ADA has its place. It provides guidelines - although many misguided - for mobility assistance. Fortunately, they aren't required to be followed in residential construction of 4 units or less.
Universal design, on the other hand, takes into account mobility and sensory challenges as a matter of course. Additional design considerations can be made, but often, universal design is enough to provide a safe, comfortable, convenient living environment for anyone - people without major challenges and those that do need their homes to be kinder to them.
Essentially universal design meets the needs of the very young to the very old, without regard for their physical size or abilities.
For instruction, more information, or my best selling books on universal design, visit my "aging-in-place" page.