|Table of Contents|
Table of Contents
Introduction and how to recognize termites and their work
Conditions that favor termite infestation in buildings
Prevention of infestation by termites
Control of infestation by termites
List of companies handling chemicals and pressure treated wood
List of publications on termites and their control
LIBRARY ~fAll7 PLANT 8OARD
INSECTS IN RELATION
AGRICULTURE BIAAU OF ENTOMOLOGY AND p PLANT QUARNTINE
Digitized by the Internet Archive in 2013
INSECTS IN RELATION
Circular 2 Termites
Table of Contents
How to Recognize Termites and Their Work........... 2
Conditions That Favor Termite Infestation in Buildings. ........................ ....00....eooon6Oi
Prevention of Infestation by Temts....... 7
Do Not Leave Wood inSoil.....................
Avoid Contact Between Wood and Soil...........
Clearance and Ventilation..................... 8
Grading and Drainage..........................
Porches and Terraces............................. 13
Exterior Woodwork................................ 18
Wood;Used inBasements........................... 19
Water' Pipes, etc.............................. 21
Concrete Platforms or Ground Slabs............... 21
Use of Pressure-treated and Naturally Resistant
Use of Metal Termite Shields..................... 24
Periodic Inspections............................. 30
Control of Infestation byTerites................. 30
Primary or Structural Control Methods............ 33
Mechanical Blocking with Concrete or Masonry... 33
Mechanical Blocking with Metal Aprons or
Soil Poisons................................. 34
Precautions to Avoid Injury to Animals and
Methods of Application........................ 36
Exposed Foundation......................... . 36
Enclosed, Filled, or Unfilled Porches........ 37 Ground Slabs of Concrete or Masonry.......... 38 List of Companies Handling Chemicals and Pressure Treated onTermites.and.their Con.ro. 39
List of Publications on Termites and their Control* 42
Circular 2 -a Termites 2
The prevention of damage, by termites will be an important problem to be solved in connection with the construction and maintenance of the thousands of buildings used in the National defense Program* Past experience has shown that unless special attention is given to
this problem, both in the design and during the construction of buildings, these insects are almost certain to cause damage within a comparatively short time, Such damage may even occur within the first few months where optimum conditions for infestation exist and where there is a high termite Dopulation in the soil at the time construction begins. This damn e can invariably be traced to certain construction details or practices which are in common use, or to carelessness and lack of knowledge regarding conditions favorable to termite infestation*
Most of the termite damage to buildings in the
United States is caused by subterranean or ground-nesting termites (Reticulitermes spp,)o They feed upon wood and other materials contafETng cellulose and are destructive pests in buildings in which wood is used. They will not normally infest buildings unless they can maintain contact with moisture in the soil, and this requirement must be kept continually in mind if control or preventive measures are to be successful*
HOW TO RECOGNIZE TERMITES AND THEIR WORK
Termites are small soft-bodied insects about onefourth inch long when mature. The workers (f ig. 1) are about one-sixteenth inch wide, slightly less in height, and can thus crawl through cracks or very small openings. They may be easily distinguished from true ants by the fact tnat they do not have the strongly constricted waist-line that is characteristic of all ants. A subterranean termite colony contains three forms or castes.workers, soldiers and reproductive, 1112e workers and soldiers are without wings and are creamy-white in color
Circular 2 Termites
Figures 1 and 2 respectively. Worker and soldier termites. Enlarged about 12x.
Figures 3 and It respectively. Winged termite and ant.
Inlarged about 4x. Note shape of bodies and sise of
Circular 2 -Termites
and somewhat similar in appearance except that the soldiers have very large heads and large marndibles or jaws (fig. 2). Both of these forms lead a concealed life within their tunnels in wood and soil. The reproductives have brown or black bodies and are provided with
two pairs of wings of equal size. The reproductive forms among the true ants also have two pairs off wings but these pairs are of unequal size (figs. 3 and 4),
bers Large numbersof.reproductive termites emerging from the soil or wood early If in the spring or
during the summer months may be the
first indication 41 of the presence of
A, a termite colony.
At this time they pair of f and each pair attempts to find a new location for starting a new colony. Whden they emerge within a building they are attracted by strong 1li it an d will gather about windows or doors in an endeavor to get outside. They soon shed their wings and
then try to return to the soil. Winged subterranean termites do not damage wood; only the workers do this.
Termite damage 7 igure 5.Siding removed from to wood is not often
building to reveal hidden attack evident from the exin wood. tenor (fig. 5). The
workers avoid free
Circular 2 Trmi tes 5
exposure to the air and therefore construct their galleries within the wood or other cellulose-containing materials which they attack, They occasionally completely honeycomb wooden timbers, leaving only a thin shell, The inside of their galleries is covered with grayish specks of excrement anai earth, Subterranean termites do not reduce the wood to a powdery substance or push wood particles to the outside through openings as do certain other types of insects.
Termite infestation may also be evidenced by the presence of earth-like shelter tubes or covereA runways which the termites may construct over the surfaces of foundation walls or other materials that they are unable to penetrate (fig. 6). rhese tubes vary in size and
Figuir..6. Shelter tubes made over imponetreble foundation
vall in poorly ventilated basementless area beneath a building. In this Instance infestation occurred beyond the point
shown In the picture. Many tubes are being extended down.
ward from the structurally da sedI sill to the ground to
Circular 2 1ermites 6
shape but often are about the diameter of a pencil and are slightly flattened, They serve as covered passageways between the wood and the essential moisture in the soil, and protect thie termites from the drying effect of direct exposure to the air (fig. 7).
CONDITIONS THAT FAVOR TIER4ITE iNiESTATI0N IN BUILDINGS
Subterranean termites become most numerous in
moist, warm soil containing an abundant supply of food in the form of wood or other cellulose material. Such
conditions are often found beneath buildings where the space below the first floor is poorly ventilated and where scraps of lumber, form boards, grading stakes
or other wood are left tt; in the soil (fig. 8).
I Soil within or adjacent to heated basements is
kept warm throughout most of the year, even in northern areas, and results in prolonging the normal period of activity.
Probably 90 percent of all termite infestations in buildings occur because of wood
being in direct or indirect contact with the ground, 6such contact usually will be found at
- ----porches, steps or terraces (fig. 8). Cracks Pigur. 7. Portion of tube show on or voids in foundations inner side of masonry wall within also make it easy for baseuientless foundation, Worker termites to reach wood termites are exposed by breaking that is not in actual away a part of the tube, contact with the soil.
Circular 2 Termites 7
The species of termites that are common in the United States rarely build shelter tubes upward on exposed exterior faces of foundations to reach wood above, Underneath buildings upward tubing is uncommon on surfaces of foundations except under conditions of poor ventilation and moist soil which result in high humidity and are conducive to greater termite activity,
PREVENTION OF INFESTATION BY TERMITES
Experience has shown that certain faulty practices in the design and construction of buildings are responsible for most of the damage caused by termites. In perhaps the majority ol cases, nese practices result fromignorance of, or indifference to, the danger of termite infestation, The following suggestions are made with the objective of encouraging design and construction practices which will give effective protection against infestation as well as embody goud principles from the standpoint of the architect and builder.
Effective protection against infestation by termites can be assured by careful observance of the following practices in all construction work:
1, Remove all wood debris and other cellulose
material from the building site,
2, Avoia all direct or hidden contacts (i.e.
through voids or cracks in the foundation)
between woua and soil or fill.
3* Provide adequate clearance, ventilation and
soil drainage beneath all parts of the building.
Prevent upward tubing by termites on foundation surfaces by inspection for the removal
of tubes or by the use of shields when necessary,
These broad generalizations are elaborated and
defined in the following pages*
Circular 2 Term.1t.es
Do Not Leave Wood in Soil
All tree roots, stumps or other wood debris
should be removed from the building site before construction work is started. Form boards and all scraps of lumber should be removed before filling or backfilling after
the foundation is completed. This is particularly important in the case of filled porches, terraces and steps (fig. 8 ). Spreader sticks and grading stakes should be pulled before the concrete sets. In the'case of buildings without basements, scraps of lumber should not be allowed to remain on the surface of the soil beneath the buildings. If no wood is left in or on the soil the danger of a large population of termites developing in the soil and later attempting to infest the building is prevented (fig. 9 ).
Avoid Contact Between Wood and Soil
No wood used in the building should be placed in direct contact with the soil or f ill. This is very important as a means of avoiding damage by decay as well as by termites. All wooden posts, pillars, stair carriages or partitions in basements should be set on concrete footings and should never extend through or into concrete or masonry floors. Outside woodwork, such as steps, should rest on concrete footings or aprons extending at least 6 inches above grade and provided with slope for drainage (fig* 10). Lattices or skirting used to close the spaces between piers should have clearance of
at least 2 inches above the soil and 1 inch from the piers (fig, 11),
Hidden or indirect contacts, through foundation
walls that are not impervious or at points where porches, steps or terraces are attached to buildings, are respons ible for the great majority of infestations and must be
carefully guarded against (fig.
Clearance and Ventilation
A minimum clearance of 18 inches should be required
beneath all joists, girders or other wooden parts of a building (fig-12), In the southern and more humid sections of the country a minimum of 24 or 30 inches is desirable.
Circular 2 Terattoo 9
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Circular 2- Termites 10
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Fi gure 10. SI DE OF PORCH STEPS OPEN, MO0D IF IE D BREAD-PAN SHIELD OVER WALL
Figure 1I. METHOD OF ATTACHING PORCH LATTI CE
TO PREVENT TERMITE DAMAGE
Circular 2 Termites 11
Ventilation space in the foundation wall should be proportioned on the basis of a minimum of 2 square feet of net opening for each 25 linear feet of exterior wall (fig. 13Y. The amount of ventilation required will vary considerably with the location and surrounding conditions. Some authorities recommend a minimum opening equivalent
to 3 percent of the ground area occupied by the building. The openings need not be placed in the foundation on the front side of a building, provided they can be otherwise arranged to prevent any "dead ends" or unventilated areas. Shrubbery should be kept away from the openings for sufficient distance to allow free circulation of air,
Termites and decay thrive best under moist conditions, Every practical measure should therefore be taken to reduce the amount of moisture in the soil and air beneath buildings. The simplest way to attain this objective is to provide ample ventilation and clearance as specified above; the two go hand in hand, as the greater the clearance, the more readily is ventilation obtained. Clearance of less than 18 inches will not give room for
making inspections for termite activity or for applying control measures in case infestations are found.
Grading and Drainage
As stated before, moisture is absolutely essential for termite activity. The outside grade should be kept at least 6 inches below all woodwork and should provide surface run-off to drain the water from the eaves or domn spouts away from the building, thereby aiding in keeping the soil adjacent to the foundation as dry as possible (fig, 12), As a further aid to dryness, buildings with
basements should have drainage tile around the outside of the foundation footings. Likewise, in basementless areas, every effort possible should be made to maintain dryness underneath the building.
Emphasis should be placed on the necessity of.
avoiding the burying of pieces of lumber or other wood material in the soil during the grading operations.
Circular 2- Termites 12
Grade Eo 00Figure 12. BREAD-PAN SHI ELD OVER WALL
Figure 13. LOUVRED VENTILATOR
FOR BASEMENTLESS AREA
Circular 2 -Termites 1
The use of impervious foundations is fundamental to 'prevention of damage by termites. Such foundations present an effective barrier to the passage of termites upward through the walls or piers from the soil to wood above. If termites are to reach wood they are forced to construct shelter tubes over the surfaces of such walls or -piers. As indicated above, upward tubing is not common in most areas where proper ventilation is provided. Periodic inspection will reveal any tubes that may be constructed and they can be destroyed and control measures can be applied if necessary.
Poured concrete foundation walls or piers should be used wherever possible. All points of stress should be reinforced with steel rods to prevent cracking. Unit
masonry should have the joints well filled with Portland cement mortar and should be capped with a minimum of 4 inches of plain or 2 inches of reinforced concrete, so
that in case termites work their way up through or between the units they will be forced out into the open where inspection wiill reveal them before they reach wood above (f1ig.26J.
Where the use of wooden piers or posts is unavoidable, as in the construction of cheap, temporary buildings, wood that has been pressure-treated with an approved
preservative by a standard process, or that which is naturally resistant, should be req -uired. (See Federal Specifications on Dage 16.) It is an additional safeguard to install metal termite shields on top of such piers or posts so as to prevent termites from tubing up through season checks in the posts or piers and gaining access to the building.
Porches and Terraces
It is highly important that porches and terraces be effectively isolated from the building proper. The
floor or slab of such a porch or terrace nearly always joins the exterior wall or foundation of the building at a point above the level of the sill or the joists
that support the first floor. This condition usually provides tenaites with direct hidden access from the
Circular 2 Termites 14
soil or other fill material to the woodwork of the building and is responsible for most of the infestations in
buildings of this type.
Protection against such infestation can be provided
by the use of a properly designed and installed metal barrier or apron. It is immaterial whether the apron is installed over the top of the foundation wall (fig. 14) or attached to the outer side of it (fig. 15), before being extended to the top of the p--rch slab, just so long as the
apron effectively isolates the soil and slab from the woodwork of the building and makes an impervious barrier to termite attack through hidden points of entry. An important feature that should be embodied in all such aprons is a vertical extension beneath or behind the water table or trim to serve as a flashing to prevent moisture from reaching the sill and causing decay (fig. 16 A and B).
If '.he apron extends over the top of the foundation beneath the sill, it should be designed so that termites w ill not be provided with hidden access to the sill or adjacent woodwork at either end of the apron. One method of installation is to bring the masonry or concrete up to within 2 inches of the ultimate height of the foundation. Then along tile wall.back of the porch lay a course of bricks with joints well filled with mortar, on which to seat the metal. At each end of the course of bricks bend the metal down to the wall, then again parallel with it, so that the
outer 6 inches of the barrier can be covered with 2 inches of concrete to make the ends termite tight. Then the remainder of the wall is capped with poured concrete (figs* 17 and 18 A and B),
In situations where the porch or terrace is adjacent to a basement, the metal apron need be extended beyond the basement face of the foundation only sufficiently to allow for inspection* Where such inspections can not or will not be made, the metal should extend 2 inches horizontally and then downward for an additional 2 inches at a 45 degree angle so as to prevent termites from passing
underneath and around the apron to reach the sill or other adjacent woodwork*
Circular 2 Termite 15
~ 0 i S t
Eo rth fi IIco_-E
Figure 14. BREAD-PAN, OR THROUGH SHIELD
OVER WALL AND PORCH
a- J o i S
Figure 15. PATENTED SHIELD ON WALL AND PORCH
Circular 2 Termites 16
lJo ist .4 k . .
Figure 16 A- B WALL SECTION AND FRONT VIEW OF PORCH, SHOWING USE OF STRIP TYPE METAL APRON
Circular 2 Termites 17
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Cirmlar 2 Termites is
Wooden Porches or Steps
The lower or outer step and the platform supports should rest upon poured or solid concrete bases or aprons extending at least 6 inches above grade and sloped for drainage (fig. 10). If the sides of porches
are to be enclosed, the siding should be supported on a low concrete wall. Provision should be made for adequate ventilation and inspections through the side walls,
Door frames or jambs should not extend into or
through concrete floors that rest on soil. This is particularly true for garage doors or doors leading into
basements from outside stairways*
Outside fuel boxes should not be closer than
6 and preferably 12 inches from the building. If made of wood they should rest on concrete or masonry supports to avoid unnecessary damage by termites and decay.
Wooden ladders attached to buildings, such as army barracks, to serve as fire escapes should rest on concrete footings or be hung with a clearance of at least
6 inches above the soil,
Windows Below Grade
When windows or other openings below outside
grade are framed with wood the foundation wall surrounding the wood frame must be impervious to termites and the level of the areaway or well bottom should be at least
six inches below the lowest wood. This permits inspection,
Skirting Between Foundation Piers
Where pier foundations are used. it is sometimes desirable to close the spaces between piers so as to make
Circular 2 Termites 19
it easier to heat the buildings. If this skirting is made of wood or other material containing cellulose, and is in direct contact with the earth, it may be attacked by termites as well as furnish them access to the wood above, It is, therefore, necessary to provide a minimum clearance of 2 inches between the lower edge of the skirting and the earth and 1 inch between the sides of skirting and the Diers (fig. 19). If such clearance space is closed 'in during the winter it is very important that the space be reopened by early spring before termite activity is resumed.
Where permanent complete closing of the space between piers is required a low, poured concrete wall or beam between piers should be provided and inspected periodically for the presence of termite tubes. The skirting may then extend all the way down to this wall or beam and across the outside faces of the piers, providing it is kept at least 6 inches above grade at all points. Adequate ventilation is absolutely essential to avoid creating moist situations favorable for termites and decay. Ventilation should be proportioned on the basis of a minimum of 2 square feet of net opening for each 25 linear feet of wall (fig. 20),
Where openings for access, light or ventilation are framed with wood or other material containing cellulose, such frames should be kept above the low wall line to permit inspection, Jambs of these frames should
rest upon the wall and should not be extended into or below it*
Wood Used in Basements
Wood basement partitions should be placed after the concrete floor is poured. No door frames or other partition member should extend into or through the concrete floor. In large basement areas with concrete floor subject to cracking, it is important to prevent such
cracking directly under the woodwork by using reinforced concrete. Metal plates or concrete plinths used under wood posts, partitions, etc., will reduce the danger of termites gaining entrance to wood through cracks in the
floor and also will aid in preventing decay,
Circular 2- Termites 20
e e @e T I t 1
Figure 19. CLEARANCE OF SKIRTING AROUND SHIELD ON
PIER, AND GROUND CLEARANCE
....................... ... .. ........ .......
Figure 20. SKIRTING WITH VENTILATOR
BETWEEN PIERS, AND RESTING ON CONCRETE CURB
Cirmlar 2 Termites 21
Where basement rooms have finished or furred wall surfaces below the outside grade level, it is advisable to use pressure-treated wood or steel furring to avoid damage by termites and decay. Termites may be'provided with hidden access at form wires, spreader sticks, or cracks in the concrete wall, Expansion joints between the concrete floor and the wall should be filled with coal-tar pitch,
If wood floors are to be laid over concrete, they should be protected as described on page 15.
Girders, Sills or-loists below Grade
Avoid placing wooden girders, silis or joists
in or on foundation walls below the outside grade level, Cracks, form wires or spreader sticks may provide termites with hidden access to this wood, Decay will also be a serious problem under such conditions.
Water Pipes, eta,
All plumbing, electric conduits, etc., should be
clear of the ground and suspended from girders and joists, They should not be supported by wooden blocks,, stakes or partitions connecting with the ground, because of the danger or termites tunneling up to the joists, sills and floors.
Where concealed pipes or steel columns penetrate concrete ground slabs or foundation walls, the spaces
around tnem should be filled with coal-tar pitch.
The use of metal shields on pipes located where
soil moisture conditions are favorable for upward tubing is advisable in oases where such pipes penetrate the soil
directly and cannot be inspected (fig, 10)o
Concrete Platforms or Ground Slabs
Warehouses, garages, storage depots or similar
structures having cement floors on grade must have no wood
"R AIRY aft
Circular 2 Te,,altes 22
used below the level of the upper surface of the floor. The top of the foundation wall should extend at least
6 inches above the surface of the floor. If the f oundation is of unit masonry it should be capped with 2 inches of reinforced or 4 inches of plain concrete. Wood partitions should be placed after the floor slab has been poured and no door frames, studs, or partition member should extend into or through the concrete floor. No wood
plugs should be placed in these concrete floors for nailing.
When a wooden floor is to be laid over the cement floor or slab, the sleeper joists and flooring should be pressure-treated with an approved preservative to protect against decay and termites. The expansion joints in the floor as well as the joint between the cement floor and
the foundation wall should be filled either with coal-tar pitch or a crimped metal connector, or a cement sanitary cove should be used and extended up on the wall above the
surface of the wood floor (fig. 9).
Cement floors that are likely to crack should be
Use of Pressure-Treated and Naturally Resistant Woods
The use of treated wood in buildings has been mentioned under the discussions of foundation piers, flooring, sleepers on concrete slabs and furring for walls* Its use is rather specialized and it is primarily intended where protection from both decay and termites is involved or where wood must come in contact with the ground or be laid on concrete on the ground. For fence posts, poles, etc., ilt is especially recommended. Likewise certain termite resistant woods will give good service in
The length of service to be anticipated from
a given piece of chemically impregnated wood depends upon such factors as (1) the kind of preservative used, (2) the concentration, dosage and absorption, (3) the method of treatment, and (4) the conditions under which it is placed in service, In general, however, it may be said
Circular 2 Termites 23
that the longest life results from vacuum, pressurecylinder treatments, next from hot and cold open-tank treatments, and lastly from superficial brush, dipping or spray treatments. The latter seldom add more than
2 to 5 years to the life of any timber,
The following provisions concern the use of pressure-treated wood:
Timbers or lumber that must be used near
or in contact with the ground shall be thoroughly impregnated by a standard pressure
process with coal-tar creosote, with a retention of not less than 8 pounds per cubic foot of wood, or wf*th other approved equivalent preservative, o protect against damage by termites and decay. Timbers should be completely framed before treatment whenever possible, but when cutting after treatment is
unavoidable, the cut surfaces shall be given two coats of hot coal-tar creosote or other
Floor sleepers or joists embedded in, or
laid on masonry or concrete which is in contact with the ground, shall be impregnated
with an approved preservative in order to insure protection from decay and from termites that may reach the wood through cracks
in the concrete or masonry.
4/Under present Federal Specifications TT-W-571a, the Department of Agriculture recommends impregnation
with coal-tar creosote at the rate of 8 to 12 pounds per cubic foot for timbers to be used in contact with the ground; where timbers are to be used above ground and painted or finished, it recommends impregnation with
zinc chloride at the rate of 3/4 to 1 pound per cubic foot*
Circular 2 Termites 24
Where untreated wood must be used near or in contact with the ground, some protection may be had by using wood that is naturally resistant to termites, No woods are absolutely immune to termite attack, but the slow-growing heartwood of some species contains
sufficient chemical extractives to make it highly resistant. Sapwood is not resistant, Among those species that are commercially available are foundation grade Califomia redwood, all-heart southern tidewater red cypress, and lightwoodd" longleaf pine,
Use of Metal Termite Shields
To many people, termite protection simply means
the installation of metal shields on the foundation of a building. This conception is erroneous, for shielding is only one means of preventing termite infestation, Where buildings are well constructed as outlined above, most of those conditions which cause termite damage are
eliminated and shielding can be omitted without undue risk of attack (fig. 26).
As explained previously, upward tube building by termites is not very common on exposed surfaces of foundations except in humid enclosed areas and where the soil is moist. Consequently impervious piers or walls that are well ventilated offer adequate protection under
most conditions, particularly where the soil is kept dry. Furthermore, if inspection is provided the occasional tubes which are built up on the exposed faces of concrete or masonry can be broken off and the colony treated with poison. (See pages 24to 28) Termite protection, therefore, is mainly a matter of sou7ff-construction,
Where it is desired to use every possible means
of avoiding infestation by termites or where it is impossible to comply with the foregoing recommendations as, to structural rpquirementsl it may be desirable to use shields as an additional precaution* Their use should not, however be regarded as an excuse for accepting or allowing poor construction*
Circula&r 2 %=uit** 25
The use of shields that are properly designed
and installed will result in giving as nearly complete protection as can be obtained with present known methods, providing they are used as a supplement to good construction and not as a substitute for it. Many cases have been observed where shields were installed on foundations at points where there was little danger of termites attempting to gain entrance to the building while the points of greatest danger, such as filled porches and terraces, were left unprotected. Recent
experience has shown that much shielding has been poorly designed and incorrectly installed, resulting in giving the owner a false sense of security. Even when properly installed, shields give protection only during the period that the metal lasts and the joints and means of anchorage are termite tight. The importance of correct design and installation and =subsequent inspections ,can not be over-emphasized.
In general, metal shields are recommended under the following conditions:
(1) Where unit masonry foundations are not
capped with 2 inches of reinforced or
4 inches of plain concrete.
(2) Where impervious foundations are used
but where moist soil conditions exist
because of inadequate clearance, drainage and ventilation beneath the building (See page 8). This applies particularly to certain restricted localities where high humidity and moist soils full
of organic material produce extremely
hazardous termite conditions.
Several types of shields are available for use on foundation walls. The type best suited for any particular building will depend upon the nature of the foundation.
The Brtadpan Tyeof Shield
The breadpan type of shield is especially suitable for use over masonry walls or piers of unit type (stone, tile, brick, or hollow blocks) not properly capped
Circular 2 Termites 26
with 2 inches of reinforced or 4 inches of plain concrete, to prevent termites from working througji such units and reaching t1le foundation timbers. The following describes their proper installation:
1. On interior walls and on To isolate
interior walls and piers within unexcavated areas, extend the metal entirely across the top of the wall or pier beneath the sill and beyond it to project on each side 2 inches horizontally with an additional 2 inches projecting downward at a 4'5 degree angle.
2. On exterior foundation walls and piers. On
exterior foundation walls, the horizontal projection beyond the outer face of the wall may be omitted where it is objectionable on account of appearance, as the wall is exposed and any termite activity can be readily detected, However, sufficient metal should extend beyond the wall to allow a slight projection downward to act effectively as a moisture proof flashing, and be readily inspected (fig. 12). On the interior side of these walls, full projection should be provided, the same as for interior walls and piers, when inspections are impossible or impractical. In all breadpan shielding work, the shield should be bedded on fresh cement mortar or coaltar pitch to seal any voids made around anchor bolts where they pierce the metal barrier,
When the spaces between exterior piers are closed with skirting or lattice work a minimum clearance of 2 inches must be Drovided around the edge of the shield
and 1 inch between the sides of the skirting and the piers (fig. 19).
The Strip Type of Shield
The strip shield is embedded in, or attached
to, the side of the wall in such a manner as to fom an impervious and permanent joint or union between the metal and wall. It is particularly adaptable for use on poured concrete walls (fig. 21) but may be used on properly capped unit type foundations, whether hollow or solid (fig. 22).
One type of such shield consists of a sheet of
Circular 2 Termites 27
Figure 21. STRIP TYPE SHIELD OVER WALL Figure 22. STRIP TYPE SH IELD
AN D METAL APRON OVER WALL AND PORCH
Circular 2 ?ernites 28
metal 8 inches wide which is embedded near the top of
the foundation wall. The wall must be leveled with fresh mortar before putting the shield in place. The
strip should extend over the wall for a distance of 4. inches in order that it may be properly anchored. To do this, rust-proof nails snouli be placed about 1 inch from the inserted edge at every 3 or 4 foot interval along the strip. The wall must then be capped with 2 inches of reinforced or 4 inches of plain concrete. This leaves exposed a horizontal projection of 2 inches with an additional 2 inches at a 45 degree angle.
Other shields of this general type have been
developed by private inciustry; many of them are patented. Most or them are rirmly inserted. or attached by screws or nails to lead plugs embedded into impervious foundation walls and then further sealed by means of dense concrete or coal-tar pitch (figs. 23 and 24). Those which are designed so as to meet the same entomological requirements as fulfilled by the breadpan type of shield, as previously described, and are correctly installed in or
on impervious walls, should be equally as effective,
Additional R~equirements for Installing Metal
In addition to the requirements mentioned
above under each type of barrier, the following apply:
where the barrier is made or copper, "cornice temper"t hardness should be specified and it should preferably not be lighter than 16 oze to the square foot. Where other metals are used, not less than 26 gauge should be specified. Under moist conditions ordinary galvanized iron will not last more than 5 to 10 years. Copperbearing galvanized iron is reported to last somewhat longer.
All angles and breaks should be formed on a
metal brakce machine or stamped, and hand bending should not be permitted. The connections between shield lengths or widths should be looked, riveted and soldered or otherwise fastened with termite-proof joints to take up expansion and contraction stresses.*
Circular 2 ?ermites 29
Figure 23. PATENTED SHIELD ON WALL
f ~~Detai I -oI a
-'----T -" -- ,
Grade LE pdstic
Figure 24. PATENTED SHIELD
Circular 2 Termites 30
All corners and intersections should have the metal properly joined and the projecting angles properly extended without gaps,
Steel I-beams or girders inserted in the wall below grade or below the shield line, must be boxed or
otherwise protected so that the continuity of the shield is not broken*
Where shielding levels change, as at differences in outside grade lines, a vertical section or apron connecting the lower and higher shield levels should be installed,
Periodic inspections for evidence of termite attack should be made of all buildings in sections of the country where termites are known to be a hazard. This is simply a matter of good insurance and should be insisted upon regardless of how completely preventive measures have been employed in construction* The frequency at which such inspections are needed will depend upon the abundance of termites in the area and the type of construction involved* In no instance should more than 12 months pass between inspections. If termites are found to be attacking a building, control measures as described in the following section should be employed.
CONTROL OF INFESTATION BY TMMITES
Once a termite infestation has been discovered in the framing timbers or other parts of a building, prompt steps should be taken to control it (fig. 25). Each year the number of termites increases and the damage caused by them continues at a progressively faster rate*
In control, the same principles apply as when
building to prevent infestation* That is, the passage of the workers f rom the moist earth to woodwork of the building must be broken. To do this all wooden parts of the building must be insulated from the ground, proper
ventilation within the foundation must be provided, and wood debris must be removed from beneath and adjacent to
Circular 2- Termites 31
the building. The first important step is to locate the
place of termite entry. Most frequently this will be
found around the porches or through hidden points of access in the foundation. The second step is to destroy
existing shelter tubes and cut off the passageway between
the termites' subterranean colony and the infested units of the building. This latter step usually means cutting
off their moisture supply so that those termites remaining in the wood will dry up and die. when present in
large numbers, however, they will attempt to build shelter
tubes down to the earth after their original passage or
passages are blocked. periodic inspections for a few days will be necessary in order to break off such new tubes to
prevent their reestablishing contact with the soil moisture.
A third step may be advisable in basementless areas. That
is to find and destroy any wood present in the soil near walls where tubes are being constructed upward over concrete or masonry to the framing above. This should be
followed by soil treatments as described below.
Pigro 25. Termite tubes being extended from wood framing down to soil for
*etablishing moisture contacts, also upward on the pier at left.
Circular 2- Termites 32
..- :. T 2" reinforced concrete cop
Grode E 4" ploin concrete cop
Figure 26. CAPPED MASONRY WALL
Circular 2 TernitmB 33
Several methods may be used to control termites
and the particular one or ones selected depends entirely upon the situation at hand. Such factors as the following must be kept in mind:
1, The value of the building,
2, The importance of the building from
a use standpoint and length of service intended,
3. The money available for control work,
The availability of the necessary materials.
The following methods of control will be discussed and the value of each considered: structural measures, including the use of concrete, masonry and metal barriers; soil poisons; treated wood, and termite resistant woods,
Primary or Structural Control Methods
Mechanical Blocking with Concrete or Masonry
The maximum and most lasting protection is obtained by mechanically blocking the termites from entering the building. often the removal of wood from contact with the ground is sufficient. At other times voids in concrete, due to the settling and cracking of walls or expansion joints, have to be filled with a dense mortar or with coal-tar pitch, Timbers may have to be replaced, soil removed or poisoned, areas ventilated, and even metal barriers in the form or shields or aprons installed. Such changes aid in improving the building by increasing its value and in lengthening the period of serviceability. The details relative to structural changes have been discussed under the preceding section.
Mechanical Blocking with Metal Aprons or Shields
Under conditions where buildings have not been constructed in accordance with the requirements as set
forth under the preceding section and infestations have occurred, protection may be had by the use of metal barriers in the form of aprons or snields. In many instances
Circular 2 Tornites 34
however, as previously mentioned, structural changes involving the use of plain concrete alone to insulate all wood from ground contacts, may be sufficient to control
the termites and make the installation of metal barriers unnecessary. However, when large colonies have developed there is much more danger of upward tubing over reconstructed walls, and shields or soil poisons are additional safeguards,
Where metal aprons or shields are properly designed and correctly installed, protection will be had by the, elimination of all hidden points of access. That is, where termites succeed in.penetrating masonry foundation walls, they will either be checked or forced out into the open and exposed when they reach the metal guard* Careless installations result in failures and give a false sense of security, Such also represent a waste of time and money.
The installation of a metal apron or shield in an infested building requires considerably more time and expense than in the case of new construction, as frequently considerable shoring up of the building is necessary before the damaged structural members can be removed or
portions of walls or piers taken down and prepared for receiving the metal barrier. In more simple cases, however, just removing a damaged sill. and replacing it with sound material or concrete will allow ample room for the installation of a breadpan or strip type of guard. In still other instances, where unit type masonry (stone,
brick, tile or hollow blocks) is concerned, the removal of the top layer of the foundation material may make it
Jble to install the metal. If taken out in 3 to 4
foot sections, jacking up the building may be unnecessary. Once the foundation or portion thereof that needs protection is prepared for the metal barrier, it should be formed and carefully installed, as mentioned under the section on shielding (pages 10 and 17 to 21).
Where it is impractical to employ structural methods alone to check termite activity, treatment with chemicals to poison the soil about walls, piers, and pipes can be used advantageously in conjunction with such methods,
Circular 2 Termites 35
or occasionally in place of them. Chemical treatments
lack permanent value, however, and should not be considered as equivalent to proper structural methods, Satisfactory control in buildings cannot be expected
under conditions where the chemicals are applied to or about wood that is left in contact with the ground, and decay is still possible.
Tests in the use of many chemicals as soil poisons have shown that when properly applied certain of them may be expected to give protection over a period of at least 5 years, The period of protection, however, is dependent to a large extent upon variable factors,
such as the nature of the chemical or mixture, the manner of application, the texture of the soil, the level
of the water table in the soil, the movement of subsurface drainage, and the exposure of the treated soil to the weather.
Some of the more promising chemicals include the
arsenicals, chlorinated naphthalenes, chlorinated phenols, coal-tar creosotes, and chlorinated benzenes. They are used alone or in combination,
Most authorities agree that applications of chemicals in the form of fumigants and sprays, even when applied under pressure, are ineffective for the control of subterranean termites. Successful treatments require that the ground be saturated for a considerable depth
around the foundation walls and piers of a building adjacent to possible points of termite entry. Some chemicals are poor penetrants and must be used in heavier dosages than others to be most effective#
Precautions to Avoid Injury to Animals and Plants
The above mentioned chemicals are toxic to plant life. Where valuable shrubs or flowers are nearby (1 to 3 feet) and where it is not desirable to temporarily remove them, protection may be had by lining that side of the trench next to the shrubbery with tar paper, paraffined canvas, or copper coated kraft paper. The latter is preferable where orthodichlorobenzene is used as it has a tendency to dissolve coal-tar products. Shrubs should be kept at a sufficient distance from the wall to permit inspections
Circular 2 Termites 36
of the exterior foundation and to allow the air to circulate freely beneath the building.
Care should be taken by the workmen to avoid letting the chemicals come in contact with the body, especially the eyes. It would be advisable to use chemically resistant (rubberized fabric or Neoprene-treated) gloves and a mask in closed spaces and to provide for adequate ventilation,
In the use of these chemicals care should also be taken to prevent contamination of wells or springs by seepage,
Methods of Application
Exposed foundation. When poisons are to be
applied to the soil adjacent to exterior foundation walls having deep footings, as along a full basement excavation, it is well to dig a trench the width of a shovel to a depth of 30 inches, as such a trench aids penetration of
the chemical. As the earth is replaced, apply the chemical at about 6-inch intervals. It may be necessary to vary this interval, depending upon the type and moisture content of the soil and the nature of the chemical being applied and quantity used.
When the poisons are used around foundations having shallow footings, as under basementless areas, a trench only a few inches deep is sufficient.
'Where a soil poison is used, such as a mixture composed of 1 part coal-tar creosote and 3 parts light fuel oil, or a 10 percent water solution of sodium arsenite, it should be applied along the exterior foundation trench at the rate of 4 gallons per each 10 linear feet (to treat approximately 25 cubic feet of soil) in the
case of deep footings, and at half that rate in the case of shallow ones to treat from 10 to 12 cubic feet of soil, Treatment of the soil within foundations in basementless areas should be at the latter rate if shallow footings are present,
Where a chemical having fumigating properties is used, like orthodichlorobenzene, lighter applications
Ctrodar 2 Teraltes 3T
will suffice, such as 2 gallons per 10 linear feet of trench to treat deep footings and 1 gallon to treat shallow ones, Where trenching is impractical, satisfactory.results may likewise be obtained in treating the soil over deep footings, by pouring this chemical into 2 inch diameter crowbar holes made 30 inches deep and spaced 15 inches apart* For this method of application, the same dosage should be used as for trenching about deep footings, In addition, it is-well to saturate the entire top layer of soil to insure a continuous treatment near the surface along the foundation wall. Where walls, piers, and floors are porous, they may have to be drilled and flooded with the toxic material to treat them adequately,
Enclosed, filled or unfilled porches, The treatment of enclosed, filled 3r unfilled porches requires a different procedure than is used in the treatment of exposed walls. To treat and maintain an enclosed unfilled poured concrete or unit masonry porch, it is necessary to make an opening in the wall at each end so that the interior can be inspected, any form boards or other wood present can be removed, existing termite tubes can be destroyed, and the area can be permanently ventilated. In the case of masonry walls, if there is a full basement opposite the porch, a 30-inch trench should be dug along the exterior foundation within the enclosed space to aid the chemical to penetrate near the footing. Otherwise, as when a basementless area-exists opposite the porch, a shallow trench all
around the enclosure will be sufficient, In the case of'poured concrete walls, a shallow trench is ample regardless of the basement construction, unless a crevice in the concrete has developed and extends to-near the footing,
To treat a dirt-filled porch or other similar area, lasting protection will be had by inserting a metal apron as described on page 10. Where a masonry foundation is concerned protection may also be obtained by making suitable openings in the sides of the porch wall and excavating the soil to the footing. Then the exterior surface of the foundation wall should be well cleaned and faced with concrete at least one inch thick, If such procedure is impractical,, a poison can be applied
Circular 2 Termites 39
to the remaining soil adjacent to the foundation after the filled earth has been removed down to about 6 inches below the outside grade. In some types of construction,
where the slab is not well attached to the main wall, it may be necessary to install a supporting wall or piers in order to prevent the concrete or masonry slab above
Ground slabs of concrete or masonry Here again the problem is somewhat similar to filled
porch, except the space between the slab and ground is lacking as the concrete or masonry frequently rests on grade level. Where it is impractical to install a metal or concrete apron, as mentioned above, then poison the earth below the slab with a suitable toxic material after all debris and tubes have been removed and destroyed. If the main foundation wall is of masonry, it may be more convenient to apply the chemical from the basement than to excavate beneath the slab from outside. In such case,
the removal of 2 to 3 feet of masonry wall, parallel with and slightly below the lower inner edge of the slab, would be possible without shoring it up, Through this opening the soil could be removed along the wall to provide a tunnel for inspection purposes and to apply the chemical. If the outside concrete or masonry slab is quite long, 2 or possibly 3 such openings in the foundation may be necessary in order to treat the soil effectively. unly one of them should be opened at a time so as to avoid the possibility of weakening the structure. Une such opening should be left for future inspection,
ahere the wall is of poured concrete, it is usually easier to apply the soil poison from the outside than
to attempt to bore through the solid wall from the basement. This would mean excavating the earth along the foundation wall from one or both sides of the slab, removing
any debris present, and applying the chemical to the shallow trench. As in the case of porches, it may also be
necessary to install a wall or piers to reinforce the slab above to prevent cracking
Circular 2 .rnitos 39
LIST OF COMPANIES HANDLING CHEMICALS
AND PRESSURE TREATED WOOD
The accompanying list of concerns and their products is included for the information of the users of this circular, without given or inferred guarantee of the reliability of the firms or endorsement of their individual products. No attempt has been made to make the list fully complete and no discrimination is intended or implied against firms whose names or products are not listed.
Capitol Chemical Company, 1050 30th Street, N. W.
Washington, D). C.
Dow Chemical Company, Midland, michigan E. I. duPont de Nemours & Company, Inc., Wilmington,
Electro Bleaching Gas Company, 9 East 41st Street,
New York City
James Good Inc,, Susquehanna Ave. & Martha Street,
Hooker Electrochemical Company, 60.East 42nd Street,
New York City
Hughes Chemical Company, 1424 Philpot Street, Baltimore,
Mallinckrodt Chemical Works, 3600 No. Second Street,
St. Louis, Missouri
Marshall Chemical Company, Marshall, Virginia Monsanto Chemical 4vorks, 1700 So. Second Street,
St. Louis, Missouri
Niagara Alkali Company, 9 East 41st Street, New York City Uleum Chemical Company, Scranton, Pennsylvania Solvay Sales Corp., 40 Rector Street, New York City
Coal-tar Creosote (Most paint and hardware stores)
Barrett Company, 40 Rector Street, New York City Bermuth Lembcke Company, 420 Lexington Avenue, N~ew York City Creosote Sales Corp., Lexington Buildiing, Baltimore,
Koppers Company, Tar & Chemical Division, Pittsburgh,
Circular 2- Termites 40
Li t e'uel Oil Of Kerosene Grade
Most oil refineries and distributors
American Anode, Inc., 60 Cherry Street, Akron, Ohio
Atlantic Creosoting Company, savannah, Georgia keystone Wood preserving Company, Philadelphia,
Taylor-uolquitt Company, 6partanburg, bouth Carolina
Chromated Zinc Chloride and Zinc Chloride
Atlantic Creosoting Company, Savannah, Georgia J. H. Baxter & Company, 333 Montgomery Street,
San Francisco, ualirornia
Taylor-uolquitt Company, Spartanburg, South Carolina nest Coast Wood Preserving Company, 1118 4th Avenue,
American Creosoting Company, Louisville, .entucky American Lumber and Treating Company, Chicago, Illinois
Plants: Elizabeth, New Jersey Franklyn, Virginia
Gainesville, Georgia Crossett, Arkansas
vveed, California Wauna, uregon
Atlantic Creosoting Company, savannah, Georgia
Eppinger & Russel Company
Plants: Long Island City, New York Jacksonville,
Forest Products Treating Company, 824 Pittock Block,
Plants: Dales, Oregon Laramie, Wyoming
Gulfport Creosoting Company, Gulfport, &ississippi J. H. Baxter & Company, 333 Montgomery Street,
oan Francisco, California
Norfolk Creosoting Company, 90 West street, P. U. Box 28,
Circular 2- Termites 41
Coal-tar Creosote (Cont'd)
Taylor-Colquitt Company, Spartanburg, South Carolina Republic Creosoting Company, 1607 Merchants Bank
Building, Indianapolis, Indiana
Plants: Indianapolis, Indiana Mobile, Alabama
West Coast Wood Preserving Company, 1118 4th Avenue,
American Lumber and Treating Company, Chicago, Illinois
Plants: Elizabeth, New Jersey Franklyn, Virginia
Gainesville, Georgia Crossett, Arkansas
Weed, California Wauna, Oregon
Zinc Meta Arsenite (ZMA)
Eppinger & Russel Company
Plants: Long Island City, New York Jacksonville, Florida
r eystone Nood ?reserving Company, Thiladelphia,
Norfolk Creosoting Company, 90 West Street, P. 0. Box 28,
% 2 Termites 42
LIST OF PUBLICATIONS ON TEMIITES
AND THEIR CONTROL
Snyder, T. E. ------- 1935 -- Our Enemy the Termite.
Company, Ithaca, New York
Kofoid, Light, etc. -- 1935 Termites and Termite Control. University of California Press, Berkeley, California
McCauley, W. E., and Flint, W. P. --------- 1940 Outwitting Termites in
Natural history survey Circular 37, Urbana, Illinois
Turner, v'eely and Townsend, James F. --- 1939 control of Termites in Buildings. Uonnecticut Agricultural Experiment Station Circular 134, ivew haven, Connecticut.
Turner, Neely and Zappe, I. e. --------- 1938 Case studies in Termite
Control. 37th Report of the State Entomologist, Bulletin 408,
pp. 208-217, Connecticut Agricultural Experiment Station, i.ew Haven, Connecticut.
Snyder, T. E. -------- 1939 preventing Damage by Termites or ivhite -Ants. u. 6. Department of
Agriculture farmers' Bulletin 1472, washington, ). C.
Circular 2- Termites 143
baerg, q. J. --------- 1940 -- Termite Damage: ereventives and Remedies. University of Arkansas College of Agriculture, Agricultural Experiment Station, uletin No. 385, Layetteville, Arkansas.
Hodgkiss, H. z. ------ 1937 -- termite Control for Pennsylvania. The Penn state college, Division of Agricultural Extension Circular 187, %tate College, vennsylvania
Davis, J.J. --------- 1937 -- The Prevention and Control
of Termites. Purdue University Extension Bulletin Ivo. 225, Lafayette, indiana.
Federal housing Administration ------ 1939 -- Protection Against Termites.
Technical Circular No. 2 Federal nousing Administration, vvasnhington, D. C.
UNIVERSITY OF FLORIDA 3 1262 09314 9978