Accessory dwelling units, or ADUs, are the small second homes people used to call granny flats: a backyard cottage, a unit over the garage, or a garage converted into living space. Around here they usually come up for one of three reasons. A parent is moving in, an adult kid is moving back, or the owner wants rental income from a lot they already pay for. Whatever the reason, the questions are the same, so here is the honest starting point.

The three flavors

• A detached ADU is a separate small structure in the yard. Most privacy, most construction, most cost.
• An attached ADU shares a wall with the main house, either built on or carved out of existing space.
• A garage conversion turns the structure you already have into living space. The shell exists, which is why this is often the most affordable route — but the shell is also the catch, because older garages were never built to house people. Slabs, framing, and insulation usually need real work.

There is also a junior ADU, a smaller unit of up to 500 square feet created inside the walls of the existing home, usually with its own entrance and a small kitchen.

Why everyone is suddenly building them

For years, local rules made ADUs nearly impossible to approve. California changed that: state law now requires cities to review ADU applications through a streamlined process on a set clock instead of the open-ended hearings that used to kill these projects. Cities still have their own standards on things like height and setbacks, and the details vary from city to city — Dana Point, San Clemente, and Laguna Niguel do not handle everything identically.

The practical takeaway: an ADU that would have been a two-year fight a decade ago is now a normal, approvable project. It still needs plans, permits, and inspections like any other build.

The questions that decide your budget

Before anyone draws a floor plan, these are the answers that move the number most:

• Utilities. Can the unit tie into the existing sewer, water, and electrical, or does the panel need an upgrade and the yard need trenching? This is the most common surprise.
• Access. Is there a reasonable path for construction, or does everything come through a narrow side yard by hand?
• Slope and soil. Flat pads are cheap. Hillsides, common all over south Orange County, are not.
• Who is it for. A rental needs durable finishes and real soundproofing. A unit for a parent may need wider doorways, a zero-step shower, and better lighting — cheap to do on paper, expensive to retrofit later.

We are deliberately not quoting cost ranges here — the four questions above swing the number too much for a generic figure to be honest.

Permits still apply

Everything in our permit guide applies double to ADUs: this is new dwelling space, so it gets plan check, inspections at every stage, and a final sign-off. Unpermitted ADUs are also the single most common unpermitted-work problem we hear about, because an unpermitted rental unit creates insurance and liability exposure most owners never priced in.

How to start

Walk the property with a licensed contractor before you fall in love with a floor plan. A half-hour on site answers the utility, access, and slope questions above and tells you whether your budget and your lot agree with each other. If you are in Dana Point or nearby and an ADU is on your mind, reach out — we will give you a straight answer about whether the project makes sense before you spend money on drawings.