On June 28, 2013, the Horizontal Property Law (LPH) was amended. It establishes certain conditions (article 10.1.b) for which installing an elevator is mandatory.
If you live in a community of neighbors and the person requesting the installation of an elevator is a person over 70 years old or has a disability, even if they live on the first floor, they are obliged to install an elevator as long as the owners' contribution does not exceed 12 monthly payments of ordinary common expenses.
It could also be mandatory if agreed by the community of owners by simple majority (art. 17.2 LPH).
On the other hand, if part of the space of the dwellings is needed for the installation of the lift, the dwellings must cede it in exchange for compensation, as it is considered a right of way in favour of the community. The compensation will be determined in relation to the value of the square metre and the loss of utility of the local dwelling.