It's not the violent shaking of the ground itself that
claims the most victims, but the collapse of poorly constructed buildings. The
earthquake sequence destroyed 490,000 houses, mostly traditional mud-brick and
mud-stone houses built and occupied by the rural poor.
" The largest single need identified in the PDNA was for
“housing and human settlements”: 755,000 houses were destroyed or
damaged. "
Central Bureau of Statistics of Nepal for 2014/2015 indicates
40.6% of houses in the country constructed are out of stone and wood. Many
engineers focusing on earthquake safety strive to use local materials, however
the Nepali case appeared bit different, the engineers learn modern construction
materials and try to apply without much innovation on use of local materials,
it was evident from the catalog of house designs distributed by DUDBC
after the 2015 earthquake.
However, we have used the local materials (stone and wood) in
the permanent house reconstruction improving the flaws identified.
Foundation: The foundations of the stone houses were
shallow less than 3 feet depth. The project proposed and adapted foundation at
least of 3 feet depth with bonding to superstructure.
Corner walls: The stones used in corner walls were of
not of regular shape, this was one the reasons of corner walls toppling leading
the toppling of walls and the house. The project focused on strengthening
corner walls by using good stones and tying with wooden vertical posts bonded
with wooden horizontal bands.
Through stone: Through stone placed at the regular
intervals in the walls act as a binder to wall, this was missing in the old
stone houses. Project introduced use of through stones at regular intervals in
the walls of the houses reconstructed.
Lack of bonding: The stone house walls were not bonded with
combination of horizontal and vertical bands. The project introduced wooden
horizontal and vertical bands. Plus, the window and door opening spacing was
adjusted in compliance to the national building codes.
Gabble walls: Gable walls were of stone and not bonded
with the walls and roofs, most of the houses toppled from gable walls. The
project replaced stone gable walls with light material, corrugated galvanized
iron sheet and for some houses wood tied to walls and roofs.
Wood Treatment: In the rural context wood
are painted and some times coated with lube oil ( mobil) to protect them from
termites. Smoky kitchens used to be another protection of wood inside the
house and natural seasoning (use of stack wood) were the practices. Proper
treatment of wood was lacking.
Wood is a natural organic material and as such, can be
degraded by biological organisms: bacteria, fungi (rot) and insects (woodworms
and termites). Wood is also vulnerable to direct sun light and moisture, which
affect its durability and increase the rotting process. Disodium Octaborate
Tetrahydrate (Na2B8O13·4H2O) DOT . Boron-based compounds for wood treatment
were developed in New Zealand and Australia in the 1930s and became
commercialized in 1949. Over nearly 70 years borate mineral has been used
worldwide proving its efficiency as wood treatment.
DOT is a water-soluble solution that can easily penetrate dry
and wet wood. It takes advantage of the moisture content in the wood to
penetrate deeper. For fresh cut timber, where the moisture content can be 35%
or higher by weight, the DOT solution penetrates timber logs more completely
and faster. DOT is known to be an effective, eco-friendly and low-cost remedy
for killing rot organisms and wood-destroying insects in infested wood and
preventing its recurrence.
The project introduced the DOT for the wood treatment in its
housing component. Boric Acid and Borax was prepared at sites of each house
reconstruction following the standard mixes. The woods to be treated are dipped
in the solution for diffusion effect. People used the local wood species
of Chilaune, Salla, Uttis, Lapsi and Sal. One of the advantage of DoT wood
treatment is that even fresh cut woods can be treated with moisture content of
30 to 40 percent and dried wood could be dipped in water for about and
hour before immersing into Borax and Boric solution.
Use of local materials in reconstruction has created
awareness among local people that the salvaged material can be used for
reconstruction, this also reduces financial burden of house owners. (560
Individual Houses are built)
However, 2335 Households surveyed to identify the type of
technical assistance need- in housing revealed the housing interest were of
concrete not of stone and wood.
