ANTI-TERMITE WORK



ANTI-TERMITE WORK

3.0. General - Anti-termite treatment is divided into three parts, namely,

(1) Anti-termite treatment by chemical methods.

(2) Anti-termite treatment through constructional means, and Anti-termite treatment of existing buildings.

3.1. SpecificationsS for Anti-termite Chemical treatment

3.1.1 Termites are divided into two types on the basis of their habitat, namely (a) Subterranean or ground-nesting termites, and (b) Non-subterranean or wood-nesting termites having no contact with soil.  The former are more destructive.  Treating the soil with chemicals beneath the building and around the foundation with a chemical soil insecticide is a good preventive measure.  The purpose of the treatment is to create a chemical barrier between the ground and wood work.  Of course, timber used in the building shall be natural, durable, heartwood, treated and seasoned.

Anti-termite treatment can also be given, through constructional measures, to existing buildings. These are covered elsewhere in clause 3.3.

3.1.2. Site preparation. - Remove trees, stumps, logs or roots, which may be harbouring the termites. On clays and other heavy soils where penetration is likely to be slow and on sloping sites where run off of the treating solution through piping or excessive percolation is likely to occur, the surface of the soil should be scarified to a depth of at least 75 mm.

On loose and porous or sandy soils where loss of treating solution through piping or excessive percolation is likely to occur, preliminary moistening to fill capillary spaces in the soil is recommended.

All sub-floors leveling and grading shall be completed.  All cuttings, trenches and excavations should be completed with back filling in place.  Borrowed earth fill must be free from organic debris and should be well compacted.  All frameworks, leveling pegs, timber off cuts or other builders’ debris should be removed from the area to be treated.

3.1.3 Treatment beneath the building - For treating soils beneath a building, the following chemicals are effective:

  1. Heptachlor emulsifiable concentrate 0.5 percent by weight, ( see IS 6439 : 1978);
  2. Chlordane emulsifiable concentrate 1.0 percent by weight  ( see IS 2682 : 1984);
  3. Chloropyrifos emulsifiable concentrate, 1.0 percent by weight (see IS 8944: 1978).

Notes-1.  These chemicals are to be regarded as POISONS.  They can have adverse effect on health when absorbed through skin, inhaled as vapours or spraymists or swallowed.  Therefore, they must be safely handled [see Appendix B of IS: 6313(Part2)-1981.  These chemicals should not be used where there is a risk of walls or other water supplies being contaminated.  The authority concerned shall be consulted.

2.  Aldrin has been banned by Government of India.  Before use of these chemicals latest recommendations of Central Insecticide Board and Registration committee, Ministry of Agriculture, Faridabad should be referred. 

Where there are mounds of termites within the excavated area, these chemicals shall be poured into the mounds at several places after breaking them.  The quantity used shall be related to the size of the mound.  For a mound of about 1 cm3, 4l of the emulsion of one of the chemicals may be used, namely, 0.25 percent Heptachlor emulsifiable concentrates. 0.5 percent Chlordane emulsifiable concentrates.

3.1.4 Time of application - Soil treatment should start when foundation trenches and pits are ready to take mass concrete in foundations.  Treatment should not be carried out when it is raining or when the soil is wet.  This also applies to filled up soil within plinth area before laying the subgrade for the floor.

3.1.5 Treatment of masonry foundations and basements - The bottom surface and sides (up to about 30 cm) of the excavations made for necessary foundations and basements shall be treated with the chemical at the rate of 5l/m2 of surface area.

After the masonry foundations and retaining wall come up, the backfill in immediate contact with the foundation shall be treated with the chemical at the rate of 7.5l/m2 of the vertical surface of the sub-structure for each side.  If water is used for ramming the earth fill, the chemical treatment shall be carried out after the ramming operation is done.  For this rodding of earth close to the wall at 15 cm centres shall be done and working the rod backwards and forward parallel to the wall before applying the chemical emulsion.

Fig 1 Treatment for masonry foundations without apron. 

The earth fill is done in layers and the chemical treatment shall be carried out for each layer.  After the treatment the earth should be tamped in place.  The chemical emulsion shall be directed towards the masonry surfaces in contact with the earth.  All foundations shall be fully surrounded by and in close contact with the chemicals treated soil barrier (see Fig.1 and Fig.2).

3.1.6 Treatment of RCC foundations and basements-The treatment of masonry foundations was necessary because of the voids in joints through which the termites are able to seek entry into the building.  However in RCC foundations there are no such voids for the termites to penetrate.  It is therefore unnecessary to start the treatment of RCC foundations from the bottom.  The treatment may be started at 500 mm below ground level except when the level is raised or lowered by filling after the foundations have been cast.  In such a case the depth of soil level shall be determined from the new

Fig 2 Treatment for masonry foundation with apron along external perimeter ground level.  The soil in the immediate contact with RCC shall be treated with 7.5 litre/m2 of the chemical.  The other details are as in Fig.3.

3.1.7 Treatment of top surface of plinth filling

The top surface of the consolidated earth within plinth walls shall be treated with chemical emulsion at the rate of 5litre/m2 of the surface before the sand bed or sub-grade is laid.  If the filled bed is rammed and the surface does not allow the emulsion to seep through, holes up to 50 mm to 75 mm deep at 150 mm centres both ways may be made with 12 mm steel rod to facilitate saturation of the soil with chemicals.

3.1.8 Treatment at junction of the wall and the floor - Special care shall be taken to establish continuity of the vertical chemical barrier on the inner wall surfaces from ground level A (or other level) up to the level of the filled earth surface.  To do this, a small channel 30 mm x 30 mm shall be made at all the junctions of wall or columns with the floor (before laying sub-grade) and rod holes made in the channel up to the ground level 150 mm apart; the rod shall be moved backward and forward to break up the earth and then the chemical emulsion be poured along the channel at a rate of 7.5litre/m2 of the vertical wall or column.  This would permit the soil to be soaked right down to the bottom.  The soil should tamped back into place after the operation.

Fig 3 Treatment for RCC foundations

3.1.9 Treatment of soil along external perimeter of the building - After the building is complete, the earth along the external perimeter of building shall be rodded at intervals of 150 mm to a depth of 300 mm.  The rod should be moved backward and forward parallel to the wall to break up the earth and the chemical emulsion is poured along the water at the rate of 7.5litre/m2 of the vertical surfaces in contact with earth.  After the treatment the earth should be tamped back into place.  If the earth outside the building is graded the treatment should be carried out on completion of grading. 

In the event of the filling being more than 300 mm, the external perimeter treatment shall extend to the full depth of filling down to the ground level so as to ensure continuity of the chemical barrier. 

3.1.10 Treatment of soil apron along external perimeter of building - The top surface of the consolidated earth over which the apron is to be laid shall be treated with chemical emulsion at the rate of 5 litre/m2 of the surface before the apron is laid.  If the consolidated earth does not allow the emulsion to seep through, holes up to 50 mm to 75 mm deep at 150 mm centres both ways may be made with 12 mm dia rod, on the surface to facilitate saturation of the soil with the chemical emulsion ( see fig.2).

3.1.11 Treatment of walls retaining soil above ground level - Retaining walls like basement walls or outer wall above the floor level retaining soil need to be protected by providing a chemical barrier so as to prevent entry of termites through voids in masonry, cracks, etc.  The soil retained by the walls shall be treated with the chemical emulsion at the rate of 7.5 litre/m2 the vertical surface in contact with the soil.  This barrier should be in continuation of the barrier up to the plinth level. 

3.1.12. Treatment of soil surrounding pipes, conduits, etc- When pipes, conduits, enter the soil inside the area of the foundations, the soil surrounding each point of entry should be treated.  For this the soil shall be loosened for a distance of 150 mm and depth of 75 mm and then the treatment should be commenced at the same rate as the foundation soil. When the pipes enter the soil external to the foundations they shall be similarly treated for a distance of 300 mm unless they are clear of the walls by about 75 mm.

3.1.13 Treatment of expansion joints - Expansion joints at ground level are one of the worst hazards for termite infestation.  The soil beneath these joints should receive special attention when treatment under 3.1.6 for plinth filling is being carried out.  This treatment should be supplemented by treating the expansion joint after the sub-grade has been laid, at the rate of 2 litres per linear meter. 

3.1.14 Treatment of voids in masonry- The movement of termites through the masonry walls may be arrested by squirting chemical emulsion through holes drilled in the wall at plinth level.  The holes shall be drilled at a downward slope of around 45°.  This treatment shall also be done to internal walls in contact with soil.  Additional holes may also be drilled as needed, such as, wall corners, under door and window frames, etc.  The treatment holes shall then be sealed.

3.1.15 Treatment at points of contact with woodwork- All existing work, infested with termites, shall be treated by spraying at points of contact with masonry with chemical emulsion in holes drilled at an inclination of around 45°, the rate shall be around half-a-litre per hole.

3.1.16 Treatment of woodwork

(1). Woodwork, which has been damaged beyond repair, shall be replaced after appropriate treatment.

(2). Infested woodwork, which can be used, shall be protected with chemical treatment squirted through inclined holes drilled into the woodwork up to the core, on the unaffected side of the frame.  If need be, the woodwork may be painted with one or two coats of chemicals.

3.1.17 Treatment of electrical fixtures - Wherever possible, the inside of the enclosures of electrical fixtures shall be treated liberally with chlordane powder.

3.2. SPECIFICATIONS FOR ANTI-TERMITE TREATMENT THROUGH CONSTRUCTIONAL MEANS

3.2.1 Termite control in buildings is very important, as damage likely to be caused by the termites is huge.  Termites attack both cellulosic and non-cellulosic materials.  They also damage materials of organic origin with a cellulosic base.  Wood, rubber, leather, plastic, neoprene as well as lead coating used for covering underground cables are damaged by termites.

3.2.2 There are two types of termites, namely, subterranean, or ground nesting termites and non-subterranean termites or wood nesting which have no contact with soil.  The subterranean termites cause most damage in buildings.

3.2.3 Prevention of possible invasion by subterranean termites from the ground to the building through external entry or internal attack from under floors should be undertaken. This can be done either by preventive-cum-detection methods, for example, masonry groove or termite shield or string course and cement concrete apron floor ; or by internal preventive methods, such as, by providing a solid floor.  The constructional methods given in this part are based on actual basis trials in the field but modifications due to local conditions have to be made.

3.2.4 Preliminary work

3.2.4.1 Presence of termites - The presence of termites at the site may be determined either by experience of local inhabitants or by stake test as described below. A number of stakes 50 mm x 50 mm of timber species which are susceptible to termites, such as, chir, kail, mango, etc, should be buried at least 150 mm into the ground spaced at 1 m centre-to–centre at the proposed site.  After 3-4 months, the stakes may be taken out and infestation of termites observed.  Termites, if present, will damage the stakes.

3.2.4.2 Clearance of site - Care shall be taken to see that all wooden debris, roots, leaves, stumps and other organic matters are not accumulated or buried near the foundation or under floor of the building.  Typically termite nests are formed in a stump or other piece of timber near the site.  If the soil is covered by soil rich in decaying matter, the top layer of the soil (about 50-100 mm) shall be removed.  The soil shall be graded to maintain drainage around the building.

3.2.4.3. Elimination of moisture - Drainage shall be ensured so that water does not accumulate or stagnate around the building.  Access of water to the underside of the ground floor shall be prevented through proper construction measures, such as, construction of concrete apron around the building.

3.2.4.4 Foundation and sub-base of ground floor:

  1. Every effort should be made to avoid voids in the construction of foundations.
  2. The earth and sand filling around the foundations and in sub-base shall be fully rammed so as to prevent any subsidence in soil.
  3. Where jointless sub-base is not possible, precautions may be taken to prevent crack formation and the joints are sealed.
  4. If concreting of sub-base has to be resumed on a surface which has hardened, such surfaces shall be roughened, swept clean, thoroughly wetted and covered with a 15 mm layer of mortar composed of cement and sand in the same ratio as in the concrete mix.  This layer of mortar shall be freshly mixed and laid immediately before placing of concrete.  When concrete has not fully hardened, all laitance shall be removed by scrubbing the wet surface with wire or bristle brushes, care being taken to avoid dislodgement of particles of aggregates.  The surface shall be wetted and all free water removed and then coated with neat cement grout.  The first layer of concrete to be laid shall not be more than 150 mm in thickness and shall be well rammed against old work, particular attention being paid to corners and close spots.

3.2.4.5 Selection of timber - Seasoned timber which is naturally durable in heartwood and which is treated to withstand the attack of subterranean termites should be used in the building (see IS: 40-1982 and IS: 1141-1993, on preservation and treatment of timber).

3.2.5 Design criteria

  1. Anti-termite measures through construction will be effective if both external and internal protection is adequately provided. The external protection refers to prevention of termite access on surrounding area of the building.  The internal protection refers to the access from soil under the floor area.
  2. For external protection, provision of metal shields or masonry grooves around the periphery of the building and cement concrete apron around the building are recommended. To be effective the shape of the metal barrier shall be properly maintained.
  3. For internal protection the concrete sub-base shall be extended under the walls so that the entire plinth area is fully covered without any break.  In case of depressed floors like lift wells, bathrooms, garage pits, etc, the sub-base should be continuous.
  4. The concrete flooring shall be laid over a layer of coarse sand (larger than 3 mm) as the sand layer checks soil moisture rising up.
  5. Termites do not generally penetrate masonry or concrete in which there are no voids.  Masonry with lime mortar mix leaner than 1:3 shall not be used to be in contact with soils.  If the floor construction gives rise to vertical joints between the floor and the plinth masonry, the joints may be filled with heavy grade coal tar pitch conforming to IS 216 : 1961 to minimize the tendency of termites to infiltrate through these joints.

3.2.6 SPECIFICATIONS FOR INTERNAL AND EXTERNAL ANTI-TERMITE MEASURES 

3.2.6.1 Construction methods - The construction methods as specified may be adopted for protection against subterranean termites originating both internally from within and  externally from the area surrounding the building.  Stagewise details are given.

3.2.6.2 Earth, free from roots, dead leaves, or other organic matter, shall be placed and compacted in successive horizontal layers of loose material not more than 200 mm thick. Dry brick shall be inserted at least 50 mm in brick masonry for providing apron floor around the periphery (see Fig. 4.)

3.2.6.3 Brick on edge in cement mortar shall be laid on the plinth wall.   Dry brick shall be placed on the inner side of the plinth wall for getting anticipated offset space for coarse sand and on the other side for installing anti-termite masonry groove.  In the case of intermediate walls, dry bricks are placed on either side of the brick on edge masonry for getting offset space for coarse sand layer (see Fig. 5).

3.2.6.4 The dry brick for the anti-termite groove shall be taken out and cement concrete (1:3:6) sub-floor shall be laid casting an anti-termite groove in position.  In case of internal protection walls, the cement concrete sub-floor shall be laid on either side over dry bricks to sufficient extent for getting staggered vertical joints over the joint of plinth wall and earth filling (see Fig. 6.)

3.2.6.5 Superstructure masonry shall be raised over the cement concrete sub-floor and overhead jobs completed (see Fig. 7).

3.2.6.6 The dry brick for coarse sand filling shall be removed and graded sand (of size 4 mm to 5 mm) layer at least 100 mm thick shall be compacted over the earth filling (see Fig. 8).

3.2.6.7 Cement concrete (1:3:6 mix) sub-floor at least 75 mm thick shall be laid over the sand filling.  Masonry finish may be provided to the cement concrete sub-floor (see Fig. 9).

3.2.6.8 Dry brick provided for apron floor (see Fig. 1) shall be taken out and 600 mm wide formation of earth of 1:30 slope shall be made.  Over the formation 75 mm thick lime concrete (1:3:6 mix) shall be laid (see Fig. 10).

3.2.7 SPECIFICATIONS FOR TERMITE SHIELDS

3.2.7.1 Installation - Termite shields may be installed around the periphery of a building where infestation is high.  Provision of metal shields takes care of external protection only.  The visible termites tunnels on the shields should be destroyed periodically. However, termite metallic shield in residential areas may be hazardous for people; so it may be advantageously used for warehouses, godowns, etc.  Metallic sheets may be made out of galvanized sheets, aluminium sheets, etc.  The sheet should be embedded in the sub-floor properly with about 50 mm projection bent downward around 45 degree (see Fig. 13).  The free edge also may be turned downwards as termites can negotiate on straight edge.

General protective measures shall be attempted for door entrances as it is not practicable to install metal shields.

3.2.7.2 Termite caps - Inverted caps may be used in pipelines outside walls to prevent migration of termites and they should be properly mounted.

3.3 SPECIFICATIONS FOR ANTI-TERMITE TREATMENT IN EXISTING BUILDINGS

General

3.3.1 Preventive chemical treatment against termites in the soil Part 1, dealt with constructional means of preventing termite attack.  This part deals with treatment after attack in existing buildings.

3.3.2 Post construction treatment

3.3.2.1 Inspection - Before undertaking any type of treatment, a thorough inspection shall be made of the infestation in the building with a view to determine the extent to which it has spread and the routes of entry of the termites into the building.  A study of the structure of foundation and the ground floor helps in finding out the routes of entry of termites from the soil and also in deciding on the mode of treatment.  For guidance, information on detection of termites is given in Annexure 3-A.1

3.3.2.2 Extermination of termites in buildings - After making a study of the infestation in the building the next step is to eliminate the termites located inside the building. This shall be carried out in a thorough manner, seeking the termites in their hideouts, such as, ceilings, behind wooden panelling, inside electrical battens, conduits, switchboards and similar locations.  Recourse may be taken to inject chemicals as already mentioned in 3.1 along with the recommended concentrations; every precaution shall be taken while using chemicals to protect the operators. All traces of termite tubes shall be removed so that any fresh infestation which might occur at a later date may be easily detected. The chemicals to be used are Heptachlor 0.5 percent emulsifiable concentrate, 1.0 per cent Chlordane emulsifiable concentrates and 1.0 per cent Chloropyrifos emulsifiable concentrate. The Authority concerned with the use of pesticides should be consulted on the hazards in using these chemicals.

3.3.3 Preventive measures

3.3.3.1. Soil treatment -The object of soil treatment is to establish chemical (toxic) barrier between termites in the soil and the building to be protected.  Basically it consists of treating the soil adjacent to or under the building with a chemical toxicant which kills or repels termites. Water emulsions of any one of the chemicals as mentioned shall be used in soil treatment and applied uniformly at the prescribed rate.

3.3.3.2 Treatment along outside of foundations

  1. The soil in contact with the external wall of the building shall be treated with the chemical emulsion at the rate of 7.5 l/m2 of the vertical surface of the substructure to a depth of 300 mm.
  2. To facilitate this treatment a shallow channel shall be excavated along and close to the wall face.
  3. The chemical emulsion shall be directed towards the exposed wall at the rate of 1.75 litres per running meter of the channel (see Note).

Note: - 7.5 l/m2 for a depth of 0.3 m means 2.27 litres per running meter.

  1. For uniform disposal of the chemical, rodding may be done at every 150 mm intervals.
  2. The balance of the chemical (2.27 – 1.75 l/m) shall be used to treat the back fill returned to the channel.
  3. If there is a concrete apron around the wall, instead of excavating a channel, holes shall be made in the apron 800 mm apart and deep enough to reach the soil below and then the chemical solution be pumped at the rate of about 2.25 litres per running meter.
  4. The treatment mentioned here applies to masonry foundations.

3.3.3.3 In the case of RCC foundation, the soil (backfill) in contact with the column sides and plinth beams along the external perimeter of the building shall be treated with the chemical solution at the rate of 7.5 l/m2 of vertical surfaces of the structure.  Details of the treatment shall be as above.

3.3.4 Treatment of soil under floors-The points where termites are likely to seek entry through the floor are the cracks at the following locations:

  1. At the junction of the floor and walls as a result of shrinkage of the concrete;
  2. On the floor surface owing to construction defects; and
  3. At expansion joints in the floor.

The method of the dealing with these locations is to apply chemical treatment within the plinth wherever such cracks occur.  The chemical should be pumped through holes drilled at regular intervals to a reasonable depth, until refusal, subject to maximum of one litre / hole.  The holes shall then be sealed.

3.3.5 Treatment of voids in masonry -The movement of termites through the masonry walls may be arrested by squirting chemical emulsion through holes drilled in the wall at plinth level. The holes shall be drilled at a downward slope of around 45 degree. This treatment shall also be done to internal walls in contact with soil. Additional holes may also be drilled as needed, such as, wall corners, under door and window frames, etc. The treatment holes shall then be sealed.

3.3.6 Treatment at points of contact with wood work -All existing work, infested with termites, shall be treated by spraying at points of contact with masonry with chemical emulsion in holes drilled at an inclination of around 45 degree Celsius, the rate shall be around half-a-litre per hole.

3.3.7 Treatment of wood work

  1. Wood work which has been damaged beyond repair shall be replaced after appropriate treatment.
  2. Infested wood work, which can be used, shall be protected with chemical treatment squirted through inclined holes drilled into the wood work up to the core, on the unaffected side of the frame.  If need be, the wood work may be painted with one or two coats of chemicals.

3.3.8 Treatment of electrical fixtures - Wherever possible, the inside of the enclosures of electrical fixtures shall be treated liberally with chlorodane powder.

3.3.9 Inspection - Periodic inspection of the work/installations particularly during humid and hot seasons would be helpful.

Guide for Termite Detection

Procedure: Bright light is essential for termite detection. A bright hand-held electric bulb (in a fixture) or a torch would be necessary.

Portions of the building in contact with or adjacent to soil should be inspected.  Damp locations, such as, bathrooms, etc, shall also be inspected.  Points where wood work is embedded in the floor, in particular, shall be examined.

The signs of presence of termites is through the tell tale tubes. Termites travel in these and are supposed to eat away wood work leaving the film of paint on the surface, making it difficult to locate the termite.  Wood work should be tapped to check hollow sound which would indicate termite attack. The new tubes of termites are moist; the old ones are dry and break easily.  These must be gouged out with a knife to destroy the termites.

*****