A x'J.V.NMblfD 1C83KSTACKS- I0DCUMENTS UNITED STATES DEPARTMENT OF AGRICULTURE Forest Service Division of Forest Insect Research Forest Insect Laboratory, Beltsville, Maryland RECOMMENDATIONS FOR PROTECTING WOOD IN NEW CONSTRUCTION FROM ATTACK BY SUBTERRANEAN TERMITES Protection from subterranean termite attack and subsequent damage, can be had by adopting the following structural measures and by treating the soil during construction of a building. These measures concern the elimination of wood (the termite's food) from the ground, the adoption of sound construction practices, and the application of soil chemicals to keep termites away from the foundations of the buildings. I. STRUCTURAL MEASURES The degree of success obtained in protecting wood and other cellulose- containing products used in new construction, from attack by subterranean termites, will depend largely upon the thoroughness with which the following provisions are enforced: 1. Eliminate all wood from the ground . Remove all stumps and wood debris from the building site before construction begins. During construction make certain all grade stakes, spreader sticks and form boards are removed from concrete before it sets. , Se^ that all wood supports (stair carriages, door jambs, etc.) are placed on top of concrete - not set in it or extend through it. Do not allow holes to be drilled through the concrete floor and wood pegs inserted to which the base-plate for partitions are frequently nailed, as termites may find them and enter. Do not allow wood debris to be included in the soil about the foundation when the final grade is being established, especially about the foundation entrance platform. 2. Eliminate voids in mortar joints in unit masonry walls and piers . Voids left in mortar joints of unit masonry walls invite termite entry and subsequent damage to wood. The mortar joints should be well pointed up along the exterior of the entire foundation wall. This is particularly important below grade and at other places higher up, such as where the concrete slabs join the wall, and where porches and sun parlors occur. A moisture-proof coating to the exterior surface of the foundation will give added protection from dampness and termites. 3. Use pressure-impregnated lumber on concrete slabs in contact with the ground . Where untreated wood floors are to be laid over concrete floors, pressure-impregnated lumber should be used for nailing strips and sub¬ flooring (See Federal Specifications TT-W-571 C ). Expansion joints in the concrete floor and between the floor and the foundation wall should be sealed either with hot coal-tar pitch, or with a rubberoid bituminous material, whether wood or other types of flooring materials are to be used, as termites frequently enter at such places. 4. Provide for adequate clearance in crawl space s. There should be a minimum of 18 inches below the bottom of all wood floor joists and 12 inches beneath girders and beams to allow sufficient space for making inspections. Such space also serves to keep termites from tubing directly upward from ground to wood, and aids in keeping down condensation moisture and subsequent decay. In areas where high water tables persist, condensation moisture can be kept down by laying smooth-surfaced roll roofing paper, weighing 55 pounds or more per roll of 108 square feet, or its equivalent, over the surface of the soil. In such instances the crawl space ventilators, or most of them, can be safely closed during the winter. 5. Provide for adequate cross ve ntilation in crawl spac es. In crawl spaces of buildings where soil covers (roll roofing paper) are not used, adequate cross ventilation is important in preventing excess moisture from forming. Moisture content of the wood in excess of 20 per¬ cent, is conducive to decay and termite damage. In general, the net free area of ventilation opening should be equivalent to 1/160 of the ground area beneath a building. 6. Pr ovide for adequate drainag e. Good drainage, like adequate ventilation and clearance of wood • « » to ground, is necessary to prevent a build-up of moisture in the soil and on the understructure of the building. II. SOIL TREATING WITH CHEMICALS Soil chemicals have demonstrated their effectiveness and reliability in safeguarding wood in buildings from termite attack for a period of about 10 years, according to the results obtained from tests conducted by the Forest Service. On the basis of present information, it appears likely that even longer periods of protection can be anticipated when the chemicals are properly applied about the foundation walls, piers, and the surface of soil that is to be covered with concrete slabs. The latter may serve as floors, entrances to buildings, patios, terraces, or walks. 2 w 1. Chemicals and Concentrations . A number of the chemicals —/ have been tested and the following are recommended for use in treating the soil about the foundation of buildings: %j Aldrin . To be used at a concentration of 0.5 percent, applied in oil solution or water emulsion. —' Benzene hexachloride (Technical ). To be used at a concentration of 0.8 percent gamma isomer, applied in an oil solution or water emulsion. Chlordane . To be used at a concentration of 1.0 percent, applied in an oil solution or water emulsion. Dieldrin. To be used at a concentration of 0.5 percent, applied in oil solutions or water emulsions. DDT . To be used at a concentration of 8.0 percent in oil solution. 2. Rates of application for: (1) Slab-on-Ground Type of Construction Apply 1 gallon per each 10 square feet of soil surface (before the gravel fill has been added) as an over-all treatment prior to pouring the slab which may serve as a floor, attached porch, terrace or an entrance platform. Where the gravel or cinder fill has been applied at the time of treatment, increase the application to 1% gallons per 10 square feet. Unless the treated soil or fill is to be promptly covered with a vapor barrier, or by the slab, precautions must be taken to prevent disturbance of the treatment by humans or animals. A number of chemicals formerly recommended have been excluded from the list, either because of high cost, high toxicity to plants and animals, shorter periods of effectiveness, or other undesirable characteristics. Soil chemicals should not be used about foundations of buildings where wells are used for drinking water. There is danger of the chemical reaching the water by means of subsurface drainage. 3/ Emulsions properly applied are relatively non-toxic to the roots of shrubs and trees. Oils may cause some burning. Therefore, its use is restricted to the interior of buildings. Oils no heavier than No. 2 Fuel Oil should be used. 3 In critical areas, where termites are frequently found entering floors, such as at the expansion joints and around utility entrances in the slab (openings left for the insertion of pipes, conduits, sunken heaters, etc.) apply the soil chemical to these areas at the rate of 2 gallons per 5 lineal feet. Along the exterior of the foundation wall, also apply the emulsion at the same rate. (2) Crawl-Space Houses, or Crawl Space Portions of Houses with a Partial Basement . Apply 2 gallons of the emulsion per 5 lineal feet of wall, to the critical areas under the house, such as along the inside of the foundation walls, and around piers and utility entrances. (Do not make an overall treatment here, otherwise, humans or animals crawling through the treated soil, might come in contact with the toxic chemical and possibly experience some irritation). When treating along the exterior of the foundation walls, including the part opposite entrance platforms, porches, etc., apply the emulsion at the rate of 2 gallons per 5 lineal feet per foot of depth from finished grade to top of footing. Apply 1 gallon per 10 square feet of ground surface as an over-all treatment, only where the attached porches, entrance platforms, utility entrances, etc., have a covering slab of concrete on fill or ground. (3) Easement Houses The application here will be the same as mentioned above for the crawl-space houses. (4) Voids of Unit Masonry Walls All voids of unit masonry walls and piers (spaces other than mortar joints) are to be treated with the chemical at the rate of 1 gallon per 5 lineal feet and applied from the grade to the footing. Behind filled porches and entrances to buildings, the wall voids should be treated to the top level of the concrete slabs. 3• Application Techniques (1) Shallow Footings Where the footing of the foundation wall is within 2 feet of the surface, as is often the case with buildings having crawl spaces, or with ranch style construction with concrete slabs on the ground, a shallow trench is sufficient to give effective distribution of the chemical when applied at the rates indicated. A shallow trench is pre¬ pared along the exterior foundation wall by removing the earth from the wall for a width of 1 foot and a depth of about 15 inches. In no case should the treatment be extended below the top of the footing. Along the interior *7all, in a crawl space, the trench will be of the same width, - 4 - but usually it is sufficient to make it only a few inches deep. This is the case where the soil is loose or is sandy. In the case of a compact heavy clay soil or shale, it should be dug as deep as mentioned for the trench along the exterior wall. (2) Deep Footings Where the footing is in excess of 2 feet in the ground, as is the case where there is a basement, the trench is made 15 inches deep, with 1-inch holes a foot apart along the bottom of the trench, for an additional depth, until it reaches the top of the footing. A portion of the chemical should be poured in the bottom of the trench and about six inches of soil should be added, then more chemical is applied. This is repeated until all of the soil and chemical have been utilized. By estimating the number of applications to be made, one will know then how much of the total quantity to apply each time, so as to distribute it evenly from the bottom of the trench to the grade. Treatments should not be made (1) when the soil, or fill, is excessively wet, or (2) directly following rains, or when the ground is frozen, as in such instances, it will not penetrate to the desired depth and some of the chemical may be lost through surface runoff, leaving an inadequate concentration in the soil to insure giving long residual protection. 4. Toxicity and Precautions. All of the chemicals mentioned above are somewhat toxic to humans. Avoid spilling it on the body as it is apt to be absorbed by the skin. If it does contact the body, wash off the chemical with warm soapy water. If it reaches one's eyes, wash with boric acid water ( 1 teaspoon per glassful of warm water, or with plenty of water, and call a doctor if necessary). All but the emulsions are toxic to plant life. In the oil phase, they can cause localized burning like any other oil-borne chemical. Soil chemicals should not be applied in the vicinity of wells used for drinking purposes. Children and pets should not be allowed to play in the treated soil . Revised January 1959 5 ^ I • - * 1