How does the ADA affect existing State and local building codes?

Existing codes remain in effect. The ADA allows the Attorney General to certify that a State law, local building code, or similar ordinance that establishes accessibility requirements meets or exceeds the minimum accessibility requirements for public accommodations and commercial facilities. Any State or local government may apply for certification of its code or ordinance. The Attorney General can certify a code or ordinance only after prior notice and a public hearing at which interested people, including individuals with disabilities, are provided an opportunity to testify against the certification.

For additional information, take a look at the following resources:

FAQ: How will a State or local government know that a new building is accessible?

FAQ: What does the ADA require in new construction?