Insects could be defined as ancient race of animals which have been in existence for millions of years. They are capable of survival under most adverse conditions and environments. Man is affected in a multiplicity of ways by insects. Insects can attack his body, his food, crops, fruits, other agricultural products including his stored possessions and even the house in which he lives.
The type of insects known as termites cause maximum damage to the
buildings. Termites are divided mainly into following two types:
1.Dry wood termites
2. Subterranean termites
Dry wood termites:
Dry wood termites live in wood and do not maintain contact with the
ground. They normally build nests within the dry timber members like door
window frames, wooden furniture etc. and destroy them gradually. They are
however, not as common as subterranean termites and they cause lesser damage to
the buildings.
Subterranean termites:
On the other hand are mainly responsible for causing damage to the
buildings and its contents. Unlike dry wood termites they live in soil and
require moisture for their existence. They build underground nests or colonies
and form mud wall tunnels or runways which serve as protected shelter for their
movements. Sometimes the build nests near ground in stumps of dead trees or
create colonies in the form of dome shaped mounds on the ground. It is through
these mud wall tubes that they maintain direct contact with the soil for
meeting their moisture requirements and conditions of darkness essentially
needed for their survival. The termites enter the building through foundations
or from ground adjacent to buildings and advance upward through floors
destroying everything that comes within this reach. They may also enter the
building through cracks and cervices in masonry and joints or cracks in floors
in contact with ground. Termites eat cellulosic materials like wood, grass,
etc. and also attack materials like leather, plastics, rubber, furniture,
furnishings; clothings, stationary etc.
In the absence of adequate data, it is rather difficult to estimate the
exact loss due to termite attack. The total figure could, however be assumed to
run into several millions of rupees every year.
In situations, where the termites have already attacked a building,
suitable treatment should be given to ensure their extermination and to protect
the building and its contents from further damage.
TYPES OF ANTI-TERMITE TREATMENT
The anti-termite treatment in buildings may be broadly divided into two
categories:
1.Pre-construction treatment
2. Post construction treatment
PRE CONSTRUCTION TREATMENT
This treatment is carried out right from the stage of initiating the
construction activities for the building. The various operations involved in
this treatment could be summarised as under:
1.Site Preparation
This consists in removing stumps, roots, logs, waste wood etc. from the
site where the building is to be constructed. In case the termites mound are
discovered within the plinth area of the building they should be destroyed by
use of insecticide solution. For this treatment, holes should be made into the
mound at several places by use of crow bar and the insecticides taken in the
form of water suspension or emulsion should be poured into the holes. The
quantity of insecticide solution to be used will depend of the size of mound.
2. Soil Treatment
This operation consists in poisoning the soil underneath the building and
around the foundations of the buildings with insecticide solution consisting of
any one of the following chemicals in water emulsion.
Aldrin 0.5%
Heptachlor 0.5%
Chlordane 1%
In order that, the soil treatment may be fully effective, the chemical
water emulsion should be applied in required dosage on entire area of ground
covered by the building. The soil treatment should be applied in the following
stages:
· The bottom surface and the sides of
the foundation trenches, column pits and basements should be treated by
applying chemical water emulsion at the rate of 5 litre per sq.m. of the
surface area.
· After the foundation for the walls,
columns, piers and retaining walls of the basement come up, treat the back fill
earth in immediate contact with each side of the foundation with the chemical
emulsion @ 7.5 litres per sq.m. of the vertical surface of the foundation
masonry.
In cases of R.C.C. columns or R.C.C. basement walls, there is no
possibility of voids which can permit entry of termites and hence it is not
necessary to start anti termite treatment right from the bottom of excavation.
In such cases, the treatment should start at depth of 500 mm. below ground
level. Thus the back fill around R.C.C. columns, beams and entire basements
walls from a depth of 500 mm. upto ground level only should be treated with
chemical emulsion @ 7.5 litres per sq.m. of vertical surface.
Treatment of top surface of plinth
filling:
Prior of laying the sand bed or subgrade for the ground floor of the
building, top surface of the consolidated earth filling within the plinth walls
should be levelled and treated with chemical emulsion to 5 litres sq.m. of the
surface. If the consolidated earth fill does not allow the chemical emulsion to
seep through, 50 to 75 mm deep holes are made at 150 mm centres both ways with
crow bars on the earth surface to permit easy seepage and to achieve uniform
absorption of the chemical emulsion by the earth fill.
Treatment of junctions of the wall
and floor:
The junctions of walls and the floors require special attention to ensure
effective soil treatment. For this it is important to establish vertical
continuity of the poisoned soil barrier on thinner wall surface upto top of
consolidated earth filling in plinth. This is achieved by making 30 mm. wide
and 30 mm. deep channels at the junction of walls and columns with the earth
filling in the plinth. Holes are thereafter made in the channel at 150 mm.
apart up to ground level with crow bar and then chemical emulsion is poured in
the channel @ 7.5 litres per sq.m. of the vertical wall or column surface.
After the treatment, the earth should be immediately tamped back into the holes
and channel.
Treatment of soil along external
periphery of building:
Despite the treatments given above termites are liable to gain excess in
the building from the ground surface around the external periphery of the
building. In order to check this, 300 mm. deep holes at 150 mm. centre are dug
all along the external perimeter of the building and filled with chemical
emulsion @ 2.25 litres per linear metre. After the treatment the earth should
be tamped back in the holes. In case the building is to have apron on the
external walls, the area of consolidated earth filling over which the apron is
to be constructed should be treated with chemical emulsion @ 5 litres per sq.m.
prior to the construction of the apron.
Treatment of soil surrounding pipes and
conduits:
In case some pipes or conduits enter the soil inside the area of
foundation or come in contact with the soil on the external periphery of the
building, the sol surrounding pipes/conduits should be treated with chemical
emulsion for a distance of 150 mm. and 300 mm respectively from the point of
entry in the inside/outside area.
Treatment of expansion joints:
As a special precaution, the expansion joints are given additional
treatment by applying chemical emulsion @ 2 litres per linear metre after the
subgrade for floor on either side of expansion joints has been laid.
POST CONSTRUCTION TREATMENT
This treatment is applied to existing buildings which have already been
attacked by termites. It is observed that even after their entry in the building,
the termites maintain regular contact with their nest in the ground. This
important symptom is gainfully utilised in eradicating termites from the
buildings. Regular inspection and suitable control measures are necessary to
prevent damage to buildings from termites. At times when the termites attack is
of minor nature it may only be necessary to break off the shelter tubes to
check the damage from termites. In situations, where the attack is of mild
nature the effected materials may also be removed along with shelter tubes. In
case of severe attack, it is necessary to poison the soil around and beneath
the building besides resorting to the above steps. Thus the type of treatment
to be given to be given to eradicate termites from the existing building will
largely depend upon the extent of attack and the magnitude of cellulosic and
other materials available in the building. The various operations involved in
eradicating termites from an existing building can be summarised as under:
1.Inspection:
Inspection is essentially carried out to estimate the magnitude of spread
of the termites infestation in the building and also to detect the root of the
entry of termites and the zones in the building which are attacked. The portion
of the building in contact with or adjacent to the earth should be inspected
first. This includes basements, ground floor, steps leading from ground, walls,
columns, areas having damp or humid conditions like bathrooms, lavatories,
leaking pipes or drains etc. and the places where wood work is embedded in the
floor or wall. The ceilings, wooden panelling, battens for wiring conduits are
other locations which serve as hide out for the termites and need careful
inspection.
2. Soil treatment for foundation:
This treatment consists in treating the soil under the building and
around the foundations with some chemical emulsion which can kill or repell
termites. In this treatment about 500 mm. deep trenches are made along the
external peripheral wall of the building with the help of shovel and 12 mm dia
to 18 mm dia holes are then made in the trenches close to the wall face with
the help of iron rod. The holes should preferably extend up to the top of
footing of foundations or to a depth of at least 500 mm. whichever is lesser.
The holes are then filled with chemical emulsion in water and the back fill
earth is also sprayed with the chemical emulsion as it is returned to the
trench thereby creating a barrier of poisoned soil along the external periphery
of the building. The total quantity of the chemical to be used in this
treatment should be @ 7.5 litres per sq.m. of the vertical surface of the
masonry in foundation.
In case of R.C.C frame structure, the chemical treatment shall be applied
to the soil in contact with column sides and plinth beams along external
periphery of the building for a depth of 500 mm below ground level.
In case the building has masonry or concrete apron, about 12 m dia holes
at 300 mm centres should be drilled close to the plinth wall along the apron.
The holes should be deep enough to reach the soil below. Chemical emulsion
should thereafter be pumped into these holes @ 2.5 litres per linear metre of
the length of the apron.
3. Soil treatment under floor:
Cracks in floors are the weak spots which permit entry of termites from
soil below the floor. The cracks usually occur at the junction of the floor and
walls, expansion joints in floor and at construction joints in a concrete
floor. Cracks in floors may also develop due to use of unsound materials or on
account of defective workmanship. In such cases eradication of termites is
achieved by poisoning the soil underneath the floors wherever such cracks are
noticed. This operation is generally carried out by drilling 12 mm dia holes at
300 mm centre to centre all along the cracks in the floors in different areas
and then injecting chemical emulsion into the holes till the soil below gets
fully saturated. The maximum quantity of chemical emulsion may, however not
exceed one litre per hole. The holes in floors are scaled after treatment.
4. Treatment of voids in masonry:
It has been seen that termites enter into masonry foundations from soil
adjacent/beneath the building and work their way up through voids in masonry
joints and gain entry into the interior of the buildings. To prevent the entry
of termites through voids in masonry joints and gain entry into the interior of
the buildings. To prevent the entry of the termites through voids in masonry,
12 mm dia holes at 300 mm centre to centre are drilled at downward angle of
about 45 from both sides of walls at plinth level and then chemical emulsion is
pumped into the holes until masonry gets fully saturated with the chemical
emulsion. The holes are then sealed. This treatment is carried out for all
walls having foundation in soil. Treatment of drilling hole and pumping chemical
emulsion should also be carried out at critical locations like wall corners and
at places where door and window frames are embedded in masonry in ground floor.
5. Treatment of wood work:
Wood work which is badly damaged by termites should be replaced by new
timber which is adequately brushed or dipped in oil or kerosene based chemical
emulsion. The infested wood work for door and window frames, etc. should be
given protective treatment by drilling 6 mm dia holes at 150 mm centre to
centre at a downward angle of 45 to cover the entire frame work and thereafter
pumping oil based chemical emulsion into the holes. The wood work which is not
attacked by termites should be sprayed over with chemical emulsion to prevent
possible attack.
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