An underground parking lot is a large commercial subsoil. These floors are usually created underneath large buildings such as business skyscrapers, hotels, large entertainment centers or malls. The subsoil provides the parking space that an urban building would not be able to provide otherwise. Underground parking lots can be built using two different methods, the top-down process or the bottom-up method. Both have their advantages, but the bottom-up approach tends to be the most cost-effective.
The bottom-up method refers to the order in which the sub floors are constructed. This method makes more sense in the initial exam. The contractors in charge of the project excavate to the deepest level of the underground parking lot, and build that lower level first, along with the main foundations. The other layers are built up, one by one, the contractors put the necessary supports to the next floor while they work. At the end, they reach the ground floor and the construction of the building itself begins.
Concrete is the material of choice for building upside down underground parking lots. Of course, not all concrete is the same, and this concrete has to be especially sturdy to withstand the weight of the construction and the basements themselves. Durable, fine aggregate concrete, mixed with reinforcing chemicals and bonded fibers is often used. However, a number of tricks can provide additional support. Steel bars and large metal columns can provide additional support for large projects that need greater stability.
The bottom-up approach tends to be the most cost-effective for contractors working on the project. It is also the easiest to plan, as the stages of construction progress from the base upwards. Dirt can be quickly transported away from the foundation site prior to commencing work, and errors can be located and ground before floors are built on defective substrates, avoiding the possibility of further damage.
While the bottom-up method can be cheap and fast, it is not always practical. In the downtown areas, building construction often faces very limited space options and a tight deadline. In some cases, it is best for the overall plan to begin building the building itself and build it floor by floor, while digging the basement down one level after another, instead of using the bottom-up approach.