The pitch for pre-approved ADU plans in San Diego sounds like a homeowner’s dream: pick a blueprint, skip the expensive architect, save a fortune, and fast-track your build.
But as a San Diego contractor who’s built ADUs ranging from garage conversions to two-story detached units, here’s what we tell every homeowner who asks about pre-approved plans: the savings are real, but they’re smaller than you think — and the tradeoffs are bigger than most people expect.
Before you bank on a “free” permit process, here’s the honest breakdown of where you actually save money — and where you won’t.
The Permit Myth: What Pre-Approved Plans Don’t Change
One of the biggest misconceptions is that a pre-approved plan “erases” the permit process. It doesn’t. In San Diego, even if the building’s structural design is already vetted by the city, these costs and requirements remain:
- Impact Fees: School fees and fire department requirements still apply.
- City Reviews: The city still needs to review how the structure fits on your specific lot and neighborhood.
- Permit Fees: The “plan check” portion may be reduced, but you’re still paying for the permit itself.
As Cliff Kidd, owner of GW Construction, puts it: “The savings are on architects and soft costs — architects and engineers. Not on permits.”
Where the Savings Actually Live: Soft Costs
The primary financial benefit of using pre-approved plans is the reduction in soft costs — specifically, architectural and structural engineering fees.
The Real Math: A realistic ballpark for savings is $10,000 to $20,000 — not the $30K+ that some homeowners expect. If you were planning to pocket $25,000 or more just by choosing a pre-made plan, the numbers won’t add up once you factor in everything else.
You Still Need an Architect (Yes, Really)
Here’s the part that surprises most homeowners: you cannot simply hand a pre-approved blueprint to a contractor and start digging. Every lot in San Diego is different.
“Even if you get the pre-built ones, you still have to draw it on your lot,” Cliff explains. “You still need to hire an architect to put that house on your lot — show your existing plans, show your existing lot, and show how this new building fits. That’s a minimum of $2,500.”
That site-specific work includes:
- Site Plan Creation: Showing exactly where the ADU sits in relation to the main house.
- Utility Mapping: Accounting for sewer lines, water, and electrical hookups.
- Constraint Management: Navigating setbacks, easements, and specific lot slopes.
The Selection Problem: Fewer Options Than You’d Think
San Diego County currently offers roughly six pre-approved ADU plans — and the details are minimal.
“They’re all pretty tiny,” Cliff notes. Most of the available plans are under 1,200 square feet, and the selection doesn’t cover the range of lot types, layouts, or living situations that San Diego homeowners actually need.
If the plan happens to match what you want and fits your lot as-is, you’re in good shape. But if it doesn’t — and it often doesn’t — you’re back to paying for modifications that can erase the savings entirely.
The Biggest Risk: Paying $250K+ for Something You Don’t Actually Want
Pre-approved plans are rigid by definition. When you try to force a one-size-fits-all plan onto a unique lot, you run into real problems:
- The Compromise: You spend $250,000+ on a project but end up with a layout that doesn’t fit your life because it was “convenient.”
- The Change Order Trap: If you decide to move a window or change a wall mid-build, the pre-approved status is often voided — and you’ll pay for new engineering on top of the changes.
- The Long-Term Cost: A plan that doesn’t maximize your lot’s views, sunlight, or privacy can mean lower property value or rental income for years to come.
Cliff’s take is blunt: “You’re going to save 10 grand to get something that you don’t really want. It only makes sense if you actually want it and you’re just using it for a rental.”
Pre-Approved vs. Custom: Which Path Fits Your Project?
The right choice depends on your budget, your lot, and what you’re building the ADU for.
Pre-approved plans work best when:
- You have a simple, flat lot with standard setbacks
- The unit is strictly a rental — “functional” is the priority
- You want the lowest possible entry price on design fees (often $0–$2,500 for the plans + site work)
- You don’t need any layout changes (because any modification can void the pre-approved status)
Custom design is worth the investment when:
- Your lot has a slope, tight access, or unusual dimensions
- You’re building for multi-generational living or plan to live in the unit yourself
- You want to maximize rental income, views, or privacy
- You want to avoid “expensive surprises” during construction because the plan actually accounts for your backyard’s reality
Custom design typically costs $8,000–$15,000+ upfront, but it often pays for itself by preventing costly mid-build changes and maximizing long-term ROI.
The Bottom Line
Pre-approved plans are the “off-the-rack” suit of the construction world. They can work well if your lot is simple, your goals are straightforward, and you’re comfortable with the plan exactly as-is.
Custom designs are the tailored approach. If your San Diego property has a steep grade, an awkward alley entrance, or if you plan on living in the unit yourself, the investment in a custom layout usually pays for itself in livability and long-term value.
At GW Construction, we use a design-build approach — meaning we walk you through every step of the process, from initial lot evaluation to final build, with our team handling design, engineering, and construction under one roof. No getting bounced between architects, engineers, and contractors. One team, one process.
Ready to see what’s possible on your property? If you have questions about your lot, your options, or what an ADU project would actually look like for you, we’re happy to walk you through it.
Reach out to us at 619-848-0738, email hello@constructionsandiego.com, or visit our services page to schedule a free ADU consultation.