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Causes to the Common Custom House Decay |
Fungal Stain / Harmful
Growth
Fungal stain or mould usually
occurs when there is a presence of water or high moisture content
in masonry walls. It can easily flourish in environmental
conditions of high humidity and lack of ventilation. Fungal stain
can be seen on wall surfaces of a bathroom, kitchen, near rainwater
goods including down pipes and gutters; and at washing
areas.
Harmful growth including
creeping and ivy plants can grow on either stone or brick walls.
This happens when dust and dirt penetrate small holes, openings and
cracks in the walls and mortar joints creating a suitable ground
for any seeds to grow. The condition becomes worse when there is
water penetration through the holes. Roots can go deep into the
existing holes causing further cracks and water
penetration.
Erosion of Mortar
Joints
Basically, the main function
of a mortar joint is to even out irregularities of individual
blocks, whether they be of stones or bricks. At the same time it
provides some adhesion between the blocks. Causes to the erosion of
mortar joints include a presence of salt crystallization, scouring
action of winds; and disintegrating effects of plant growing on a
wall or water penetration leading to the concentrations of moisture
and dampness. Decayed mortar can be removed forcibly by the use of
a mechanical disc or carefully raked out by using a knife or spike
manually.
Peeling paint
Peeling paint usually occurs
on building facades, mainly on plastered walls, columns and other
areas which are exposed to excessive rain and dampness. Some
buildings located near the sea may face a much greater risk once
the signs of peeling paint are visible on the exterior walls. This
is because the amount of constant wind, rain and sun received can
easily turn the surfaces of the paint to be chalky and wrinkled or
blistered. In many historic buildings, there are layers of paints
being applied on plastered walls. Apart from lime wash, there are
many types of paints used on wall surfaces including emulsion,
oil-based, tar, bituminous and oil-bound water paint. All of these
require different methods of removing depending on the nature and
conditions of the paints.
Poor Installation of
Air-Conditioning Units
Most of historic buildings in
Malaysia were built without air-conditioning systems. Where
buildings have to contend with high humidity and warm temperatures,
the need to install air-conditioning systems to meet modern
building requirements seems necessary. Window units and openings
are usually closed and sealed to maintain cool air inside the
buildings.
Depending on the building
function, structures and the effects on building fabric; one should
consider four main aspects before deciding to install the
air-conditioning units in any historic buildings. Firstly, the
cooler and drier air produced by the air-conditioning systems may
possibly cause shrinkage of building materials.
Secondly, there will be a
possibility of condensation either on the surfaces or within the
structure of the fabric. This allows the build-up of mould or
fungal stains. Thirdly, there may be problems of installation which
include difficulties in installing the units. Finally, from the
aesthetic point of view, the installations of the air-conditioning
systems in some historic buildings were unfortunately carried out
in a poor manner by simply placing the units on windows, walls or
at the front facade. This affects the appearance of the
buildings.
Defective Plastered
Rendering
In many historic buildings,
defective plastered rendering occurs mostly on external walls,
columns and ceiling. In a humid tropical climate, the defects of
rendering are normally caused by biological attacks arising out of
penetrating rain, evaporation, condensation, air pollution,
dehydration and thermal stress. Other causes may come from mould or
harmful growth, insects, animals and traffic vibration. Prior to
being decomposed and broken apart, plastered rendering may become
cracked due to either shrinkage or movement in the substrate
itself.
Cracking of Walls / Leaning
Walls
Apart from distributing loads
from roofs and floors to foundations, external walls may be harmful
to a building if they are structurally unsound. Cracks in wall,
either vertical or diagonal, are common symptoms of structural
instability. Such defects should be investigated and the cause
diagnosed in either the foundations, weak materials and joints; or
any shrinkage or thermal movements such as timber window frames.
Diagonal cracks, which often being widest at the foundations and
may terminate at the corner of a building, often occur when shallow
foundations are laid on shrinkable sub-soil that is drier than
normal or when there is a physical uplifting action of main roots
of a large tree close to the walls. Furthermore, there are a few
causes to the problem of leaning walls including spreading roof
which forces the weight of a roof down towards the walls, hogging
and sagging due to soil movement, weak foundations due to presence
of dampness, shrinkable clay soil or decayed building materials;
and disturbance of nearby mature trees in which their roots
gradually expand the local settlement.
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Common problems associated with the defective rainwater goods include sagging or missing eaves gutters, corroded or broken galvanized iron down pipes; or leaking rainwater heads. Others may include undersized gutters or down pipes which cause overflow of water, particularly in heavy rain; and an improper disposal of water at ground level. There are a few possible causes to the defective of rainwater goods. Due to inadequate painting, iron rainwater good can become rusted and fractured. Lack of proper fixings of the wall, particularly by means of projecting lead ears or lugs can cause instability to the down pipes. Where the routines of building inspections and maintenance have been neglected, the rainwater goods can be easily exposed to all sorts of defects.
Timber floorboards are widely used in many historic buildings including churches, schools, residential and railway stations. Some of the floorboards are badly abused with serious damages on the surface and deteriorated; leading to further structural problems and unsafety of occupants. The main causes to the deterioration are insect and termite attacks, careless lifting of weakened boards by occupants, electricians or plumbers; lack of natural seasoning and preservatives, and corroded nails.
Timber has been widely used in many historic buildings in Malaysia. It can deteriorate easily if it is exposed to water penetration, high moisture content and loading beyond its capacity. Insect or termite attacks are a common danger to timber. Insect or termite attacks usually happen in a damp and digestible timber which can be found in elements such as wall plates, the feet of rafters and bearing ends of beams and trusses; and in all timbers which are placed against or built into damp walling. It is dangerous to leave the timber with many insect or termite holes because they may soften the timber and form further cracks. Affected timber can be treated by pressure-spraying with insecticide or fumigant insecticidal processes.
10. Roof defects
Besides being one of the main structures in a building, roof may act as a weather shield, giving protection to users or occupants from rain and sun. Therefore, it is important to treat any aging roof tiles. In Malaysia, clay tiles have been widely used in the historic buildings. Common defects of roof tiles include the corrosion of nails fixing the tiles to battens and rafters, the decay of battens; cracking of tiles which may be caused by harmful growth or walk upon. The harmful growth is quite dangerous to the tiles because it may lift the tiles and create leaks. Another aspect to be considered in the common defects is the mortar applied for ridge tiles which tends to decay or flake off over the years.
11. Dampness Penetration Through Walls
Dampness penetration through walls can be a serious matter, particularly to the buildings which are located close to water sources. It can cause not only deterioration to the building structures but damages to furnishings and contents as well. The main cause of dampness is water which may enter a building by a number of different routes.
Water penetration occurs commonly through walls exposed to prevailing wet wind or rain. With the existence of gravity, water is likely to penetrate through capillaries or cracks between mortar joints and bricks or blocks before building up trap moisture behind hard renders and also driving further up the wall to emerge at a higher level.
Dampness may also occur in walls because of other factors such as leaking gutters or down pipes, defective drains, burst plumbing and condensation due to inadequate ventilation. Dampness may also enter a building from the ground through cracks or mortar joints in the foundation walls.
12. Unstable Foundations
Foundations are a part of a building which distributes loads from roofs, walls and floors on to the earth below. They are structurally important to the permanence of a building and if this is lacking there is no point of spending large sums of money on other superficial restoration work. Most of the common problems occured in the foundations depend on the geology of the ground upon which a building stands and is surrounded by, structural failures; and presence and height of a water table. Besides, inherent failures may also happen in a building in which it has to cope and carry any unsettled problems of the foundations.
A famous example is the Leaning Tower of Pisa in Italy of which inherent failures caused by corrections made during construction combined with traffic vibrations, deep construction and abstraction of water from deeper layers of soil have led to its present leaning position. It is important to understand that all of the common problems of the foundations may lead to unstability of the building structures, causing unsafety to users or occupants.
Unstable foundations may occur because of several reasons including shrinking clay soil, resulting when the sub-soil is drying and water table is low which no longer holds the structure above; penetration of dampness and water that may decay walls and foundations; presence of large trees near the building; and the undertaking of extensive excavations or mining nearby. Other cause include landslides caused by heavy rain, heavy construction near an historic building and lowering of water tables, usually by hard landscaping and road areas. Unstable foundations may also occur from traffic vibrations, deteriorating of building materials and the increased loads, particularly when there are changes in building fun
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