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Attached ADUs in Houston

A self-contained suite built onto your house, with its own entrance, kitchen and bathroom. Good for family who want to be close but not under the same roof line.

Check my lot Design and permits

Small backyard home (ADU): Brown wooden house near green tree

What is an attached ADU?

It is an addition that shares at least one wall with the main house but works as its own home. It has a separate exterior door and does not depend on the main kitchen or bathroom.

How does Houston classify an attached unit?

Carefully. Houston's second-unit allowance in Chapter 42 is described in city materials around a unit above a garage or in a separate structure. A second unit attached to the house may be reviewed differently, for example as a two-unit building, which can change platting and permit questions. As of October 2026, we confirm the classification with the city for your lot before design starts.

Deed restrictions matter here too. Some limit the number of residences or families on a lot regardless of how the unit is attached.

What makes attached ADUs tricky?

Tie-in. The new roof and foundation must meet the existing house cleanly, without trapping water.
Fire separation. Building code requires rated separation between dwelling units that share a wall.
Floodplain. In Houston, an expansion of a third or more of the existing footprint counts as a substantial improvement under the 2018 floodplain rules, which can trigger elevation for the work.
Sound. Insulated, staggered or double walls keep two households from hearing each other.

Is attached cheaper than detached?

It depends on the house. Sharing a wall can shorten utility runs and save some framing. But tying into an older roof or slab, or triggering elevation for an expansion, can erase that saving. We price the attached and detached options side by side where both are allowed.

How much does an attached ADU cost?

As of October 2026, one 2026 Houston market guide estimates about $100,000 to $160,000 for an attached addition. Your written, itemized quote comes after we see the house.

Check what your lot allows

Send your address. We check restrictions, classification and flood rules before we design an addition.