The actual structure that encroaches might be a tree, bush, bay window, stairway, steps, stoop, garage, leaning fence, part of a building, or other fixture.
Some attorneys classify it as a type of easement, related to an easement in gross, while some scholars classify such as one type of encroachment.
[1] When a structural encroachment is created intentionally, it is basically an easement in gross, and may be done by a permit to a government authority.
[2][3] A zoning law may also restrict an intentional structural encroachment.
[4][5][6][7] A structural encroachment may also be created by necessity, by accident, or by prescription.