Q. Why do they put pine trees on top of buildings under construction? A. The trees are known as topping trees. They celebrate completion of the skeleton of a building structure. If the building is a skyscraper, the evergreen is attached to the top beam as it is hoisted, a signal that the building has reached its final height. The tree is an ancient construction tradition. There are many such rites associated with a new edifice including the laying of foundation stones, the signing of beams, and ribbon-cuttings. But what’s particularly charming about the construction tree is that it isn’t associated with the beginning or the end of construction. Rather, the tree is associated with the raising of a building’s highest beam or structural element. Hence the name of the rite: the topping-out ceremony. It’s a sign that a construction project has reached its literal apogee, its most auspicious point.
Although the origins of the construction topping out ceremony have become murky through the centuries, it is known that immigrants to the U.S. brought the tradition of the construction Christmas tree with them from Europe and Scandinavia.
The most common reason given for topping out the completed frame is that it originated with the Swedish or Nordic peoples. The custom started when all buildings were made of wood. There was a belief that a spirit lived within each tree. Anyone using that tree for building made their justification for doing so to the forest and then placed a tree on top when the frame was complete to give the tree spirit somewhere to live.