Most ADU plans do not come back because the design is wrong

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There is a particular silence that follows a correction letter. The contractor reads it, the designer reads it, and both privately conclude the other one caused it.

Usually neither did. The design was fine. The set just did not agree with itself.

We keep a written rulebook of the checks we run on a residential permit set before it goes to a city. There are 35 of them. Each one carries a severity, a risk weight and a measured time to fix. When we sort that book by how often the item actually draws a comment, something uncomfortable shows up at the top.

Four of the five highest-risk items are not engineering. They are coordination. The same fact, written two different ways, on two different sheets.

Here are the nine we see most, in that order.

1The set contradicts itself on fuel source

One sheet shows an existing gas meter. Another declares the dwelling all-electric. Both are in the same PDF.

This is the highest-risk item in our book and it is almost never a design decision gone wrong. It is a site plan that inherited a symbol nobody deleted. Mechanical review stops on it. Energy review stops on it. And because the two reviews are usually different people, you can get commented twice for one stray block.

Declare the fuel source once, in one place, and make every other sheet defer to it.

2The load figure does not match the stamped calculation

The electrical sheet prints a service or demand figure. The stamped calculation behind it prints a different one.

Not wildly different. Usually one is an earlier revision that never got chased down after the load calc was redone. We have logged exactly this: a sheet printing 126 A while the governing calculation came out at 152 A.

A reviewer who finds one number disagreeing with its own stamped calc does not just correct that number. They start checking every other number on the set, because you have just told them the numbers are not reliable. That is the real cost.

3The floor area is stated three different ways

Cover sheet says one thing. Site plan says another. The floor plan schedule says a third.

For a JADU this is worse than untidy, because the area is load-bearing in the regulatory sense. It drives the 500 square foot cap. It drives the load calculation. It drives CalGreen thresholds. Three different reviewers are each checking it against a different requirement, and they will each find a different number.

State one total. State the main room separately if you need to. Then use those two numbers everywhere, without exception.

4The same existing room is dimensioned two ways

The bath is one size on the demolition plan and a different size on the proposed plan. Nothing was demolished in that bath.

This happens when the existing conditions get re-measured partway through, or when two people drew the two sheets. It is a direct coordination error and there is nowhere to hide from it, because both sheets are in the same submittal and a reviewer flipping between them will see it in seconds.

One measured dimension set per existing room. Used on both sheets. Identical.

5The open front is declared without its limits

Now we get to real structural work.

A garage conversion almost always has an open front condition, because a garage almost always had a big door in one wall. If the design relies on a cantilevered diaphragm to get around that, the drawings have to state the aspect-ratio limits that make it legal.

Declared without them, this is not a note correction. This is the one that sends the project back for a lateral redesign. It is the most expensive item on this list by a wide margin, and it is specific to exactly the work most Bay Area ADU projects are.

6No abbreviations and symbols legend

A plan checker reads dozens of sets from dozens of offices. Your abbreviations are not their abbreviations.

This one feels trivial and it is not, because of what it does to the rest of the review. A reviewer who cannot decode a callout stops evaluating your design and starts building a list of what they could not read.

7No light and ventilation note

California Residential Code R303. Habitable rooms need natural light and ventilation, or the mechanical equivalent, and the drawings need to say so with the section cited.

This is checked on effectively every residential set in the state. It takes a few minutes to add before submission. Added after, it costs a full round trip.

8No emergency escape and rescue opening note

R310. Same story, same review, usually the same correction letter.

These two travel together so reliably that if a set is missing one it is usually missing both, and if it is missing both it is usually missing the smoke and CO alarm note as well. Small items rarely arrive alone. They arrive as a letter.

9Shear wall capacity printed with no basis

A shear wall schedule that prints a bare capacity in pounds per linear foot, with no stated design basis and no named method.

Here is why a reviewer cares. Seismic and wind do not divide the same way. A tabulated nominal capacity becomes a different allowable number depending on which load case governs and which reduction applies. Print the result without the basis and a reviewer cannot reproduce your number, so they have to ask you to prove it.

The same logic applies to the sill anchorage directly beneath it. Bolt size, spacing, embedment, and the plate washer, which is the part that gets left off. That is where the whole lateral system hands off to the foundation. Left unstated, the inspector cannot pass the pour.

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The pattern worth noticing

Items 1 through 4 are the highest-risk things in our entire rulebook, and not one of them is a question of whether the building works.

They are all the same failure. A fact that exists in more than one place, changed in one place, not chased into the others. It happens on good projects run by competent people, because a permit set is a document with hundreds of facts in it and most of them are written down more than once.

That is also why this class of error survives a careful designer double-checking their own work. You do not catch a disagreement by looking harder at one sheet. You catch it by checking one fact across every sheet that states it, which is a different activity, and a tedious one, and the reason it gets skipped.

The structural items further down the list are real engineering and they need an engineer. But the top of the list is mostly clerical, which is the frustrating part. Those are the cheapest possible errors to prevent and among the most expensive to discover in a correction letter six weeks later.

What to do before your next submittal

Take one fact at a time and follow it across the whole set.

The area. The service size. The fuel source. Each existing room dimension. Then check the notes that get checked every time: R303, R310, R314, R315, R302.6, and whether the energy compliance on the sheets matches the registered document.

Then look at the lateral system and ask whether a stranger could reproduce every number on it from what is printed.

If you would rather see where you stand before doing that, we built a free X-ray that asks twelve questions and scores your set against 26 of these 35 checks. It takes about two minutes and it does not ask for your email before showing you the result.

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TradeStudio, Inc. prepares residential permit sets and structural design for ADU, JADU and garage-conversion projects in Santa Clara and Alameda counties. Drawings and calculations are prepared and stamped under a California Professional Engineer licence.

The rulebook referenced here is the firm's own. The risk weighting on each check is our declared judgement from reviewing sets and reading correction letters. It is not a published municipal statistic and we will not present it as one.