Attached ADU vs Detached: Which Is Better?

Attached vs detached ADUs: one shares a wall with the main home, while the other sits separately in the backyard for more privacy

Hey, so you’re at that point where you’re seriously thinking about adding an ADU to your place in Sacramento, maybe for your parents to have their own space but still be right there when you need to check in, or for your adult kids to have privacy without moving out of town, or just to get some rental money coming in and make the house worth more when you eventually sell. The big fork in the road is usually: attached or detached?

I’ve had this conversation with a bunch of people around here, Elk Grove, Roseville, Folsom, Citrus Heights, Rancho Cordova, West Sac, Natomas, Carmichael, Fair Oaks, and out toward Vacaville, Davis, Woodland, Rocklin, Lincoln, Vallejo, Antioch, and there’s no one “right” answer. It really depends on your house, your yard, your budget, and what you’re actually trying to do. But let’s talk through it like we’re just figuring it out together over a coffee, pros, cons, rules, costs, and what I’ve seen actually work best for real families.

Quick Comparison: Attached vs Detached ADU

Here’s the head-to-head in plain English:

• Attached ADU, built onto your main house (shared wall). Feels like a home extension.

• Detached ADU, Standalone unit in the backyard (full separation). Feels like a separate little house.

Quick comparison: attached ADUs feel like a home extension, while detached ADUs feel like a separate small house

Both are ADUs under California law, same basic eligibility, same permit timeline (60 days max), same ownership rules (no owner-occupancy for most new ones in 2026). But the differences matter a lot when you’re deciding what fits your life.

Attached ADU Pros & Cons (Home Extension Style)

Pros I’ve Seen Families Love

• Closer access, super easy to check on aging parents without walking across the yard in the rain or dark.

• Cheaper build, shared wall means less foundation, less roofing, less exterior siding. Usually saves $40k–$80k compared to detached.

• Less yard loss, you don’t eat up as much open space.

• Feels integrated, looks like the house was always meant to have that extra wing.

Cons That Come Up

• Less privacy, sounds carry between the units more than with a detached one.

• Limited size, capped at 50% of the main house area or 1,200 sq ft (whichever is less).

• Design constraints have to match the main house style somewhat.

A couple I know in Roseville went attached because the mom had mobility issues; being able to walk from the kitchen to her unit in seconds was huge. They saved money, too, and now it’s a rental when she’s not there.

Detached ADU Pros & Cons (Standalone Backyard Unit)

Pros That Make People Choose Detached

• Maximum privacy, separate building means quiet, no shared walls, feels like a real second home.

• Bigger size options, up to 1,200 sq ft, even if your main house is small.

• Yard flexibility, place it where it makes sense (corner of yard, behind garage).

• Rental appeal, tenants love the “own little house” vibe.

Cons That Pop Up

• Higher cost, new foundation, full roof, all exterior walls, usually $250k–$400k vs attached’s $200k–$350k.

• More yard space is needed; 4-foot side/rear setbacks eat into usable area on narrow lots.

• Weather exposure, a separate building means more exposure to heat/cold/rain.

A family in Carmichael detached because their adult son wanted total independence; he has his own entrance, own yard area, and they barely hear him. Worth the extra cost for them.

Side-by-Side Comparison Table (Sacramento Rules 2026)

Factor	Attached ADU	Detached ADU
Typical Cost	$200k–$350k	$250k–$400k
Max Size	50% of the main house or 1,200 sq ft	Up to 1,200 sq ft
Height Limit	Up to 25 feet in many zones	16–18 feet in most zones
Setbacks	Follows the main house setbacks	4 feet side/rear minimum
Privacy Level	Moderate (shared wall)	High (separate building)
Yard Impact	Low	Medium–high
Best For	Aging parents, easy access	Adult kids, rentals, max privacy

Your best choice comes down to budget, privacy, and how you plan to use the ADU—family access or long-term rental appeal.

Which One Is Better for You?

There’s no universal “better”; it depends on your situation:

• Pick attached if: you want to keep things close, save money, lose less yard, or have parents/grandparents who need frequent help.

• Pick detached if: privacy is the priority, you have a big enough yard, or you plan to rent it long-term and want it to feel like a separate home.

A family in Fair Oaks attached because their lot was narrow, they got a perfect suite for mom and saved $50k. Another in Elk Grove went detached because they had plenty of yard and wanted the rental to feel like its own place, tenants love it.

For designs that show both styles on real Sacramento lots, check out our ADU models; there are lots of attached and detached examples there.

Get Attached vs Detached Quote

Not sure which is right for your house? Call us at, we’ll look at your lot and tell you what’s realistic for both options, no pressure.

Start My ADU Project

Ready to figure out attached or detached for your family? Let's talk, we’ll help you compare and get a plan going.

Get Attached vs Detached Quote

Want a clear cost comparison for your property? Call us & we’ll give you straight numbers for both attached and detached.

For more on costs (usually attached, cheaper), see our breakdown of how much to build an ADU.

Frequently Asked Questions

1. What’s the main difference between attached and detached ADU?

Attached shares a wall with your main house (home extension); the detached unit is a separate, standalone unit in the yard.

2. Which is cheaper, an attached or detached ADU in Sacramento?

Attached is usually $50k–$100k cheaper due to shared walls and utilities.

3. Which has more privacy, attached or detached?

Detached, with no shared walls, means a quieter and more separate feel.

4. Can attached ADUs be bigger than detached in Sacramento?

No, both max at 1,200 sq ft, but attached is capped at 50% of the main house size if that’s smaller.

5. How do I decide between attached vs detached ADU?

Think access vs privacy, budget vs yard space, and family needs. A local builder can help compare for your lot.