One query that often lands in our inbox is whether one should build a basement for his house or not. Such a query whenever asked is coupled with a request for an urgent reply as the Architect is to be told by the house owner accordingly and further planning and design can be taken up thereafter only. So let’s have a look at various aspects related to basements:
Reasons behind hesitation: The question whether to go for a basement or not, itself holds one’s desire to have a basement yet some unknown fears holding him from saying yes to the Architect. The reasons behind such a hesitation are old beliefs and superstitions. Many people believe that basements are not auspicious for a house and its inhabitants. These beliefs are baseless and should be driven away from one’s mind.
Why such beliefs? In older times, basements were kept dark and dingy. There used to be no proper lighting and ventilation. These were not maintained properly and remained neglected part of the house. Mostly, these were used for dumping old and discarded items. With the passage of time, the family living in the house would avoid going to the basement especially during night and get a spooky feeling on visiting it because of non-maintenance and haphazard dumping of waste items. Such a neglect of basement area led to the beliefs of their being inauspicious and people started avoiding their provision. The word ‘tehkhana’ used for it and their scary presentation in the movies added to the baseless belief.
Say Yes to Basement: A basement can be a boon for a house owner if planned and provided properly and above all, well maintained thereafter. The basement area can be used for multiple purposes. A professional like a Doctor, a lawyer, a CA or a practitioner can make best use of the basement of his house for promoting his profession without disturbing the home and family environment on ground and upper floors. Otherwise, a family can use it for a home theatre, a home gym or as a well-planned storage space.
Technical requirement: If viewed technically, the tilt remains in favour of provision of a basement. Especially if the house plot is low-lying, provision of a basement is the best solution instead of filling up all the low lying area with earth which often doesn’t compact well and leads to settlement of floors. Why to fill the available volumetric space with earth and waste it? Better is to raise the walls and add a basement to the house. Shrinking spaces are another factor. In small sized plots, one can have more livable area on upper floors of the house by creating storage space in the basement.
Essential features of a basement: A basement must have adequate lighting and ventilation. One switch on the side wall of the entrance to the stairs flight leading to basement should switch on all its lights and flood it with light. The ceiling level of basement can be kept higher than courtyard level and all around ventilators, sealed well against entry of water and fitted with exhaust fans can be provided in the vertical space between the courtyard level and basement ceiling level. Otherwise a duct can also be provided to lead light and air to the basement.
Go for RCC Structure: Always choose a RCC structure for the basement. The foundations, the walls, the floor and the roof slab—all should be in RCC. This decision will help in making the basement damp proof, a problem that most house owners fear about basement. Don’t succumb to the practice of raising brick walls with a central reinforced core. For RCC, choose M20 concrete grade or 1 : 1.5 : 3 concrete. The steel reinforcement in footings, walls, floor and roof slab should be designed by a qualified structural engineer, normally attached to the Architect. This is important because the structural engineer will count the earth pressure on the walls of basement while providing steel reinforcement in them.
Add water proofing compound: Choosing RCC instead of brickwork helps in making basement water proof. However, it is always better to add a good water proofing compound to the concrete laid in basement foundation, walls and floor. For every bag of cement to be used while preparing concrete, only about 1 kg of water proofing compound is added. The required quantity of water proofing compound should be procured by estimating total number of cement bags to be consumed. Use a good brand of water proofing compound.
Don’t forget conduits and switches: Wherever RCC is laid in the house, it is very important to embed the electric conduits and switch boxes in it at the designed locations before laying concrete. While in the brick walls, chase is cut after raising the walls and conduits are embedded, in case of concrete, it is not possible to cut RCC. So conduits are laid and boxes are embedded in advance. Any other conduits for dish cable, FTTH or CCTV wires should also be embedded. Vertical conduits to carry split AC copper conduits should also be embedded. In nutshell, as the whole basement structure is in RCC, it is important to embed all conduits, switch boxes, fan hook boxes, light boxes in it.
Well treat the outer face: Always paint the outer surface of RCC walls of the basement with water proofing black epoxy paint before filling earth around basement walls. Avoid painting the walls with bitumen. These water proofing paints for external surfaces of walls are especially prepared for easy working, better water proofing and can be applied even when walls have moisture in them while bitumen has to be applied when walls are completely dry. These paints become rubber-like on drying while bitumen turns hard. Coverage capacity of water proofing paints is good, therefore much quantity is not required.
Basement flooring: For laying basement flooring, the soil should be well compacted and all the grass and weeds should be removed from it. A 4 inch thick layer of fine sand should be laid on it followed by double layer of polythene sheet. Now, the RCC layer should be laid. Steel in RCC can be simply a grid of 8 mm diameter bars in both directions. Thickness of RCC floor should be at least 3 inch with water proofing compound added to the concrete. Next, prefer vitrified tiles over marble in the basement floor to avoid the cumbersome job of grinding and polishing the marble.