Why have an oversail licence on a construction project?

Under English law, the freehold owner of land will usually own the air space above their land unless the transfer giving them possession expressly excludes it. A lease does not necessarily carry with it the airspace above a property—it will depend on the drafting of the lease in question. However, it is not always entirely clear whether premises demised include or exclude the airspace (see Can an oversail licence protect a tenant? below).

When a contractor needs to bring a tower crane onto site in order to carry out the works, it needs to consider, during the early stages of the project, whether the jib (the horizontal arm) of its crane will need to swing over, or ‘oversail’, any adjacent land (that does not belong to the developer). If it does, the contractor needs to work out the radius of the jib of the crane and negotiate an oversail licence with each of the adjacent landowners whose land it will swing over.

A crane that oversails adjacent land without an oversail licence