KVPT’s Patan Darbar Earthquake Response Campaign - Work to Date - September 2016

4. Wood Rot and Rising Damp
Description
Many typical Newar structures were either originally
constructed using, or underwent alterations that resulted
in, details that do not properly address issues of protecting
superstructures from rot or rising damp.
Issues
In most traditional Newar structures, the lack of dampproof
course, or vapor barrier, allows moisture to easily
penetrate the lower portions of the building. This is
one of the most problematic issue with these traditional
structures. Due to this issue, the lower sections are deteriorated
and weakened by rot and water damage. Deterioration
of materials from moisture damage can significantly
affect their ability to absorb lateral or seismic
forces, with weakened brick crushing or crumbling and
with weakened wood experiencing shear failure at a very
premature stress level.
In some cases, such as in various pātī structures, there
was originally a void beneath wooden floors to allow
ventilation and to reduce risk of rising damp in interior
walls and columns. In some cases, these details were altered
at some point and the voids were filled in, accelerating
the deterioration of materials.
Options for Seismic Strengthening
To improve protection against water damage in collapsed
structures, a damp proof course can be installed
within the foundations to restrict rising damp from
penetrating up into the structure. This method is variable
in its implementation, and largely based on project-
and site-specific conditions. The foundation conditions
largely dictate where the damp proof course can be
placed. Additional measures should also be taken within
the superstructure, such as copper sheeting to provide a
barrier where timber building elements are located adjacent
to masonry walls. This aids in preventing water
infiltration between building elements.
Top
A typical timber column experiencing
wood rot at its base from a
damp plinth.
Middle
Efflorescence, or salt formation, on
the face of bricks that is caused by
cyclical rising damp that permeates
the porous bricks and evaporates,
leaving any traces of salts and other
minerals on the face of the brick.
This movement of water through
the masonry accelerates deterioration.
The water running up
through the brick breaks down the
brick and erodes the clay mortar.
Bottom
Rotten wood at the plinth level,
around the base of timber columns.
This wood detail was likely implemented
during an intervention.
Improper detailing allowed standing
water to collect and permeate
the wood, resulting in extensive
wood rot.
59