Why an ADU permit clears in six weeks in one California city and takes far longer in another

San Jose stood up that dedicated counter in 2022 and it genuinely did collapse timelines. Six weeks on a custom set is plausible there rather than a fluke. Sacramento is a different animal and the permit runner is right that it does not transfer. For Sacramento the underwriting should not go below nine months, and twelve is more honest, especially if your drawings are custom. What matters before committing a dollar: what is your construction loan rate and does it have an extension option, because that is where the real exposure sits if you blow past your projected certificate of occupancy date.

The permit runner is probably right that it does not transfer. Sacramento was still routing ADU applications through the general building queue as of early 2024, and reported timelines from that period bear it out. A custom plan set on an infill lot in Elk Grove, which is county rather than city though the point holds, went from a February submission to approval the following November. Your six to nine months sounds closer to reality for where you are building. The useful move on the carrying cost math is to build two scenarios and see which one breaks the deal and which one just hurts. If fourteen months breaks it completely then the project probably has a margin problem that a faster permit would not fix anyway. Six weeks is a real number for San Jose right now, and it is a different regulatory universe from Sacramento. Treating it as a benchmark will distort your underwriting.

Sacramento specifically has been running 8 to 12 weeks just for the initial completeness check before they even touch technical review, and that is the part nobody budgets for separately. Your neighbor's six weeks is probably real, but San Jose's counter triages the application the day it comes in, so that dead zone basically disappears. Plan for Sacramento to eat three months before anyone has even read your drawings.

Sacramento has been running around 19 weeks on a pre approved plan, and custom drawings typically add time on top of that.

The six weeks is real but it is not portable, and I think your permit runner already told you why. What I would add is that you should stop treating "permit timeline" as a single number and break it into two separate calls to Sacramento's building department. Ask for the current over-the-counter wait time and then ask separately for the plan check queue. People collapse those together and that is exactly where the surprise comes from. When I was pricing out a garage conversion in Elk Grove last year, the counter said six to eight weeks and technically they were correct, but what they meant was six to eight weeks after plan check cleared, and plan check itself took eleven weeks. So I was looking at close to five months before a shovel touched dirt, and that was a straightforward project with no grading complications.

On your carrying cost buffer, eighteen months is not excessive given where construction loan rates are sitting right now. I have been stress-testing my own numbers at eight percent on the draw and the gap between a six-month permit-to-occupancy window and a fourteen-month one on a $350k build comes out somewhere around $18,000 to $22,000 depending on how your draws are structured. That is a real number that can kill a project that otherwise looked fine on paper. I would also push back gently on the six to nine month estimate you started with. The permit runner may be low. I have been hearing closer to ten to thirteen weeks on plan check alone in parts of Sacramento County right now, before you even get to inspection scheduling. Build your model around the worst credible case and let the project surprise you in the other direction.

Sacramento ran me through two separate permit cycles on the same parcel and the spread between them was wild enough that I stopped trusting any single data point. First one, detached unit, pre-approved stock plan, came back in eleven weeks. Second one, attached conversion, same lot, different inspector assignment apparently, sat for over four months before anyone touched the intake package. Same city, same address, fourteen months apart.

The dedicated counter thing is the whole ballgame and your permit runner is not wrong, but even within jurisdictions that have one, the individual plan checker you land on matters more than people admit. Your neighbor may have also had clean drawings with zero correction cycles, which is a huge variable nobody accounts for when they tell you their timeline. One revision request can add six to eight weeks by itself depending on the queue.

For the carrying cost math I would not plan for six and I would not plan for eighteen. I modeled fourteen on my last one and it came in at twelve, which felt like a win but was mostly luck. If the project only pencils at six months of carry you probably need to look harder at the construction budget or the rent assumption before you touch the permit question at all.