Are there any limitations on the ADA's barrier removal requirements for existing facilities?

Yes. Barrier removal needs to be accomplished only when it is "readily achievable" to do so, which means means "easily accomplishable and able to be carried out without much difficulty or expense."

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

FAQ: When barrier removal is not readily achievable, what kinds of alternative steps are required by the ADA?

FAQ: What are examples of the types of physical modifications or barrier removal that would be readily achievable in most cases?

FAQ: What does the term "readily achievable" mean?

Fact Sheet: Small Business and ADA Readily Achievable Requirements