A study by the engineering department of the works and human settlement ministry has found the traditional roofing system to be more susceptible to windstorm damage.
It is the lack of engineered truss system that makes traditional roofing system vulnerable to windstorms, says the study report.
“There is no proper connection to the walls to transfer the loads from roof to the ground,” Gita Maya Sunwar, an engineer with the ministry said.
“There is also a transition in the roofing materials. In the past, they used shingles and now CGI sheets. But they have not changed the truss system. They are using the same truss system. ”
Poor workmanship and techniques, and lack of maintenance were cited as other factors that render traditional roofing system vulnerable.
To improve resilience of traditional roofing system, the department has come up with a Windstorm Resilient Roofing System Guideline.
The guideline lists measures to improve traditional roof truss system to make it resilient while, at the same time, maintaining traditional architectural designs and appearance intact.
It also makes numerous recommendations one of which is to select a site that can shield the house from wind damage. An area behind a mound or a hillock gives the best protection against windstorm.
Securing connections of the truss and using tie down wires to secure roofing are other recommendations.
Windstorm damaged roofs of over 700 houses in 2015 and more than 1,000 houses in April 2011 and December 2013. Majority of the houses that reported damage were rural houses with traditional roofing system.
The Royal Insurance Corporation Limited has paid over Nu 45 m ngultrum in compensation for the damage caused by the windstorms in 2013, 2014 and 2015.
Now that a guideline is in place, rural houses are expected be more resilient to windstorm damage.
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