Can I build an ADU on my property? Here's what Reddit actually says
In most of California you can build an ADU on a single-family lot by right — state law bars cities from banning them outright. But whether you actually can, and how big, comes down to your specific address: setbacks, lot conditions, and hazard overlays like hillside, fire, flood, or coastal all change the answer. The common Reddit regret is trusting a contractor's quick yes instead of checking the parcel first.
TL;DR — what people actually say
- State law lets you build an ADU on nearly any single-family or multifamily lot — cities can't ban them outright.
- The real answer is per-address: setbacks, lot size, and hazard overlays (hillside, fire, flood, coastal) change what fits.
- Don't trust a contractor's "sure, you're fine" until you've checked the zoning yourself — the #1 regret in these threads.
- You can confirm most of it for free before you pay anyone for plans.
The by-right basics (California)
Under state ADU law, a detached ADU up to 800 sq ft, 16 ft tall (18 ft near transit), with 4-ft side and rear setbacks generally cannot be denied on a single-family lot (Cal. Gov. Code §66323). That's the floor — your city can allow more, not less. "By right" still means permits, utility hookups, and site-specific rules. It is not "build anything."
How people actually checked their lot
| Route | Pros | Cons |
|---|---|---|
| Call city planning | Authoritative; free | Hold times; you need to know exactly what to ask |
| Hire an architect for a feasibility study | Thorough; pairs with design | $500–$2,000 before you even know if it's a yes |
| Run an instant parcel checker | Free; seconds; reads your actual zoning | Some tools only echo state law — pick one that reads local overlays |
The verdict
Yes, you can almost certainly build an ADU on a standard single-family lot — but confirm the specifics for your address before spending a dollar. If you're in the City of Los Angeles, BackyardCheck reads your parcel's zoning, setbacks, and hazard overlays and gives you a straight answer free, then a $99 report that adds detailed cost and rent ROI. It flags "needs review" instead of faking confidence on unusual lots — exactly the honesty those Reddit threads wish they'd had. It's the cheap first step before plans, not a substitute for a designer or a contractor's bid.
Building an ADU on your property: common questions
In most of California, yes — a detached ADU up to 800 sq ft, 16 ft tall (18 ft near transit), with 4-ft side and rear setbacks generally can't be denied on a single-family lot under Cal. Gov. Code §66323. Your exact size and placement depend on your parcel and any overlays.
Find out what your backyard allows
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