Is an Engineer Stamp Required for My ADU Project in Texas?

Texas has no statewide residential exemption that covers ADUs in the cities that review them — Austin, Dallas, Houston, San Antonio, and Fort Worth all review structural drawings for accessory dwellings. The seal must show the engineer's name, Texas PE number, and date, and the engineer must be in responsible charge of the engineering. Detached ADUs, garage conversions, and attached additions are treated the same at the structural level. Owner-builders don't escape the requirement: the building department asks for the seal regardless of who drafted the plans.

The engineer reviews the floor plan and elevations, designs the foundation for the site's expansive clays — post-tensioned slabs and pier-and-beam are both common in Texas — sizes beams, headers, and the lateral system, and checks wind and uplift design. Garage conversions get extra scrutiny because the existing slab was rarely designed as a dwelling foundation. Utilities and tie-ins are coordinated with the MEP design. Bring the site survey, the geotechnical report, and the architectural plans. Soil data is the item most ADU projects lack.

Use this checklist before engaging an engineer for your ADU: • Engineer of record holds an active Texas PE license, verifiable on the state roster • Dimensioned floor plan and elevations ready for structural review • Site survey showing setbacks, easements, and existing structures • Geotechnical report addressing expansive clay for the specific lot • Foundation designed for soil movement, not just bearing capacity • Garage conversions: existing slab evaluated for dwelling loads • Engineer confirms they'll respond to plan-check corrections on sealed sheets • Seal shows name, Texas PE number, and date on every sealed sheet