Stair lifts are a part of asme 18.1 and have their own specific sets of requirements in the asme "code", and the stair lift asme 12ft maximum will accommodate most situations.
The most difficult part is the 1124A.11 requirement for unassisted entry, operation, and exit. The products need to be carefully specified so all the necessary features and components are included.
If the stair lift will be used in a common use area (such as outside the dwelling unit), then the minimum exit width must be maintained. The minimum width is usually the most difficult situation and precludes stair lifts in most designs due to insufficient space and safe separation from exiting occupants. Negotiation with the Fire Marshal and Building Official is recommended.
thanks very much for the reply - you confirmed what i had thought but it is very helpful to get such confirmation from a trusted source.