Earthquake-resistant home: How to ensure safety
The recent earthquakes which struck the Nepal- North India belt cannot be erased from our memories because of the extent of damage that it caused. Ever since the disaster, Magicbricks has been receiving a lot of queries on how to ensure whether one’s home is earthquake resistant or whether such a concept is just a myth. We decided to get our users in touch with experts on the subject. The guest speaker was V Suresh, vice chairman, National Building Code of India and former CMD, HUDCO.
Here are the key highlights-
There needs to be prudence in structural design and quality control in construction practices to avoid the nature of such damages as follows-
- Buckling of soft or lower storey columns at the stilts
- Heavy floors, water tanks, pools at intermediate/upper levels. Remember, the slimmer, the better
- Inappropriate design of basements and penthouses
- Incoherent building plan or form without adequate separate sections (example: a lot of projections can create problems)
- Absence of shear walls and bracing
- Failure of stairs due to inadequate flexibility or wrap on effect
- Collateral damage due to collapse of buildings on adjacent structures
- Subsidence of parts due to liquefaction of soil and inadequate foundation design (example: constructions near water bodies)
- Unsafe fixing of roof members (steel of timber) and roof coverings with tiles or sheets
- Inadequate bracing and anchorage between horizontal and vertical members of the roofs, walls and foundations
Building enforcement group is present in every city, for example the municipal corporation.
Sameer Kishore: How can an ordinary person understand about structural safety certificate? What can an individual do?
You either build your own flat on a new plot or you go to the builder. You should consult an engineer who is designing the construction and ask him whether he has taken care of the design with respect to the seismic zone in which your city is. You should rely on the certificate given by him. If you are dealing through a builder, demand to know whether the building plans are approved. Many builders are advertising about seismic safe projects– that is a good marketing information and gives confidence to the buyer.
Rajat Sharma: In small towns where buildings might not be engineered and contractors, builders may give a miss to soil checks, how to convince builders that they need to provide structural certificates?
There may not be many multi–storeyed houses in Tier II and Tier III cities. However, soil checks are important– concerns over liquefaction must be addressed to mitigate disaster. These are fundamental checks, just like a diagnosis by a doctor and cannot be avoided.
IS 4326 gives a large number of construction features which makes building stronger especially in the case of single and double-storeyed houses which are common in the small towns.
Dilip Ellickal: Could you point out some components of retrofitting?
Retrofitting is required when you are already living in a house which is not seismic safe. There are two Indian Standards- IS 13920 and IS 13935. Do refer to these. It gives all the information about seismic strengthening of columns, beams, doors, windows etc. Kindly go through IS 13827, IS 13828 for more information.
Noel Abhishek: What cities fall under Zone 1?
There may be small tremors in Zone 1 but no structural hazards were felt in these cities. However, in the 2015 version of the National Building Code, the cities falling under Seismic Zone 1 are now out of the Indian map effectively. So any zone coming under Zone 2 and below has been clubbed as Zone 2.
The highest disaster prone areas are Himalayan region, Uttarkashi, J&K, North East region, upper portion of Bihar, certain regions of Gujarat, Andaman and Nicobar.