The ADU Boom — Opportunity Meets Complexity
H&M Investment Advisors, Inc. — April 13, 2026
Introduction
Across California, Accessory Dwelling Units (ADUs) are being developed at an accelerated pace—driven by housing demand, rising property values, and the potential for rental income.
While approvals have become more streamlined, the assumption that ADUs are simple projects is often misplaced.
From an expert witness perspective, ADU construction routinely involves the same technical, regulatory, and contractual complexities found in larger developments. When these factors are underestimated, the result is often cost overruns, construction defects, and litigation.
At Potter Expert Witness, these issues are not theoretical—we see them repeatedly in active disputes, where early decisions and incomplete planning ultimately define project outcomes.
Beyond “Four Walls and a Roof”
ADUs are frequently approached as small-scale additions. In practice, they require coordinated execution across multiple disciplines, including:
- Zoning compliance and setbacks
- Structural integration with existing improvements
- Utility capacity and connections
- Fire safety and habitability standards
In construction defect and dispute cases, breakdowns in any of these areas commonly lead to claims involving code violations, deficient work, or scope conflicts.
Design Requirements: Legal Minimums vs. Practical Risk
California regulations do not always require a licensed architect for ADU construction, depending on project scope and classification.
However, meeting minimum regulatory thresholds does not equate to reduced risk.
In our case evaluations, projects that proceed without comprehensive design oversight frequently exhibit:
- Incomplete or unclear design intent
- Inconsistent or non-compliant construction documents
- Increased exposure to change orders and scope disputes
In many instances, the absence of coordinated documentation becomes a central issue in both claims and expert analysis.
Higher-Risk ADU Project Types
Certain ADU configurations consistently present elevated risk:
- Attached ADUs — Improper integration can impact structural performance and create liability exposure
- Detached ADUs — Require full site coordination, grading, and independent systems
- Garage Conversions — Frequently associated with deficiencies in fire safety, insulation, and structural upgrades
These project types are often the subject of disputes when design coordination is incomplete or poorly executed.
Why Design Documentation Matters
From a forensic construction standpoint, the quality of documentation often determines the strength of a claim.
Well-developed plans provide:
- Clear contractor scope
- Alignment with applicable codes
- Consistent bidding conditions
- Defined accountability across project participants
- Stronger support for defensible conclusions in litigation
Conversely, incomplete documentation shifts disputes away from technical facts and toward interpretation—where outcomes become less predictable.
Cost vs. Risk: A Strategic Consideration
Design fees typically represent a relatively small portion of total project cost.
However, attempts to minimize upfront design investment often lead to:
- Rework during construction
- Delays and cost overruns
- Increased likelihood of disputes
In our experience, well-coordinated design documentation functions as a primary risk mitigation tool.
Where Projects Commonly Fail
ADU-related disputes most often stem from:
- Incomplete or uncoordinated plans
- Misalignment between owner expectations and contractor execution
- Failure to meet applicable codes and ordinances
- Unapproved changes during construction
These conditions are significantly less common when projects begin with clear, coordinated documentation.
Final Thoughts
An architect may not be required for every ADU project.
However, from a construction, financial, and legal standpoint, comprehensive design oversight is often a determining factor in project success—and in dispute outcomes when issues arise.
For property owners, the decision is not simply about design. It is about risk.
Need Expert Insight?
Potter Expert Witness provides analysis and testimony in construction-related disputes, including ADU design and development issues.
Our work is grounded in technical clarity, industry standards, and defensible conclusions.