In short
Land share is the proportion of the shared plot beneath a building that belongs to an individual unit. It is written on the title deed as a share and must be set in proportion to the unit's size, position and value.
Every unit in a building has a different land share. A larger unit takes a larger share, a smaller one a smaller share. The proportion is not arbitrary: the law requires shares to be proportionate to the value of the units.
Land share is a line most buyers glance past on the deed, yet it becomes decisive in two situations. The first is urban renewal: when a building is demolished and rebuilt, your land share determines your right in the new building. The second is collective decisions: in some resolutions of the owners' assembly, voting weight is calculated by land share.
Why it matters to an investor
A wrongly distributed land share is a defect that goes unnoticed today and creates a serious loss years later. In older buildings and in revenue-sharing transactions in particular, whether the shares were set correctly must always be checked.