37 Tex. Admin. Code § 257.9
Facilities constructed prior to subsequent amendments to these rules, entailing changes, additions, or deletions to the structure of equipment therein, shall not be required to meet the changes unless the change also establishes a date by which the change shall be effected. The facility shall conform to the building, safety, and health requirements of state and local authority. The facility shall also conform to the Texas Accessibility Standards in effect at the time of construction in its entirety regarding the Americans with Disabilities Act Accessibility Guidelines (ADAAG). The commission adopts these rules and 16 TAC §68.20 (relating to Buildings and Facilities Subject to Compliance with the Texas Accessibility Standards) by reference. State standards for a facility which exceed those of the local authority shall take precedence. Where local building codes do not exist, the county shall designate a building code currently in effect; otherwise the International Building Code will apply.
37 Tex. Admin. Code § 257.9