Nepal is a highly earthquake-prone country, where numerous earthquakes occur every year. After 20 years of development of the NNBC, which started in 1994, the number of municipalities implementing the NNBC is only 26 out of 191 (13.61 %) by 2015. In this study data on the destroyed houses of Kathmandu valley has been collated from all the different municipalities concerned and analyzed. After the study, it was found that the buildings of the LSMC and KMC, which adopted the NNBC in 2003 and 2006 respectively, sustained less damage by the earthquake of 25th April, 2015, i.e., 11.07% and 9.45% respectively. The remaining municipalities of the Kathmandu district sustained damage of 41.66% and the remaining area of Lalitpur district outside LSMC had a damage ratio of 40.43%, which is almost four times higher than in KMC and almost four times that of LSMC. However, when the damage data of Bhaktapur was analyzed, it was found that in Bhaktapur municipality, which had just decided to implement the NBC after the earthquake, 45.44% of houses were damaged, whereas the percentage in Bhaktapur district was 40.81%. Similarly, according to the data available by the DEO in Lalitpur district, 516 school buildings out of 1,532 schools, were either damaged or deemed no longer fit for purpose, which is 33.68% of total school blocks. The damage of total RC school blocks was 9.83% (41 out of 417 blocks) and Non-RC was 42.60% (475 out of 1115 blocks). The percent of schools damaged in LSMC was 16.84 % (110 out of 665 blocks) whereas outside LSMC in Lalitpur district, where the NBC has not been implemented, it is 46.83% (406 out of 867 blocks).
The estimated damage by fragility curve, which was developed before 2001, was almost 6 times higher than the actual damage. This also shows the improvement in building conditions in KMC and LSMC. It was concluded that although not all of the buildings had been constructed after the implementation of the NBC, the areas where it has been adopted in KMC and LSMC sustained 4 to 5 times less damage than areas of the Kathmandu valley where it has not been implemented.