Before the Blueprint: How San Diego Homeowners Use Feasibility Studies and Professional Drafting to Plan Their ADU

Accessory dwelling units have become one of the most actively pursued residential projects in San Diego County, driven by California’s ADU-friendly legislation, the region’s persistent housing costs, and homeowners’ interest in rental income, multigenerational living arrangements, and long-term property value. But the path from interest in an ADU to a permitted, built unit is more involved than many homeowners initially expect — involving zoning analysis, site assessment, design development, permit submission, and construction. The homeowners who navigate that path most efficiently are those who engage professional design and drafting services early, understand what their specific property can support before committing to a design direction, and work with someone who knows San Diego’s regulatory environment in detail.

What a Draftsman Brings to an ADU Project in San Diego

A draftsman produces the technical drawings that translate a design concept into a set of documents precise enough for permit submission and construction. In the context of ADU projects, this means floor plans, elevations, sections, site plans, and the supporting details that San Diego’s Development Services Department requires for plan check. Draftsmen who specialize in ADU work in San Diego develop deep familiarity with the city’s and county’s specific submittal requirements, the most common plan check comments, and the design approaches that move through the approval process efficiently.

A draftsman san diego who works regularly on ADU projects understands how San Diego’s setback requirements, height limits, lot coverage rules, and parking exemptions interact for a specific parcel — and produces drawings that reflect those constraints accurately rather than requiring multiple rounds of correction during plan check.

What a San Diego ADU draftsman typically produces:

• Site plan — showing the property boundaries, existing structures, proposed ADU location, setbacks, and access
• Floor plans — dimensioned layouts of the ADU’s interior spaces, showing room sizes, door and window locations, and fixture placement
• Elevations — exterior views of all four sides of the ADU showing height, materials, and architectural features
• Sections — cut-through views showing interior heights, structural elements, and construction assembly
• Foundation and framing details — structural drawings required for permit submission
• Title 24 energy compliance documentation — California’s mandatory energy efficiency calculations
• Supporting details — waterproofing, flashing, stairs, and other construction details required by the plan checker

The distinction between a draftsman and an architect is relevant for homeowners planning an ADU. California law does not require a licensed architect for most residential ADU projects — a qualified draftsman can prepare and stamp the plans for permit submission. For standard ADU designs on straightforward sites, working with a draftsman who specializes in ADUs typically produces faster turnaround, lower design fees, and equivalent permit outcomes compared to engaging an architectural firm that handles many project types.

ADU Plans in San Diego: What the Design Process Involves

San Diego’s ADU regulations have been significantly liberalized under California’s recent ADU laws, which preempt many local restrictions that previously made ADU projects difficult to approve. The city now permits ADUs on most single-family and multi-family residential parcels, has reduced minimum lot size requirements, eliminated most owner-occupancy requirements, and streamlined the permit process for ADUs that meet objective design standards. These changes have made ADU projects more accessible but have not eliminated the need for careful design work — the regulatory environment is more permissive but also more nuanced, with specific rules governing setbacks, heights, and lot coverage that vary by parcel and zone.

Adu plans san diego are developed with an understanding of the specific regulations that apply to the parcel in question — not generic ADU templates applied regardless of site conditions, but designs calibrated to maximize the buildable area and functional program within the constraints the site actually presents.

ADU types and their key design considerations in San Diego:

• Detached ADU — a standalone structure separate from the primary dwelling; subject to setbacks from all property lines, typically four feet from side and rear in most San Diego zones
• Attached ADU — an addition to the primary dwelling sharing at least one wall; subject to the same setback requirements as the primary structure
• Garage conversion ADU — converting an existing attached or detached garage to living space; no additional setbacks required if the existing structure meets current setbacks
• Junior ADU (JADU) — a unit of up to 500 square feet created within the walls of the existing primary dwelling; subject to owner-occupancy requirements and simpler permitting
• Above-garage ADU — a unit constructed above a new or existing garage; subject to height limits that vary by zone

San Diego’s maximum ADU size under state law is 1,200 square feet for detached units, though local regulations may impose lower limits in some zones. Height limits for detached ADUs are typically sixteen feet in most residential zones, with some exceptions for ADUs located within a half-mile of transit. The specific limits that apply to a particular parcel depend on its zoning designation, any applicable overlay zones, and whether the parcel is subject to Coastal Development Permit requirements in San Diego’s coastal zone.

The ADU Feasibility Study: The Right Starting Point

Many homeowners begin the ADU process by contacting a contractor for a construction estimate or by looking at ADU floor plan templates online. Both approaches skip a step that consistently produces better outcomes: a site-specific feasibility study that establishes what the property can actually support before any design work begins or any commitments are made.

An adu feasibility study for a San Diego property analyzes the parcel’s zoning designation, applicable setbacks, lot coverage limits, height restrictions, utility connections, and any site-specific constraints — such as easements, slope conditions, or coastal zone requirements — that affect what can be built and where it can be located on the lot.

What a San Diego ADU Feasibility Study Determines

Questions a feasibility study answers before design begins:

• ADU eligibility — whether the parcel qualifies for an ADU under current state and local regulations
• Buildable area — where on the lot an ADU can be located given setback requirements and existing structures
• Maximum allowable size — the largest ADU the parcel can support given lot coverage limits and zone-specific size caps
• Height allowance — the maximum height permitted for the proposed ADU type in the applicable zone
• Utility feasibility — whether the existing water, sewer, and electrical service can support an additional unit or whether upgrades will be required
• Parking requirements — whether the ADU triggers additional parking under current regulations or qualifies for a parking exemption
• Coastal zone requirements — whether the parcel is subject to Coastal Development Permit requirements that add review time and constraints
• Approximate permit timeline — based on current San Diego Development Services processing times for the applicable ADU type

The feasibility study produces a clear picture of the project’s parameters before any design fees are spent on drawings that may need to be substantially revised when site constraints become apparent. For homeowners who are evaluating whether an ADU project makes financial sense — comparing the estimated construction cost against the rental income potential or the value added to the property — the feasibility study provides the site-specific information needed to make that calculation accurately rather than based on generic assumptions.

From Feasibility to Permitted Plans: The Full Path

Once the feasibility study establishes what the site can support, the design process moves to schematic design — developing the basic layout and program of the ADU within the confirmed constraints — followed by design development and the production of construction documents for permit submission. San Diego’s Development Services Department reviews ADU permit applications for compliance with the California Building Code, Title 24 energy requirements, and applicable zoning standards.

Standard ADU permit processing times in San Diego have varied significantly with application volume, but the city has made efforts to streamline ADU review. Pre-approved ADU plans — standard designs that have already been reviewed for code compliance — can reduce plan check time. A draftsman familiar with San Diego’s submittal requirements produces drawings that minimize plan check comments and corrections, which is one of the most significant factors in the total time between permit submission and permit issuance. For homeowners with a specific timeline — a rental unit needed by a certain date, or a family member’s housing need — that efficiency has direct practical value.