Installation of a residential stair lift is not an issue for most homes. For starters, your staircase has likely bared the load of having large pieces of furniture such as beds or dresses being carried up or down it. The stress and pressure placed upon the stairs by the chair lift is in fact less than that of such furniture.
Another cause of concern that many home owners have is whether their walls would be damaged by the installation and subsequent operation of the system. Since the track is installed directly onto the stairs, and not the walls, any force generated against the walls will be not be sufficient to cause it harm.
A professional installer should be hired for the installation of the wheelchair lift for your home. Proper measurements need to be taken to ensure that no part of the stairs or walls will be damaged during the operation of the stair lift, and more importantly that the user is kept safe.