01
The question is concrete
"Can I build an ADU here?" is a geometric question and a regulatory one. Both have answers. Neither requires a 60-page report as the first step.
About
ADUOS exists because homeowners keep getting fooled.
Generic lead-gen sites don’t know your parcel. Over-hopeful builders don’t read setbacks. You end up paying for a $2k study that a good address lookup could’ve answered in a minute.
Why this exists
Three beats behind every ADUOS answer.
02
Uncertainty is honest, not embarrassing
When we don't know something, we label it Needs review. When we do, we link the source. The trust taxonomy sits next to every claim so you never have to guess.
03
The expensive mistake is the wrong direction
Homeowners don't overspend on permits. They overspend on paths that never would have fit — detached when setbacks block it, attached when the foundation can't take it. We want you to pivot early.
Trust taxonomy
Every claim wears a label.
Three states, visible next to every number. You don’t have to guess where a claim came from — it comes with its own receipt.
A primary source says this is true today — official parcel data, municipal code, utility easement records. Links go to the source.
We reasoned this from source-backed facts and conservative assumptions. Shown as a range, not a point. The assumptions are listed alongside.
This depends on evidence we don't have yet — survey data, panel photos, a site visit. We surface it so you know what would change the answer.
San Jose first
One city, one exemplar, one source of truth.
We launched ADUOS in San Jose because the city has clear ADU standards, open parcel data, and a workforce of local builders who’ve already permitted hundreds of them. Every path, every blocker, every cost estimate is calibrated against the specific rules of San Jose — not a national average that means nothing for your lot.
1243 Naglee Ave is the source-backed public case. 1247 Naglee remains a review-pending example so you can see ADUOS refuse to guess when the official address-to-parcel link is unresolved.
Start at your address
The free look is the honest first read.
You decide what to do with it — keep going, save the case, start paid review, or walk away with a clearer read. No pressure, no newsletter pop-up, no builder will cold-call you.