ANTI TERMITE TREATMENT
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 : Dry wood termites Subterranean 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 building and its erring can or hand operated compressed air sprayer can be used. The soil treatment should be applied in the following stages :
Treatment of wall trenches column pits and excavation for basements :
• The bottom surface and the sides (Upto a height of about 3000 mm) 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
The treatment described above is essentially required to be given to masonry foundation with a view to ensure that the termites do not gain entry into the building through the voids in the joints in the masonry.
In case 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 basement walls from a depth of 500 mm upto ground level only should be treated with chemical emulsion @ 7.5 per sq.m of vertical surface.
Treatment of top surface of plinth filling
Prior to laying the sand bed or sub-grade for the ground floor of the building, top surface of the consolidated earth filling within the plinth walls should be leveled 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 floors require special attention to ensure effective soil treatment. For this it is important to establish vertical continuity of the poisoned soil barrier on inner 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 plinth. Holes are thereafter made in the channel at 150 mm apart upto 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 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 (parallel to the external wall) 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 condiuts enter the soil inside the area of foundation or come in contact with the soil on the external periphery of the building, the soil surrounding pipes/conduits should be treated with chemical emulsion for distance of 150 mm and 300 mm respectively from the point of entry 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 sub-grade for floor on either side of expansion joints has been laid. This treatment is in addition to the treatment which is necessarily provided to the structure upto top of consolidated earth fill within plinth in accordance with treatment of top surface of plinth filling.
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 utilized 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 eradicate termites from the existing building will largely depend upon the extent of attack and magnitude of celluosic and other materials available in the building.
The various operations involved in eradicating termites from an existing building can be summarised as under :
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 include 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, switch boards are other locations which serve as hide-out for the termites and need careful inspection.
In case of multi-stored buildings, lift wells, casings covering electrical wiring telephone cable, water supply and soil pipes which serve as convenient and well protected zones for termites infestation should also be inspected carefully.
Wherever the mud walled shelter tubes or the termite runways are detected, they should be removed. Wherever possible, oil or kerosene based chemical emulsion should be injected over the attacked areas of wood work and masonanry. At times, structural additions may become necessary to ensure elimination of all direct contacts between the soil and the effected portion of the structures.
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 repel termites. In this treatment about 500 mm deep trenches are made along the external peripheral wall of the building with the help of shovel (width of the trench being equal to the width of the shovel) and 12 mm dia to 18mm dia holes at 150 mm centres are then made in the trenches close to the wall face with the help of iron rod. The holes should preferably extend upto the top of footing of foundations or to a depth of atleast 500 mm whichever is lesser. The holes are then foundations or to a depth of atleast 500 mm which ever is lesser. The holes are the 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 @ 75 litres per sq.m of the vertical surface of the masonry in foundation.
In case of RCC 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.
Soil treatment under floor
Cracks in floor 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 a 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 sealed after treatment.
Treatment of voids in masonry
It has 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 the termites through voids in masonry, 12 mm dia holes at 300 mm centre to centre are drilled at downward angle of about 450 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 (both internal as well as external) 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.
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 450 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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