Why are there often trees placed on top of a building sometime during cunstruction?

Answer 1

The tree is typically plae atop the building once the frame or skeleton has been completed.

History of the "Topping Out" Ceremony

The beam and the tree represent one of the construction industry’s oldest customs – the "topping out" of a completed project. To discover the origin of the topping out, it’s necessary to trace the development of human shelter.

At one time, Europe was covered with a vast forest. Those who inhabited the forest were dependent on trees for their survival. The full, low-hanging boughs provided shelter, the nuts and fruits furnished food, and the fallen dead wood supplied kindling for fires. Because of this great dependence on the forest, people began to revere trees. In fact, trees were the most common deity in Europe prior to the adoption of Christianity.

Scandinavian mythology suggests that humans originated from trees and our souls returned to the trees after death, giving each tree a spirit of its own.

Humans began constructing their shelter with wood. Before cutting a tree, they would formally address the forest, reminding it of the consideration they had always shown toward the trees and asking the forest to grant use of a tree for construction of their home. When the house was complete, the topmost leafy branch of the tree used would be set atop the roof so that the tree spirit would not be rendered homeless. The gesture was supposed to convince the tree spirit of the sincere appreciation of those building the home.

As time passed, the early conception of tree worship gradually changed. The individual tree spirits merged into a single forest god who could pass freely from tree to tree. Trees were no longer placed atop the home to appease spirits, but rather to enlist the blessings of the forest god. The tree branches on top of the home ensured fertility of the land and the home.

The custom of placing a tree on a completed structure came with immigrants to the United States and became an integral part of American culture in barnraisings and housewarmings.

Today thecustom is continued most frequently on completed structures such as bridges and skyscrapers. Ironworkers have carried on the topping out tradition and consider it their own. While others join the celebration of topping out, it is the ironworkers and their skills that make them first to reach the pinnacle of a structure, and it is around this group of workers that topping out revolves.

From The Ironworker, published by the International Association of Bridge, Structural, and Ornamental Ironworkers, Washington, DC.


An addition I found to this:
The custom of placing a pine tree at the top of a new building stems from ancient superstitions. Some cultures feared evil spirits occupied new buildings; some religious groups still practice blessing rites for new homes and buildings today. The first evidence of tree topping occurred in Scandinavia in 700 A.D. and signaled that a completion party was about to begin.
Now, the "topping trees" celebrate the completion of the skeleton of a building; when one is hoisted to the top of a skyscraper, it signals that the building has reached its final height. For some builders the tree may represent that no one on the crew died during construction; it may also represent good luck and future prosperity for the building occupants.

Answer 2

Actually, I wondered that as well myself, and the reasons listed by others may well have some bearing as well, but my brother who is a construction worker told, me many of the guys bring the lunch to work for various reasons, save money, too time consuming to leave and return to have adequate time for a lunch time, the trees offer them a shaded place for their noon day meal and breaks.

Answer 3

because they feel bad about polluting the air with all the machniery and other air polloutants so they figure they'd try to balance it out.

Answer 4

it is to celebrate that the highest point of the building is reached.

Answer 5

it's a tradition by the steelworkers when they have completed the superstructure, why a tree?