Disaster resilient housing

Natural disasters are sudden and dangerously powerful, making them a serious threat to communities nationwide. Professionals have learned to anticipate some like hurricanes, blizzards, and tornadoes, but others can still strike with no warning. Earthquakes of any magnitude can occur any time of the year with almost no indications. They can affect small remote areas, or destroy large cities. It’s high time that we think and act upon all serious questions related to climate change, disaster risks and disaster resilient patterns in the field of construction. Housing and settlements are facing greater challenges toughed by changing climate. A disastrously non engineered housing stock threatens to put prosperity out of reach of thousands of people and roll back decades of hard-earned development. The traditional buildings that have incorporated the accumulated traditional wisdom, technology, experience, skill and craft evolved through the ages generally have demonstrated good performance against most natural hazards. However, some modern-day structures, especially the small residential houses, are non-engineered structures without receiving the benefit of such time-tested technology or the input from engineering or architectural professionals. Non-engineered houses can suffer in hazards, but engineered houses can be resilient against hazards. Structures lacking proper connectivity and strength in its components to withstand different types of forces should be avoided when building in areas prone to disasters.

The picture given above shows the weaknesses of a Non – Engineered house. These flaws could be the reasons for the destruction of a house during a disaster. Identifying the weaknesses of the house in which one resides and adopting disaster resilient features while constructing a new house will help in reducing a disaster to their own asset, the house. The weaknesses of a non-engineered house are given below.

Damage assessment criteria

Each category given above represents the percentage of damage caused during a disaster to the building which includes both residential as well as community infrastructure. With the help of such damage assessment criteria, homeowners/anyone can evaluate the destruction caused to their building themselves.

House design followed by hfhi

During the unprecedented flood that happened in Kerala during August 2018, the Disaster Response team of Habitat for Humanity India responded with mainly three interventions which is collectively known as 3R’s and stands for Relief, Rehabilitation and Reconstruction. Reconstruction of houses in North Paravur proved to be a challenge as the house construction in the area followed conventional method irrespective of the soil structure. Some of the major damages identified in the houses were settlement of the foundation and severe cracks in brick walls and floor. The possible reasons behind the above mentioned damages could be design of foundation irrespective of the soil structure and water table, constructing load bearing structures instead framed structures etc.

Habitat India realized the importance of designing the structure of a house which is resilient to a disaster. Rather than creating modifications in the conventional house structure which is a load bearing structure, a framed structure design was developed taking into account the possible disasters that could affect the area in the future. The purpose of creating such a house design is to ensure strength and stability against destruction from flood and other natural disasters.

The design adopted is different from the conventional methods of construction where load bearing structure with DRY rubble masonry as foundation and basement is adopted for every type of soil. This type of foundation is more prone to settlement when constructed in loose soil. In a load bearing structure, the load from the slab is transferred to the ground through brick walls. There are possibilities where a whole house could collapse when the brick walls are damaged.

The HFH house design consists of framed structure where concrete foundations and column – beam structure is provided so that it can take high strength of load of the building. The structural frame consisting of column and beam alone can bear the total load of the building and transfer to the foundation. This design can resist high lateral forces and is more flexible when compared to a load bearing structure. Such Disaster resilient design can be adopted in unreliable soil and also withstand moderate vibrations which ensures safety.

Habitat India has designed three house plans, 500, 430, and, 420 sqft and all the three plans follow the same framed structure design with RCC footings, RCC plinth, RCC column, Brick walls, RCC lintel, RCC support beam and RCC flat roof. A total number of 12 columns are provided in a 500 sqft house plan whereas 9 columns are provided in 430 and 420 sqft plans. The house is designed as per Indian standards, CPWD as well as National Building Codes and the design is verified by Indian Architects Association. For a normal soil type and water table level, the footings goes to a depth of 150cm in to the ground to ensure strength of the foundation and consists of a RCC footing and pedestal column till the ground surface. The depth and the size of the foundation varies according to the type of soil and level of water table in the area. The specification given below for RCC footing might change as it should be designed according to the soil condition of the site.

The RCC specifications of a 430 sqft house design are given below:

Things to consider while constructing disaster resilient houses

Following criteria to be considered while designing & constructing a Disaster Resilient House.