Why did so many buildings crumble in Nepal’s recent earthquakes, even those that were built under modern building codes? Lax enforcement fueled by corruption and indifference probably played a part, but so did a lack of public awareness about how to build structures that can sway and shake in an earthquake and absorb some damage without collapsing.
Nepal is not a wealthy country, and its residents must rebuild with whatever materials are available to them — reinforced concrete in the cities, fieldstone and bricks in the countryside. Even so, there are ways to build in an earthquake-prone area that can make homes less likely to fail. For those living in remote, inaccessible regions, however, some of these steps may be impractical.
Here are tips offered by two experts: Maggie Stephenson, who worked for the United Nations on postearthquake reconstruction in Pakistan and Haiti, and Bijay Krishna Upadhyay, community director and training specialist at the National Society for Earthquake Technology-Nepal.
Mr. Upadhyay has been raising awareness about earthquake-resistant construction and training masons in structural integrity. Ms. Stephenson will be advising private and government agencies on rebuilding efforts in Nepal. Their organizations have joined the Shelter Cluster, organized by the Nepali government and the Red Cross to coordinate rebuilding efforts.
“Our people are building their homes themselves,” Mr. Upadhyay said, and those homes can be safe “with each and every material, if done properly.”
1. Build to last.
Ms. Stephenson suggests that whenever possible, people should build permanent homes from the start, rather than improvising temporary shelter and then trying to improve it later. That approach rarely yields structures with integrity, she said.
2. Choose the ground wisely.
Soil conditions under a structure make a big difference in how it fares in an earthquake. Soft or muddy soil amplifies ground movement and makes foundations less stable. Hard or rocky soil is generally better, though in mountainous areas, steeply sloping ground can be prone to slides, and rock outcrops or cliffs uphill from a building site can break loose in a quake.
Mr. Upadhyay offered a simple test for soil integrity: Dig a hole one meter square and one meter deep, and then put the extracted soil back in. If it does not refill the hole to the top or higher, he said, the ground is weak.
3. Plan ahead, and plan conservatively.
Following a prepared plan and a budget will more likely yield a robust structure, with its doors and windows, columns and walls placed sensibly and safely. Making it up along the way — a common practice in rural construction — can lead to unbalanced, incomplete buildings and skimping on materials when money runs out.
Unless a trained engineer is involved, Mr. Upadhyay said, stick to tried-and-true design principles and proportions, and avoid more modern features like a “soft story” — an open ground floor with columns but no walls — because they can make a building vulnerable to collapse. “People have left traditional knowledge and come up with new techniques, but the technology hasn’t been properly implemented,” he said. The National Information Centre for Earthquake Engineering in Kanpur, India, offers more tips and instructions.
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A Nepali girl on a bed frame salvaged from the ruins of her home in the village of Barpak, which lost 90 percent of its homes. CreditDaniel Berehulak for The New York Times
4. Check the quality of materials.
Weak materials will result in a weak construction. Ms. Stephenson suggested several simple field testing methods.
To check the strength of bricks, drop two of them from a height of four feet and see if they crack or break. For steel reinforcing rods, try to bend one of them into a square; if it does not bend three times, it may contain carbon and be too brittle for the purpose.
Timber’s flexibility can be very useful in tying together a masonry structure. But deforestation has made good quality lumber scarce inNepal.
5. Anchor the building well.
The stronger the foundation, the more force a building can generally withstand in an earthquake, provided it is well anchored to the ground. For a single-story masonry house, foundation footings should be at least two and a half to three feet deep and wide, Mr. Upadhyay said.
“It is as if you had a plant that’s not really dug down into the ground,” Ms. Stephenson said. “If it has got shallow roots, you can rip it out easily.”
6. Tie the building together.
Masonry buildings need horizontal bands built into them that can tie the walls together and make the building move as a unit in an earthquake. Steel or reinforced concrete may be used on larger buildings in urban areas, but in a rural house, it is more usually lumber or bamboo.
There should be horizontal bands at the floor level and at the tops and bottoms of windows, and there should be at least one for every two meters of wall height.
The corners of the building should also have vertical reinforcement.
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Thousands of Nepalese villagers are living under makeshift shelters.CreditDaniel Berehulak for The New York Times
7. Columns must be secured.
Mr. Upadhyay said that many buildings collapsed in the capital, Kathmandu, because they were built with columns of varying sizes that were not anchored properly. The columns toppled easily in the quake.
8. Avoid top-heaviness.
Heavy roofs are dangerous in earthquakes. Roofing materials like stone and ceramic tile should be avoided. Corrugated metal, which has become much more common in rural areas, is much lighter and much safer.
9. Keep water away from the foundation.
Standing or flowing water can weaken a masonry building’s foundation and walls, especially when cheap bricks and other materials of uncertain quality have been used. Good drainage is a must to protect the building’s integrity, especially in a country like Nepal that is subject to monsoons.
This article has been originally published in The New York Times on May 14, 2015.
