Download 4.1 Main Sources of moisture

Environmental reasons of urban deterioration
Alaa Ibrahim Al Farahaty
Faculty of Engineering, Architecture department
Alexandria University, Alexandria, Egypt.
[email protected]
Abstract: Urban buildings are frequently subject to numerous forms of deteriorations,
regularly in the form of dampness, wall cracks, peeling of finishing , declining of foundations
or even a water penetration to the building . That is beside other factors that could eventually
lead demolishing of the whole structure. Even as some of these factors that cause the building
defect may be instantly noticeable in several cases, in others these factors are not so
understandable. Without doubt, the environmental circumstances are among the main factors of
building deterioration. These circumstances have natural effects without human intervention
and frequently appear over several years depending of the state of the structure. The
environmental causes of deterioration are derived from different shapes .For instance, sun
effects, wind effects and moisture effects. Each effect has specific results and influences on the
building structure elements. Therefore, an accurate cause of a building defect and the form of
its appearance should be understood prior to a sensible remedy can be applied. An exact
identification of a building defect necessitates knowledge and familiarity with the design and
construction of a building combined with an indulgent of methods of scientific exploration.
Keywords: Environmental circumstances, Deterioration causes, Sun effects, wind influences,
moisture consequences.
1- Introduction
Therefore the high temperature causes
deteriorating of the organic materials (eg,
wood, textile, pigments etc) besides
causing fade of colors, brittle surfaces and
peeling of paint from the walls. The level
of the deterioration depends on the material
elasticity, resistance and the amount of the
evaporating internal moisture.
The three main factors of the environmental
circumstances that deteriorate the buildings
structure are the sun effects, moisture effects and
wind effects. Depending of the state of the
building, these factors influences are adequate to
destroy the main elements and materials of any
structure. The paper illustrates the three
deterioration factors and their consequences on
2.2 Thermal expansion:the building's stability and longevity.
The actual temperatures can lead to
2- Sun Effects
either temporary or even permanent changes
2.1 Solar radiation:in physical and chemical properties of the
Band of radiation of Ultra violet and material, Changes of the temperature are
infrared radiation are absorbed by all forms of relevant to assess the consequences of
materials, causing increasing of temperature. thermal expansion and contraction as
Materials are varied at the temperature materials expand during heating and contract
absorption amount depending on the angel of during cooling.
The external wall materials are
the sun ray, wind effect, the thermal expansion
vulnerable
to the sun temperature that leads
and the characteristics of the material. Some
materials surfaces temperature after while of to storing the temperature and transforming
absorbing are greater than the surrounding air it slowly and gradually to the internal
surface.
temperature.
Pambo Fernandez, S.,1999 Factors influencing salt- induced weathering of building sandstone, Phd Diss.The Robert Gardon
University.
Md Azree Othuman Mydin,2012, Hanizam Awang, Factors of Deterioration in Building and the Principles of Repair, ANUL XIX,
NR. 1
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4- Moisture Effects
At the night the external wall is cooled and
loses its stored temperature causing difference
` temperature degree from the internal and
in the
external walls. For the low resistance material,
repeating this process causes deterioration of
the external surfaces features and Imbalance of
the architectural elements. That besides
devastating of the joints of the inner and the
Uncontrolled moisture is the most prevalent
cause of deterioration of structures. It leads
to erosion, corrosion, rot, and ultimately the
destruction of materials, finishes, and
eventually structural components.
The challenge to preservation professionals
is to understand the patterns of moisture
movement in order to better manage it-not
to try to eliminate it as there is never a
single answer to a moisture problem.
Diagnosis and treatment will always differ
depending on where the building is located,
climatic and soil conditions, ground water
effects, and local traditions in building
construction.
3- Wind Effects
The wind properties differ due to the
direction, sources, the passed natural
geographical places and the season in which
the wind blows. The wind degree of velocity is
considered the main source of assessing the
wind limits of benefits and damages. As the
velocity of the wind increases, it has severe
effects on the buildings. Roof coverings (eg.
tiles, slates, lead and copper sheet) can be lifted
in a high wind.
Wind is considered one of the main reasons
of building humidity as the wind carry the rain
water and vapor to the building walls and
materials where deterioration and damage takes
place. The wind carried the vapors in to the
wall of the heritage buildings causing
crystallization of water salts then depositing in
the walls. Therefore on the long term, the walls
plaster and featured deteriorated.
When the wind hits the side of the building
,the exposed side of a building can therefore be
subject to a “pushing” action, while the
protected side can experience a “suction
causing long cracks severe at the exterior
material .One the long term the exterior walls
materials can be deteriorated and lose the
historical features.
Wind causes loading and mechanical
damage to structures. Wind and weather affect
building materials, and after long-term action
the abrasive impact can lead to significant
changes to all exterior parts of the structures
and cause erosion of building material .The
flow around structures has a substantial
influence on the deposition of pollutants,
biological corrosion, cycles of drying and
wetting, as well as mechanical wear of the
exposed surfaces.
4.1 Main Sources of moisture:
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Above grade exterior moisture
Below grade ground moisture
Leaking plumbing pipes and mechanical
Interior moisture
Moisture from maintenance material
4.1.1. Above grade exterior moisture:Due to the buildings age , buildings are
notoriously "drafty," allowing rain and damp
air to enter through deteriorating materials
as a result of deferred maintenance,
structural settlement cracks, or damage from
high winds or storms.
- Most common causes of exterior leaks: Wind driven rain may enter through
deteriorating materials such as brick and
mortar.
 Excessively absorbent materials, such as
soft sandstone, become saturated and can
allow moisture to dampen interior
surfaces.
 Dump air through missing mortar joints;
around cracks in windows, doors, and
wood siding; and into insulated attics.
 Hung gutters or drip edge.
 Improperly installed roofing, or a roofing
type, which is incorrect for the slope of
the roof involved.
Md Azree Othuman Mydin, Hanizam Awang,2012, Factors of Deterioration in Building and the Principles of Repair, ANUL XIX,
NR. 1,
Philip H. Perkins,1976, Concrete Structures: Repair, Waterproofing and Protection, N3
2
4.1.2. Below grade ground moisture
- Most common causes of ground leaks: : Rain water is often referred to as "bulk
```
moisture"
in areas that receive significant
annual rainfalls or infrequent, but heavy,
`
precipitation.
When soil is saturated at the
base of the building, the moisture will wet
footings and crawl spaces or find its way
through cracks in foundation walls and enter
into basements
 Moisture in saturated basement or foundation
walls-also exacerbated by high water tableswill generally rise up within a wall and
eventually cause deterioration of the masonry
and adjacent wooden structural elements
 Builders traditionally left a working area,
known as a builder's trench, around the
exterior of a foundation wall. These trenches
have been known to increase moisture
problems if the infill soil is less than fully
compacted or includes rubble backfill,
which, in some cases, may act as a reservoir
holding damp materials against masonry
walls
 Modern source of ground moisture is a
landscape irrigation system set too close to
the building. Incorrect placement of sprinkler
heads can add a tremendous amount of
moisture at the foundation level and on wall
surfaces
4.1.3. Leaking plumbing pipes and
mechanical:- Most common causes of Leaking plumbing
pipes: Slow leaks at plumbing joints hidden
within walls and ceilings can ultimately rot
floor boards, stain ceiling plaster, and lead
to decay of structural members.
 Central air equipment, have overflow and
condensation pans that require cyclical
maintenance to avoid mold and mildew
growth and corrosion blockage of drainage
channels.
 Broken subsurface pipes or downspout
drainage can leak into the builder's trench
and dampen walls some distance from the
source
 Insulated forced-air sheet metal ductwork
and cold water pipes in walls and ceilings
often allow condensation to form on the
cold metal, which then drips and causes
bubbling plaster and peeling paint.
4.1.4. Interior moisture:- Most common causes of interior
moisture: Moisture can form on single-glazed
windows in winter with exterior
temperatures. Frequent condensation on
interior window surfaces is an indication
that moisture is migrating into exterior
walls, which can cause long-term
damage to historic materials.
 When one area or floor of a building is
air-conditioned and another area is not,
there is the chance for condensation to
occur between the two areas. Most
periodic condensation does not create a
long-term problem.
 Unvented mechanical equipment, such as
gas stoves and driers generate large
quantities of moisture. Moist interior
conditions in hot and humid climates will
generate mold and fungal growth
4.1.5. Moisture from maintenance and
construction materials:- Most common causes: Moisture from maintenance can cause
damage to adjacent historic materials.
Careless use of liquids to wash floors can
lead to water seepage through cracks and
dislodge adhesives and curl materials.
 High-pressure power washing of exterior
walls and roofing materials can force water
into construction joints where it can
dislodge mortar, lift roofing tiles, and
saturate frame walls and masonry.
 Replastered or newly plastered interior
walls or the construction of new additions
attached to historic buildings may hold
moisture for months; new plaster, mortar, or
concrete should be fully cured before they
are painted or finished
Md Azree Othuman Mydin, Hanizam Awang,2012, Factors of Deterioration in Building and the Principles of Repair, ANUL XIX,
NR. 1,
Philip H. Perkins, , 1976., Concrete Structures: Repair, Waterproofing and Protection
3
4.2 Indications and effects of
Moisture:4.2.1 Efflorescence:-
All molds share the characteristic of being
able to grow without sunlight; mold needs only
a nutrient source, moisture, and the right
temperature to proliferate. Mold can eventually
cause structural damage to a wood framed
building, weakening floors and walls.
Efflorescence is the white chalky powder
that you might find on the surface of a
concrete or brick wall. It can be an indication
of moisture intrusion that could lead to major
structural and indoor air quality issues.
Building materials, such as concrete,
wood, brick and stone, are porous materials.
Porous materials can absorb or wick water by
a process called capillary action. The moisture
that creates efflorescence often comes from
groundwater.
-Capillary action:-
4.2.3 Rusts:Rusting is a type of corrosion and it is
caused by the interaction of water and iron or
steel in the presence of oxygen. Rust is a
hydrated iron oxide which although solid in
form is weak and brittle The rust-induced
expansion in strip ties can lead to secondary
damage, such as a redistribution of loads,
buckling and bulging of wall
The rust will have a significantly greater
volume than the original metal. This
expansion of the tie may cause cracking and
distortion of the structure. Cracking will also
reduce the weather resistance of the wall,
which in turn accelerates the rusting process.
The portion of the tie in the outer leaf will
usually be the most severely affected
because of exposure to rain penetration.
However, condensation may also produce
enough moisture to allow rust failure to
occur.
 Salts dissolved by groundwater can be
transported by capillary action through
porous soil. Building materials in contact
with soil will naturally wick the water
inward and upward.
 Concrete footings: they are typically
poured directly onto soil without any
capillary break. Sometimes this is called
rising damp. This is the beginning of how
water can wick upward into a structure
 When the capillary flow of water reaches
the surface of a building material,
evaporation occurs. As the water
evaporates, salt is left behind.
 The potential for damage is increased
because of the repetitive nature of the
mechanical action caused by the cycle of
re-dissolving and re-crystalizing.
The action of water rushing to the surface
due to capillary action creates incredible
forces that can cause materials to crack, flake
and break apart. The pressure from can create
incredibly strong hydrostatic pressure that can
exceed the strength of building materials,
including concrete
4.2.2 Molds:Molds are part of the natural environment.
Molds are fungi that can be found anywhere
inside and outside .When excessive moisture or
water accumulates indoors, mold growth often
will occur, particularly if the moisture problem
remains. While it is impossible to eliminate all
molds and mold spores, controlling moisture
can control indoor mold growth.
Pambo Fernandez, S, 1999, Factors influencing salt- induced weathering of building sandstone, Phd Diss.The Robert Gardon
University.
Md Azree Othuman Mydin, Hanizam Awang, 2012,Factors of Deterioration in Building and the Principles of Repair, ANUL XIX,
NR. 1.
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