In most jurisdictions throughout the world, property rights are divided into air rights, surface rights, and sub-surface rights. As the name implies, surface rights are rights to use, improve, and sell the surface of the land. Sub-surface rights, on the other hand, are rights that may be reserved when someone sells a property and apply to the right to mine or excavate any minerals found below the surface of the land. Air rights, in most jurisdictions, apply to the air above a property and may also be severed from the surface rights and sold.
The owner of surface rights is free to improve or build anything that the local zoning laws permit on the land. Rights to the surface also generally include the right to plant crops, grass, flowers, or trees. The rights to water found below, or adjacent to, property will vary depending on the jurisdiction, the type of body of water, and whether or not the land is found in an area where water is scare. Often, the government actually owns the rights to water found below the surface.
Most people don't think much about the different rights to land that go along with a piece of property. It pays, however, to carefully read the deed before buying a property, as there was a time when selling a property while reserving the sub-surface rights was not uncommon. This was particularly common in the Old West in the United States during the Gold Rush, or in areas where oil has historically been discovered. When rights to the surface are sold or transferred with a reservation of sub-surface rights, the owner of the sub-surface mineral rights has a right to exercise that right whenever he or she chooses to do so and may use whatever part of the surface is reasonably necessary to extract the minerals.
Air rights are rarely important or relevant to residential property; however, they are often important in large densely-populated urban areas where zoning codes tightly restrict the height of buildings. Technically, a property owner generally owns the right to the air above a property for infinity as long as any structures built on the property do not interfere with air traffic. In reality, most jurisdictions have height restrictions on structures built. An owner may, sometimes, sell his or her air rights that are not being used. For example, in a large city where buildings are restricted to 20 stories, an owner of a property who is not using 15 of his allotted stories may be allowed to sell those air rights, or stories, to another property owner.