Waterproofing of External Walls of Buildings

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Waterproofing of External Walls of
Water leakage or more categorically moisture
deterioration of internal finishes (including
mould growth); unsightly damp areas on wall
concentrations of harmful pollutants affecting
occupant's health. The exclusion of moisture
from buildings is therefore not only desirable,
but an utmost concern to the residents of the
Water seepage through external walls in Mumbai
In Mumbai, due to heavy rainfall, water seepage through external walls is
found to be a common defect faced by the house owners. In one of the
surveys conducted on about 10,000 private residential units findings showed
that the use of single layer brick wall was the most common cause of water
seepage through external walls. Almost 90 per cent of the water seepage
occurred through cracks in the plastered brick walls.
In general, water seep through external walls within the first five years of
building completion. The problem is further compounded by Mumbai's high
humidity and abundant rainfall. High wind speeds experienced by high-rise
buildings also increase the likelihood of water seepage. Building envelopes
must, therefore, be adequately designed and constructed to prevent ingress
of water.
General reasons of water seepage through external walls
Joints and cracks in the walls
Absorption and permeation of the materials
Construction joints in the walls
Penetrating dampness
Rising dampness due to capillary action
Poor construction practices
Honeycomb structures in concrete or plaster.

Separation gaps
Significance of external wall coating
Use of either cement or general exterior acrylic paint can not create
impermeable envelope around building. For effective waterproofing of
external walls, the coating material used should function as more protective
than decorative. Products like Dr Fixit Raincoat, an elastomeric exterior
waterproofing coating composed of high quality acrylic emulsion polymer
combined with weather durable pigments, graded fine fillers and additives.
They work as a barrier to liquid water and carbon dioxide gas; but permeable
to water vapor (breathable). The special properties like accommodation of
movement in substrate, bridging existing cracks, maintaining flexibility and
strength over a broad temperature range, resisting dirt pick up and
fungal/algal growth, and over and above, maintaining these properties for
periods of up to 7-10 years, make them very suitable especially for
environment like Mumbai.
Considering the life cycle cost analysis, such acrylic elastomeric wall coating
is a proven approach to long-term protection of exposed building walls as
compared to normal acrylic decorative paints due to its dual properties of
"Waterproofing & Crack Bridging".
Waterproofing Systems & Materials
Water tightness of external walls is usually achieved by providing adequate
wall thickness, proper designing at construction joints and surface rendering
and finishes which serve as barrier against water ingress. But normally no
attention is paid towards critical areas like separation gaps, honeycomb
areas, damp proof courses at plinth level and so on. This results to serious
leakages through external walls and damages to expensive internal paints
and finishing.
A list of various systems used to arrest water penetration in the external
walls for specific reasons is given below:
Sr. No. Reason Waterproofing system/ Materials
1 Cracks in the walls Polymer Modified Mortars / Pastes
2 Joints & Separation gaps Polymer Modified Mortar and sealants
3 Penetrating Dampness Impregnation system
4 Rising Dampness Injection system with siliconate materials

5 Honeycomb structures Flaring mortars / Crystalline system
6 Rain water penetration External Wall Coating
Source: CommonFloor.com
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