct—a fraction of the cost of purchasing additional property in the region. With rental income potential and property value appreciation, the financial case for ADU construction has strengthened considerably.
What Comes Next
As 2026 unfolds, Peninsula homeowners who have been considering ADU projects face a narrowing window of opportunity. The combination of favorable legislation, strong market fundamentals, and reduced regulatory barriers creates conditions that may not persist indefinitely.
For those ready to move forward, the key to success lies in understanding local requirements, securing experienced contractors familiar with Peninsula-specific regulations, and developing realistic budgets and timelines before breaking ground.
The new regulatory environment has removed many traditional obstacles to ADU construction. What remains is the fundamental challenge of good planning, quality execution, and partnership between homeowners and the professionals they hire to bring their projects to life.
About TB Construction Services Corp
TB Construction Services Corp is a California-licensed general contractor (CA LIC. General B 1072091) based in San Carlos and serving San Mateo County and the broader San Francisco Bay Area. The company works on residential construction projects including ADUs, additions, new construction, and remodels.
Homeowners with questions about ADU feasibility, permitting steps, and city-specific requirements (such as zoning, setbacks, height limits, and inspections) can contact TB Construction Services Corp for additional information about ADU construction in their municipality.
Terry Babb
TB Construction Services Corp
+1 510-825-7062
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