We Analyzed 712 Plan Check Comments. Here’s Why Your ADU Permit Keeps Getting Rejected.

We have analyzed multiple plan sets across seven California cities and realized that most permit delays aren’t caused by bad design — they’re caused by missing information. Here’s what we found, and how to fix it before you submit.

What Did We Actually Find When We Dug Into the Data?

We have analyzed multiple plan sets and realized that the same mistakes show up on nearly every project. Not complex engineering failures. Not code misinterpretations. Just missing information.

After years of expediting permits for ADU projects across Menlo Park, San Jose, Los Altos, Los Gatos, Mountain View, Milpitas, and Santa Clara County, we compiled every plan check correction comment we’ve ever received — 712 of them — and ran a full analysis.

The pattern was unmistakable. Plan checkers aren’t rejecting your plans because the design is wrong. They’re sending them back because the designer didn’t show critical information that should have been there from the start.

Think about what that means for your timeline. Every correction cycle adds 2–4 weeks. Two cycles? That’s an extra month or two before you can break ground. And the frustrating part is that almost all of it is preventable.

What Are the Top 5 Mistakes That Delay ADU Permits?

When we sorted all 712 comments by frequency, five problem areas accounted for the vast majority of delays:

1. Incomplete Site Plans (90 corrections — 13% of all comments)

This is the single biggest offender, and it’s where we see the direct impact of rushing past site analysis. Designers routinely skip property line dimensions, setback measurements to structures and eaves, easement locations, building-to-building distances, HVAC placement, utility meter locations, and drainage flow arrows. Every one of these missing items triggers a correction. Miss three or four? That’s an entire review cycle burned on one sheet.

This is exactly why the information you gather upfront matters so much. When you use our free map tools to explore your property before talking to a designer, you’re already collecting the site data that prevents these exact rejections.

2. Electrical Plan Gaps (35 corrections)

Dedicated branch circuits for bathrooms, kitchens, and laundry left off the plans. Tamper-resistant receptacle notes missing. AFCI/GFCI requirements not called out. Surge-protective devices and EV charger provisions forgotten. These are standard California code requirements that belong on every residential plan set — they should be templated, not reinvented each time.

3. Submittal Procedure Failures (34 corrections)

Response letters not included. Changes not clouded and delta’d. Duplicate sheets in the set. Wrong file format. These aren’t technical problems at all — they’re paperwork problems that waste an entire review cycle on zero value.

4. Title 24 / Energy Report Contradictions (27 corrections)

The energy consultant says one thing, the architectural plans show another. Mismatched square footages. Water heater types that don’t agree. IAQ fans required by the energy report but nowhere on the floor plan. Solar PV listed in the Title 24 report but missing from the roof plan. This is a coordination breakdown between two professionals who aren’t cross-checking each other’s work.

5. Fire Separation & Life Safety (24 corrections)

For ADU projects especially, the 1-hour fire-rated wall and floor assemblies between dwelling units are frequently not detailed. Fire-rated door specs, penetration firestop details, tempered glass near doors, and smoke/CO alarm locations get left off the plans. These are life safety items — plan checkers will never let them slide.

Why Does the Initial Information Intake Matter So Much?

Here’s the number that should stop you cold: 53% of all plan check corrections didn’t even cite a specific building code.

That means more than half of all rejections weren’t about code compliance at all. They were about information that was simply missing from the plans. Property line dimensions. Setback measurements. Equipment locations. Drainage direction. Basic site information that should have been collected before the designer ever opened their CAD software.

This is where most ADU projects go sideways — not during design, but before it. If your designer starts drawing without a thorough understanding of your site conditions, setback requirements, easements, utility connections, and local jurisdiction quirks, they’re building on a foundation of guesswork. And the plan checker will catch every gap.

How Does HomeWiP Help You Get It Right the First Time?

This is what we do. We’ve processed permits across seven Bay Area jurisdictions, and we’ve seen every mistake in the book — 712 of them, to be exact.

Our free map tools give you a head start by letting you explore your property’s setbacks and ADU potential before you commit to a design. That initial site analysis is the single most impactful thing you can do to prevent permit delays.

And when you’re ready to move forward, our permit expediting team reviews your plans against the exact checklist we built from this data — 639 items across 17 categories — before they ever reach the plan checker’s desk.

The result? Fewer corrections. Faster approvals. Less money spent waiting.