1. Construction Practices in Sikkim:
with a special reference to traditional housing
Dinker Gurung, H/449: III Sem, SPA: 2011
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2. Introduction to housing practices in Sikkim:
• The housing practices in Sikkim as like
Photo: A primitive house at Rhenock, Sikkim
any early settlement was determined by
its topography and climatic conditions.
• The traditional housing practices of stone
masonry, wood, bamboo and thatched
roofs were the typical construction.
Photo: A wooden house with ikra house in the
side
Source: Author 2006
• Galvanized Corrugated Roofing was later
introduced for pitched roofs since the
advent of the British in its territories.
• ikra house (Assam type) - a wooden struc-
ture with tin roof, the walls of which are
made of split bamboo plastered with mud
Source: Author 2006 or cement.
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3. Introduction to housing practices in Sikkim:
• Post 1975, after the merger of Sikkim with Photo: A modern house in Rural Sikkim
India as one of its state, the construction
scenario drastically changed
• Reinforced Cement Concrete became the
most widely used construction material
along with the bricks.
Photo: RCC building at Gangtok
Source: Author 2006
• Presently, RCC frame buildings with
masonry in fills are mostly used in private
as well as government constructions.
• There is no formal design practice in
Sikkim even for RCC frame buildings.
Source: Author 2006
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4. Vulnerability of the housing stock
• due to its geographic location and Photo: rural house at Tholung Village
topography is exposed to various natural
hazards like avalanche, landslides and
earthquakes.
• due to its location in Zone IV of the seismic
zonation of India, the entire state is
exposed to the vulnerability to earthquakes
.
Photo: ikra construction in Sikkim
Source: Author 2006
• In addition, the long monsoons period
experienced by Sikkim makes its fragile
slopes exposed to high vulnerability due to
landslides.
• housing stock in Sikkim can be
categorized in to rural, semi-urban and
Source: Author 2005 urban for assessment of its vulnerability to
natural disaster.
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5. Vulnerability of the housing stock in Rural areas
• Due to low height and good horizontal
Photo: ikra house on unstable land
spread, the vulnerability of these
structures to ground shaking is minimum.
• The low self weight of the single storeyed
structure renders it less vulnerable to
damages during earthquakes.
Photo: periphery of Rhenock town, Sikkim
Source: Author 2005
• The random rubble masonry structures in
the higher altitude are more vulnerable to
damages due to earthquake..
• Vulnerability due to mud/land slides in all
Source: Author 2006 areas depends upon the location.
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6. Vulnerability of the housing stock in Semi urban areas
• The semi urban areas are actually villages Photo: housing sin semi urban areas, Sikkim
as defined by the Census but have the
characteristic of the urban areas.
• These settlements are closely packed
houses generally along an important road
and acts as the local commercial centre for
the villages.
Photo: changing typology of construction
Source: Author 2006
• The new typology of construction with poor
construction practices have rendered them
very vulnerable to earthquakes.
• Vulnerability due to mud/land slides in all
Source: Author 2006 areas depends upon the location.
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7. Vulnerability of the housing stock in urban areas
• There are 8 notified urban settlements in Photo: housing sin semi urban areas, Sikkim
Sikkim with a population ranging from
5000 to the largest settlement Gangtok
which has a population of 99,000.
• The housing stock in these areas is mostly
RCC framed G+5 structures or more.
Photo: Gangtok, Sikkim
Source: Author 2005
• The construction of multistoried RCC
frame structures with poor construction
practices have rendered them very
vulnerable to earthquakes.
• Vulnerability due to mud/land slides in all
Source: Author 2005 areas depends upon the location.
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8. Traditional knowledge of housing construction
• Traditional construction consists mostly of Photo: ikra house in Sikkim
typical bamboo houses, known locally as
Ikra, otherwise known as Assam type
housing.
• It is a wooden structure with tin roof, the
walls of which are made of split bamboo
plastered with mud.
Photo: stone masonry house in Sikkim
Source: Author 2006
• Generally, stone masonry structures in the
area are of undressed stones with mud
mortar.
• Earthquake resistant features such as
horizontal bands at various levels and
Source: Subharthi Basu 2011 through stones at corners are not
provided in these constructions.
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9. Influence of new materials & technology on enhancement of
vulnerability of housing stock in Sikkim
Photo: faulty reinforcement
• The introduction of concrete and steel for
the framed structures, ceramic tiles,
marble and kota stone for decorative
purposes, tubular truss for roof support,
aluminium for openings have given rise to
a new typology of construction.
Photo: construction wit modern materials
Source: NICEE@IIT Kanpur
• Generally, stone masonry structures in the
area are of undressed stones with mud
mortar.
• Earthquake resistant features such as
horizontal bands at various levels and
through stones at corners are not
provided in these constructions.
Source: NICEE@IIT Kanpur
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10. Performance of the built environment during the recent earthquake
Photo: failure of RR masonry at basement
• Housing built using traditional knowledge
• Housing built using traditional knowledge
and materials performed well in the recent
earthquake due to its simple configuration
and inherent earthquake resisting
features.
Photo: toppled wooden structure
Source: NICEE@IIT Kanpur
• Only minor damages were reported with no
loss of life due to the failure of traditional
structure reported.
• Instances like toppling of the wooden
house due to lack of foundation was one
Source: www.sikkimexpress.com aspect.
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11. Performance of the built environment during the recent earthquake
• Housing built using modern materials
Photo: damage of building at Gangtok • Performance of the RCC buildings in the
recent earthquake was poor due to poor
design and construction practices.
• Pan caking of the intermediate floors due
to the inability of the columns to take the
load was seen in tall buildings built
beyond the permissible limit of 6 storey’s.
• Failure at beam-column joint due to poor
structural design and workmanship was
seen in large buildings.
• Failure of concrete hollow blocks used as
infill and cladding.
Source: NICEE@IIT Kanpur
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12. Performance of the built environment during the recent earthquake
Photo: State Secretariat building building at Gangtok
Source: NICEE@IIT Kanpur
• Failure of concrete block masonry
cladding at the State Secretariat Building,
Gangtok.
• Failure at beam column joint. Source: NICEE@IIT Kanpur
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13. Performance of the built environment during the recent earthquake
Photo: damaged building at Gangtok Photo: buildings at Gangtok
Source: NICEE@IIT Kanpur Source: NICEE@IIT Kanpur
• Failure of unsupported wall on • Pounding between two buildings
cantilever projection.
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14. Lessons learnt and suggestions for reducing vulnerability of
existing housing stock of the state
• All stakeholders must be educated about • Locally available materials (such as
importance of earthquake-resistant bamboo and other sustainable timber
construction and its role in mitigating alternatives) and traditional technologies
future risk. should be reinstated and integrated with
modern construction practices to have an
• Good concrete and masonry
appropriate design for safe housing.
construction practice and suitable
material should be used for light or
strong partition walls. • Relevant BIS codes and guidelines like
• New building typologies of proven IITK-GSDMA guidelines for seismic
earthquake performance, such as evaluation and strengthening of building is
confined masonry need to be introduced recommended.
for low rise buildings.
• Adhoc retrofitting practices of
questionable performances do not
necessarily make buildings resistant to
future seismic events.
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15. CONCLUSION
• Hazards are here to stay.
• All we have to learn is how to live with it.
• Till the invention of techniques to predict earthquakes,
the only armour we have is preparedness.
THANK YOU
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