Design inspirationAttached ADU
New living space seamlessly bolted to your existing home — shared wall, separate life, one utility bill.
Attached ADU across Greater Los Angeles.
Quick answer: An attached ADU is a separate home with its own entrance, kitchen and bathroom that shares at least one wall with your house. It suits tighter lots and can make utility connections simpler than a detached unit. Its size limit is tied to the size of your main house, so the rules for your lot matter.
An attached ADU shares one wall with your main house. It's the right move when your lot is tight, when you want to keep utilities simple, or when architectural integration matters more than full separation.
Because you're leveraging an existing wall, foundation edge, and often utility runs, attached ADUs typically come in 15–25% below the cost of a comparable detached unit. Size is capped by state rules tied to your main house. Same rentable status. Same address if you want one.
We build across Greater Los Angeles, from Ventura to Long Beach.
Common attached ADU options.
Side attached ADU
Off the side of the house — often replaces an unused side yard with a full 1-bedroom unit.
Rear attached ADU
Extends off the back of the house — preserves the front elevation completely.
Attached studio
Compact 400–500 sq ft unit — cheapest attached configuration.
Attached 1-bedroom
The rental sweet spot — bedroom, full bath, kitchen, living.
Attached 2-bedroom
For multi-generational family or premium long-term rental.
Attached + interior connection
Locking interior door between main house and ADU — flexible for aging parents or teen suite.
What's included in every HomeAdd project.
Every phase, in order.
- 1Feasibility & design
Site walk, zoning check, design.
- 2Construction docs
Engineering, Title 24, MEP, permit set.
- 3Plan check & permits
California's 60-day ADU review clock, corrections, permit.
- 4Site prep & foundation
Foundation, footings tied to existing structure.
- 5Framing & envelope
Framing, roofing, windows, matched exterior.
- 6MEP & insulation
Rough electrical, plumbing, HVAC, insulation.
- 7Kitchen, bath, finishes
Cabinetry, tile, flooring, paint, fixtures.
- 8Final inspection & handoff
Building final, address (if separate), punch list, warranty.
Planning ranges (Los Angeles & Ventura)
Preliminary planning ranges vary by jurisdiction, site conditions, design, utilities, and finish level. A written proposal follows feasibility and design.
One-room unit with full kitchen and bath.
Separated bedroom, full bath, kitchen, living.
Larger family-scale ADU with premium finishes.
Filed, corrected, inspected — by us.
We prepare and submit the permit package to the department that reviews your address, whether that is LADBS, LA County, Ventura County, or a city building department in Los Angeles or Ventura County. You never touch a portal, sit on hold, or drive to a counter.
- ADU permit (California's 60-day review timeline)
- Structural plan check
- Title 24 energy compliance
- MEP permits
- Utility separation (as needed)
- Fire separation between units
- Address assignment (as configured)
- Final building inspection & CofO
What this scope typically looks like.
Representative planning images of the kind of build described above.
Questions homeowners ask first.
Still have questions? Call (877) 544-1543 or request a callback — a HomeAdd project advisor will walk your address on Google Earth with you on the phone.
Attached vs detached — which should I build?+
Attached ADUs can cost less because they share a wall, foundation edge and utilities with the house, but the difference depends on the design and site. Detached ADUs offer more separation. If your lot supports either, we walk you through the tradeoffs in feasibility.
Do we need a fire wall between the ADU and main house?+
Building codes require fire-rated separation where the two units meet; the plans specify the exact assembly for your project.
Can utilities be shared?+
Yes for most systems. Some cities require separate water sub-meters for ADUs. We confirm your city's rule and design accordingly.
Can I add an interior door between the two?+
Absolutely. A locking interior connection is popular for aging-in-place, teen suites, and hybrid live-work setups. Doesn't affect the ADU's rentable status when locked.
Does an attached ADU affect my property tax?+
New square footage is generally assessed for the value it adds, not the whole house; confirm the details with your County Assessor.
How much rent for an attached ADU?+
Rent depends on size, location, layout and condition. Check current local listings or a property manager for comparable units in your neighborhood.
Other ADU options for your lot.
Ready to plan your attached ADU?
We'll walk your property, pull the zoning, and give you a real budget and timeline — before you spend a dollar on design.