Basement is the floor of a building that lies completely or partially below the ground level. Normally, in residential building, there may be one basement or may not. But there are one or more number of basement floor in commercial types of buildings. Generally, basement is used for car and bike parking, garage or for storage of machinery applicants like generators, electric supply system, water heater, etc. But, in many residential building, basement is also used for living purpose. Wiki
Before talking about the advantage of having basement, it would be better if we know at which case we can or can’t construct basement.
It will not be the better practice to have basement if the water table is high, chance of seepage is high, problem of flooding. The economic analysis should be done between the cost of plot and the advantage of basement. In many place, it become more cheaper to buy more size of plot than constructing basement for same amount of internal space. But it become more economical to have basement in big cities because the cost of plot is high and the space of basement gives high returns of money. It would be always good choice if the depth of foundation is high; having basement not only gives more space but also reduces the cost of foundation.
Advantage of basement:
- More Space
Basement becomes the best option for that area where there is expensive plot. It gives more space making the height of building lesser. Building of lower height are less vulnerable for earthquake and tornado.
- Better site utilization
Due to unavailability of hard strata, deep foundation is needed. If it is necessary to dig deep foundation, it might make economical to add a basement. Then why not to turns this expenses into usable space.
- Use sloping site
If the site is sloppy, it is necessary either to cut or fill for levelling the ground level. Then why not to create semi-basement and get more space to use with less investment.
- Energy efficiency
Since, basement lies under the ground, there is no or fewer directly exposed external wall. So the temperature of room does not overheat or cool down too fast. Due to this reason it helps to retain heat and control fluctuation in temperature. Some basement developer says that a residential building with a basement can be 10-15% more thermally efficient than the house entirely built above ground.
- Multi-purpose use
Basement can be used for different purposes. In residential building, it can be used as living room, play space for children, storage purpose and parking.
Disadvantage of basement:
If the water table is high, then there is high seepage pressure on the basement wall. Not only this, the seepage in the basement made the basement un-usable, this will not worth the investment.
2. Water exit
If the water enter in the basement either due to flood or the seepage, then there will be problem of drainage. Since the ground level is higher, water should be pumped out which increases the expenses of building.
Types of basement of building:
- Daylight or English basement:
It is the type of basement in which half of the floor lies above the ground level and half lies under ground. This types of basement is constructed by raising the level of ground floor. The portion above the ground facilitates for the provision of window for natural day light. But there is no external door for exit. These types of basement provides sound space for living. Also in commercial types of building, it provides easy flow of traffic for parking.
2. Walk-out basement:
Walk-out basement is partial types of basement in which the ground level is sloppy so that one or more sides of basement floor level lies at the ground level where as some are somehow completely under-ground. These basement allows exit door at that side where the level of basement is same as ground level. Some windows also can be fixed depending upon the level of ground.
The underground floor which lies completely below the ground level is called sub-basement. There is no presence of window in this types of basement. There is provision of artificial lighting system. In residential building, these types of basement are normally used for storage purpose.
What are the materials used for construction of basement in building ?
- Poured Concrete:
It is the most common types of construction material for the basement construction. During basement construction, after pouring concrete for building foundation, formwork are set to hold the poured concrete while placed until the poured concrete dry. The basement wall constructed by poured concrete are stronger than other types.
2. Masonry wall:
Brick, stone or concrete block are used to construct wall of basement. Used of masonry makes the construction cheaper and complete in lesser time period. In some place, steel rebar is also used for greater strength and durability.
Pre-cast is the great achievement of modern construction methodology. The pre-cast panel are molded at the industrial site and transported to the building construction site and placed on footers.
Basement Wall of building:
Basement wall are constructed to retain the earth and to prevent moisture from seeping into the building. Since the basement wall is supported by the mat foundation, the steadiness is ensured and therefore the design of the basement wall is restricted to the safe design of vertical stem.
Basement walls are exterior walls constructed at basement level of underground structures (tunnels and other earth sheltered buildings), or retaining walls which must resist lateral earth pressure also as additional pressure due to other type of loading. It carries lateral earth pressure generally as vertical slabs supported by floor framing at the raft foundation and upper floor level. The axial forces within the floor structures are, in turn, either resisted by shear walls or balanced by the lateral earth pressure coming from the other side of the building.
Although basement walls act as vertical slabs supported by the horizontal floor framing , we can’t neglect that during the early construction stage when the upper floor has not yet been built the wall may have to be designed as a cantilever.
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