An attached ADU is a separate dwelling built onto the main house. Because it creates a second unit, it needs the same approval as a detached ADU in Dallas, as of October 2026. If you only need a bedroom suite with no separate kitchen, a standard addition may be simpler to approve.
Is an attached ADU treated differently from a detached one?
Sometimes. Cities can classify two units under one roof differently from a house with a backyard cottage, and suburban codes often write their ADU rules with detached units in mind. We confirm with the city how your design will be reviewed before we finalize it.
What design issues come up?
- Fire separation. Building codes require rated walls and floors between two dwelling units.
- Roof tie-in. Joining a new roof to an older one without creating leaks.
- Foundation movement. A new slab beside an old one has to be designed for clay soils that shift.
- Entrances. Placing the second door so it reads as part of the house, which HOAs often care about.
Suite or second unit: which do I need?
If the person moving in will share meals and the kitchen, a suite addition may be all you need. If they need a full kitchen and real independence, or you may rent it later where that is allowed, plan for an ADU and its approval step.