Can I Build an ADU on My Property? A Qualifier Guide

The short answer

Most single-family lots in Southern California can fit an ADU under state law. Whether yours does — and how big — comes down to four things: setbacks, lot coverage limits, utility access, and site conditions like slope. True disqualifiers are rare; usually these factors shape the unit's size and placement rather than ruling it out. A free feasibility report confirms it for your lot in 48 hours.

The four things that decide it

You don't need a huge yard. You need enough buildable area once the rules are applied. Here's what shapes that:

• Setbacks. How far the unit must sit from property lines. State law caps required side and rear setbacks at four feet for ADUs, which frees up more backyards than people expect.
• Lot coverage. The share of your lot that can be covered by structures. This, plus your existing home's footprint, sets how much room is left.
• Utility access. Distance to sewer, water, and power. Longer runs raise cost but rarely prevent a build.
• Site conditions. Slope, access for equipment, easements, and trees can influence placement and price.

Why a feasibility report beats guessing

Online rules of thumb can't account for your parcel's specific dimensions, easements, and city standards. That's the entire point of a feasibility assessment: it reads your actual lot — zoning, setbacks, coverage, utilities — and returns a written answer on what's possible, plus a preliminary cost range.

It's free, it takes 48 hours, and it commits you to nothing. Most homeowners are surprised by how much their lot supports once the four-foot ADU setback and state size guarantees are applied. If constraints exist, the report tells you honestly and shows what still fits.

Sources

• California HCD — Accessory Dwelling Units
• California HCD — ADU Handbook