Add to Your Home, Not Just Your Property.
An attached ADU expands your existing house into a complete second living space — its own kitchen, bath, and entrance, sharing one or more walls with your home. ADU Cities designs, permits, and builds attached ADUs across Los Angeles, Orange, Riverside, and San Bernardino counties, all in-house.
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Why Attached Instead of Detached
Lower Cost Than Standalone
Sharing walls, a roofline, and utility connections with your home means less new structure to build. Attached ADUs are the strong middle ground: more private than a garage conversion, more affordable than detached.
Simpler Utility Hookup
Tying into your home’s existing electrical, plumbing, and sewer is simpler and cheaper than running new lines across a yard. That simplicity shows up in both budget and schedule.
Keeps Your Yard Intact
When your lot is modest or you love your backyard, building outward from the house preserves the outdoor space you actually use.
Ideal for Family Living
An attached ADU keeps loved ones close while giving everyone their own front door — aging parents, adult children, or a caregiver get independence with proximity.
How Attached ADUs Work
An attached ADU shares at least one wall with your primary home and functions as a fully independent dwelling: its own entrance, kitchen, and bathroom. From the street, a well-designed attached ADU looks like it was always part of the house.
The connection point is where the engineering matters most. Tying a new structure into an existing home means matching foundations, rooflines, and wall systems so the two behave as one. Our in-house designers and engineers handle the structural tie-in, the city reviews it, and our own licensed crews build it. One team owns the whole thing.
Design Considerations
- Match the existing home. Rooflines, siding, windows, and trim — we design attached ADUs to blend so the finished home reads as one intentional building.
- Plan the entrance thoughtfully. Placement matters for privacy, security, and everyday convenience for both households.
- Think about sound and privacy. We build attached ADUs with proper insulation and wall assemblies between units, so each household keeps its quiet.
- Don’t forget the small separations. Separate metering, independent HVAC controls, and clear boundaries for shared spaces prevent small annoyances — we flag these in design before they become problems.
Common Questions
Straight answers before you even call.
Is an attached ADU cheaper than a detached ADU?
Generally, yes. Sharing walls, roof structure, and utility connections reduces material and labor. Exact savings depend on your home’s layout and the scope of the tie-in — we quote every project individually after a free on-site evaluation.
Can an attached ADU be rented out?
Attached ADUs are legal dwelling units and can be rented long-term in California, subject to your city’s specific rules. We permit every unit through your city so it’s fully legal.
Will construction disrupt my daily life?
Less than you’d expect. Most work happens on the addition itself, and we sequence construction to keep your home livable. You’ll hear it — it’s construction — but you won’t need to move out.
How much does an attached ADU cost?
Our ADU projects typically range from $52,000 to $200,000, with attached ADUs sitting in the middle of that range. Every project begins with a free consultation and an itemized fixed quote. Financing is available, including 0%-interest options for qualified homeowners.
Let’s Talk About What Your Home Could Become.
An attached ADU starts with a conversation about your property and goals. We’ll evaluate your home, explain your options honestly, and give you an itemized fixed quote.