What are building rights (zachuyot bniya) and why do they matter when buying Israeli property?

Building rights define the maximum built area that can legally be constructed on a given plot under the applicable zoning plan, typically expressed as a plot ratio (the total permitted floor area relative to plot size). When buying an apartment, unused building rights within the building can have real financial value — they may allow a future rooftop apartment, an additional floor, or balcony expansion. For standalone houses, residual building rights may allow a significant addition. Buyers should always have their lawyer or architect verify the building rights position before committing to a purchase.