tbh i agree with the residents here. When it inside your own home, you can put whatever you need up to help you out. However, when there are communal areas (ie areas that are "owned" by other people as well as yourself) then they have to agree and if they wont they wont. The person is just a tennant and if living on a first floor is not suitable for them, they could move out, and find smewhere that suits their altered circumstances. If the person who was living there had lost both of their legs in a car accdent, would you MIL insist on fitting a lift? peoples circumstances change. if the person was pregnant with octuplets, would your mum insist on adding an extension to the side of the flats so the family could be accommodated? If the person was in council accommodation for example then they would apply to be moved somewhere more suitable, so this person should find somewhere that fits their circumstances.