A shorter version of the article was published in the Journal of School Business Management.
“Prevention is the key to effective, least-hazardous pest management programs in schools,” advises the Department of Pesticide Regulation (DPR) Director, Mary-Ann Warmerdam.
“If the conditions that attract and support pests-the presence of food, water, shelter, and access-are not eliminated, then other management practices are likely to fail. Everyone involved in the planning, design, construction, remodeling or retrofit of school buildings should be aware of the need for long-term prevention or suppression of pest problems,” said Director Warmerdam. “Pest prevention will reduce overall costs of pest control operations, as well as other maintenance and operating expenses.”
A thoroughly integrated approach to pest management in school buildings begins in the early planning stage. Too often pest management is not considered at this point. The way a building is put together�including materials, construction techniques, and attention to detail-will impact future pest prevention efforts throughout the life of the building. Considering pest management needs during design, development and construction means to incorporating features that will exclude pests, minimize pest habitat, and promote proper sanitation.
Several basic structural features cause most problems. Many buildings have pest exclusion problems at doorways and windows. Heating, air conditioning, plumbing, electrical service, and fire sprinklers provide other pest entry points. Even in new buildings, electrical conduit, water and gas lines, and communication cables generally have large openings that permit pest entry. Wall cavities, ceiling cavities, and the space beneath floors can all provide pest shelter. From these areas, pests generally have ready access to the rest of a building. Utilities, overhead suspended ceilings, and air conditioning ducts provide a very effective pest distribution system.
Although pest-resistant building practices most commonly reduce shelter and access, they can also reduce food and moisture sources through proper sanitation, reducing trapped moisture, and improving drainage.
While proper construction practices are the emphasis here, they cannot stand alone. A strong, preventive maintenance program is essential. Poor sanitation or leaving entryways open will make even the best-designed and constructed building susceptible to pest problems. Using the practices discussed below, together with routine inspection and awareness of potential pest problems, can greatly reduce or eliminate the potential for infestations, especially when followed by responsible maintenance.
(For online information about pest prevention and maintenance, go to www.cdpr.ca.gov/schoolipm/, and click on “Managing Pests” on the left side of the page. Click on “Pest Prevention and Management,” then “Pest Prevention-Maintenance Practices and Facility Design.”)
The following guidelines and practices illustrate the variety of practices that can be used and their value in pest prevention. No single practice will work equally well in all circumstances. Certain practices listed below may not be appropriate where structural requirements or budget considerations preclude them. Once the basic principles are understood, there is no substitute for resourcefulness and ingenuity in developing practical, site-specific solutions. Sources listed in the Reference section offer many additional suggestions.
- Eliminate gaps or flaws in foundations and slabs, or where the wall framing meets the foundation or slab floor. These openings may be large enough to allow insect or rodent entry. Older buildings commonly have cracked foundations, cracked plaster or mortar, warped siding, or broken and torn vent screens that allow pest entry.
- Install physical barriers beneath joints or other discontinuities in the foundation. No hidden cold joint should exist in the foundation unless there is a physical barrier. A sheet metal barrier to termites can be installed from below the wall sill plate or first block course horizontally to embed in a mortar joint.
- Include the design of footings for brick, stone, or other veneers with the other pre-construction foundation planning. A concrete bearing ledge that is poured integrally with the concrete foundation should support these heavy veneers. If poured as part of the foundation, the ledge prevents termite entry into the building between the footing and the foundation.
- Use a sand barrier. Use a 3-inch layer of sand underneath slab construction. Use 1-3 millimeter particle size in place of unsifted sand to provide a permanent termite barrier (western subterranean and Formosan termites). This will prevent termites from penetrating cracks in slab construction.
- Use naturally durable wood http://www.mcvicker.com/twd/gwdi97/page000.htm or non-wood materials. The only sure prevention of termite problems is the use of building materials other than wood.
- Eliminate all wood-to-soil contact. Soil should always be from 6 to 18 inches below any wood member – the greater the distance, the better.
- Extend foundation below ground. Good foundations will normally stop rodents from getting into buildings; however, if foundations do not rest on bedrock, they should extend vertically below ground at least 3 feet or have an L-shaped curtain wall about 2 feet deep with a 1-foot projection from the building. On piled foundations, the reinforced concrete beam spanning the piles should extend 3 feet below ground to stop rodents.
- Modify foundations on older buildings with concrete or metal barriers to stop rodents from digging their way in.
- Check foundation vents to make sure they are tight and appropriately screened (�-inch hardware cloth to exclude rodents).
- Avoid burying or storing cellulose-containing material (wood scraps, form boards, vegetation, stumps, large dead roots, cardboard, trash, and foreign material) near the structure. To reduce chances of termite infestation, no cellulose-containing material should be buried on the building lot within fifteen feet of any building or the position of any building proposed to be built. Cellulose materials are attractive food sources for termites that can then move into the structure.
- Prior to concrete placement, remove all cellulose-containing material from the area encompassed by the foundation and the area within one foot of its perimeter. The fill material should be free of vegetation and foreign material. .
- Prior to concrete placement, clean all cellulose-containing material from cells and cavities in masonry units, and from air gaps between brick, stone, or masonry veneers and the structure.
- After all foundation work is completed, remove all loose wood and debris from the crawl space and within one foot of the perimeter of the building. All wood forms and supports should be completely removed.
- Eliminate sources of chronic moisture in and around the structure. This is one of the most important requirements for successfully managing subterranean termites, carpenter ants, and some wood boring beetles. Good drainage design will help to prevent moisture buildup in and around the structure.
- Use moisture barriers. In above-ground foundations, moisture barrier films such as 6 mil polyethylene can be used to cover the area under the structure. This will help decrease moisture buildup in sub-flooring. Some builders recommend the use of moisture barriers under slab foundations as well.
- Slope all exterior grades away from the structure to provide drainage.
- Construct and seal all adjoining components such as porches and planter boxes to prevent moisture and soil contact with the structure.
- Design exterior landscaping so it does not cause moisture build-up around the foundation. Maintain clearance between vegetation and exterior walls.
- Align and/or shield sprinkler irrigation heads to direct spray away from the building.
- Place foundation wall vents to provide cross ventilation for buildings with crawl spaces. If regrading or remodeling covers vents, additional vents may be needed.
- Provide adequate clearance to allow access for inspection and control if needed. Construct decks, fences, patios, planters, or other wooden structural components that directly abut the sidewall of the foundation or structure to provide: (a) an eighteen-inch clearance beneath or, (b) provide for six-inch clearance between the top of the component and the exterior wall covering or, (c) have components that are easily removable by screws or hinges to allow access for inspection of the foundation sidewall and treatment for termites.
- Eliminate gaps around floor joists. Floor joists should be built in or fitted onto joist hangers.
- Build floors to be durable, non-absorbent, anti-slip, without crevices, and capable of being effectively cleaned. If concrete is used it must be steel-float finished and sealed. Slope floors sufficiently for liquids to drain to trapped gullies or drainpipes. The floor area under food preparation equipment should allow easy cleaning of food spills and remain open to prevent harborage.
- In areas where hazard from termite damage is most critical, use floor framing of naturally durable wood and use other applicable methods of termite protection listed above for foundations.
- Provide adequate ventilation. Allow at least 18 inches of clearance under floor framing and at least 12 inches under floor girders. Proper ventilation and use of vapor barriers on the ground in the crawl space will help prevent the moist conditions that subterranean and dampwood termites favor. The minimum ventilation requirements in model building codes are based on the ratio of the net free vent area (a measurement of a vent�s unrestricted opening) to the area of crawl space to be ventilated.
- Install wall cavity closures and avoid joist/rafter gaps. Cavity closers should be installed at the top of all cavity walls and there should be no gaps between joists and rafters. This will keep out various pests that have gained access to the attic such as birds, mice rats and squirrels (squirrels are an increasing problem in roof assemblies).
- Eliminate gaps around wall penetrations. Wherever drains, hoists, and vents, conveyors, pipes, cable conduits or ducts pass between buildings through walls or foundations, they should be sealed to prevent the spread of any infestation from one building to another.
- Equip storage areas with self-closing doors to deny pest access.
- Eliminate cracks and crevices (e.g., with sealant, or copper or bronze wool) wherever possible, especially in kitchens and other food preparation and storage areas.
- Eliminate dead spaces inside storage areas to restrict areas where rodents may hide. Dead spaces include double walls, false ceilings, enclosed staircases, boxed plumbing, and voids (false bottoms) under cabinets.
- Do not use wall coverings that provide insect harborage. Do not install pegboard in kitchens, or other food service areas, animal rooms, or laboratories.
- Construct walls for easy cleaning. Wall surfaces are best when smooth, impervious, non-flaking and light-colored, and must be capable of being thoroughly cleaned. Do not use absorbent emulsion paints. Stainless steel splash-backs are recommended behind sinks and working surfaces. Coving should be used at wall to floor and wall to ceiling junctions to help cleaning operations and minimize debris accumulating. Avoid construction of wall-to-wall junctures less than 90 degrees. Slope floors in kitchen areas to provide good drainage after cleaning.
- Use durable, non-absorptive shelving material. Keep shelving far enough away from walls to leave room for cleaning.
- Areas where susceptible items are stored should be well lighted for ease in cleaning and inspection.
- Ventilate cavity walls. Adequate ventilation must be provided but any openings into the roof for this purpose must be screened with mesh or hardware cloth.
- Eliminate gaps around joists. On multi-story buildings, floor joists should be built in or fitted onto joist hangers.
- Seal all internal partitioning wall and ceiling cavities.
- Build for ease of maintenance. Suspended ceilings should be made of metal lattice incorporating cleanable panels. Aluminum backed and faced fiberboard has proved successful in many food factories. Flush-fitting ventilation grilles should be installed tightly enough to eliminate openings around the edge of the grille. Solid ceilings should be well insulated to avoid condensation and mold growth, and should be smooth, fire-resistant, light colored, coved at wall joints, and easy to clean.
- Build in inspection and maintenance access. Suspended ceilings are helpful in hiding horizontal pipe work and services but access for inspection for pests and maintenance must be built in. Structural walkways should always be provided in large premises.
- Seal utility entry points on the building exterior. Junctures where utilities such as pipes and cables enter structures require special consideration to prevent pest entry. Pests, especially rodents, often find easy access into buildings through holes beside water pipes and electrical conduit, and through the cold air return ducts on forced air furnaces. Utility entry points include exhaust vents and underground electrical lines. Power lines have always been a favorite route of travel for rodents, especially rats. Old, unused openings where utilities formerly entered the structure should also be inspected for cracks, broken screens, damaged doors, and uneven floors near doorways. Any external meter boxes must have close-fitting doors; all connected pipes or wires must be adequately sealed.
- Seal entry points within the structure. Once inside the wall, pests may gain
entry into the main structure along electrical lines, pipes, poorly sealed fire
wall sheathing, or around furnace ducts, hot water heaters, or laundry drains. If
pests are able to reach the attic, they may travel from room to room or unit to unit
through openings for pipes, ducts, and wiring.
Pipes, ducts or cables passing through walls should fit tightly or be built into fire stops. Protect joists with metal flanges where pipes or ducts pass through floors and walls. Hot water pipes should be carried in sleeves through vertical or horizontal partitions. Surround the base of elevators, conveyors and machinery with a 2-foot high smooth metal fence; conveyor ends should have tight-fitting doors. Seal around all electrical conduits, plumbing, heating pipes, trunking or service ducts that pass through them.
- Seal duct work. Ensure that all heating and air conditioning ducts are tightly sealed at seams and joints.
- Ensure that all pipe insulation has a smooth surface and that there are no gaps between pieces.
- When installing pipes, cables and fittings, build in or allow enough wall clearance to enable cleaning around the entry point. Flexible fittings are recommended for gas fittings. All electrical switches should be flush-fitting.
- Ensure that doors are properly installed and correct problems that interfere with a close fit. Pest entry problems can arise when doors are hung unevenly or too high, or lined with unprotected soft rubber weather stripping. Rodents, especially mice, often find easy access to buildings through open doors or under and beside poor-fitting doors, particularly in receiving areas and garage areas.
- Ensure that roll-up or overhead doors are well fitted. With the door closed, check for gaps along the sides, bottom, and top of the door. A gap at the top is common. Roll-up or overhead doors often provide easy entry for rodents, birds, and bats. Rats and mice can easily climb up the space between the door and the inner wall or track to the top, where they gain entry and climb down the inside of the track. Gaps between the track and the wall are also common, especially if the track has been installed on brick walls. Door bottoms may be bent or damaged, leaving gaps along the floor. Uneven floors due to frost heaves may leave gaps when the door is closed.
- Use self-closing doors. All doors should close on a level threshold, have smooth, non-absorbent surfaces, be tight fitting and self-closing. Doors of bin rooms below refuse chutes should be self-closing, flush-fitting and of metal construction.
- Select door styles for ease of maintenance and durability. Many food factories use polypropylene or toughened rubber doors for ease of maintenance.
- Correct mail slot/letter plates that are not at least 30 inches above ground level to prevent them becoming 'rat flaps.'
- Avoid the use of door frames with acute angles.
- Use woodwork that is well-seasoned, properly-knotted, stopped, primed, and given three coats of polyurethane paint.
- Modify conventional doors. External doors should be fitted with metal kick-plates not less than 1 foot high and the metal plates should also fit jambs and door linings.
- Use nylon bristle door sweeps; these are remarkably versatile for pest-resisting conventional doors.
- Install close-fitting windows and screens. Poorly fitted windows or screens allow easy rodent entry from exterior utility lines and pipes running along exterior walls. Runways going to window ledges are often observed on stucco and brick walls and in ornamental plantings next to buildings. Screens on windows, crawl spaces, and vents are often damaged in school buildings. Check these carefully for needed repair or replacement.
- Slope window ledges. Window ledges or other essential projections should slope at 45 degrees to discourage birds from perching and roosting on them.
- Modify windows to prevent harborage and access for pests, with no clear passageways to inside. Modify weep holes (openings that allow drainage of moisture) in window frames (e.g., with copper or bronze wool) to prevent access by paper wasps and other insects.
- Do not install exterior features that attract insects, rodents, birds or other wildlife.
Avoid installation (particularly near entrances) of:
- light fixture designs that may provide opportunities for bird perching, roosting or nesting;
- decorative lattices or other structural features that may inadvertently serve as bird roosts, over entrances to food services facilities; and
- structural features that provide opportunities for rodent harborage or burrowing. Install bird-proof barriers (e.g., netting) that are designed to prevent both pigeon and sparrow access to preferred nesting sites.
- Use enclosed fire escapes to eliminate bird perching, roosting and nesting, and access for other pests.
- Use durable pest-proof construction materials. Buildings are constructed from types of materials and design methods that vary greatly in the degree of susceptibility to pest infestation (for example, metal and concrete versus wood). Most structures eventually become less pest-proof due to deterioration, alteration, or lack of repair. Pre-fabricated building panels usually provide more opportunity for infestation to develop than do solid brick or concrete walls; certain partition or cladding materials such as chipboard, hardboard or blockboard offer little resistance to gnawing rodents and may, especially if damp, encourage molds, booklice and fungus beetles.
- Avoid rough finishes that can be gnawed or provide foothold. Rats and mice will climb up rough exterior surfaces so it is best to eliminate such finishes and to avoid projections or ledges which might give a foothold or provide access to any higher points of entry that are unlikely to be as well proofed as those on the ground floor.
- Screen or otherwise eliminate animal access under decks, porches, and stairways. Seal porches and ramps to the building foundation with �-inch hardware cloth screen mesh to form a barrier to digging pests such as rats and skunks. This screen must extend 12 inches into the ground and must have a right-angled, 6-inch wide, outward extending shelf to prevent burrowing under the screen.
- Use gravel to discourage burrowing. Where feasible and inaccessible to students, maintain a 2-foot pea gravel strip around buildings to prevent rodent burrowing.
- Install guards on pipes and downspouts. Standard conical or rectangular metal rat guards should be fitted to soil pipes and rainwater downspouts, projecting about 9 inches from the pipes and built into the walls at the point where they touch it. Fit tops of open pipes with balloon guards. Mesh fitted over rainwater downspouts will keep out nest debris.
- Design exteriors that have no access to wall cavities. To protect against mice, no external or other cavity wall should have any holes larger than � inch in diameter. Modify weep holes (e.g., with screening) in walls to prevent access by insect pests.
- Install fitted grills (small mesh) over air intakes.
- Consider pest management when landscaping near structures. (go to www.cdpr.ca.gov/schoolipm/, and click on �Managing Pests� on the left side of the page. Click on �Pest Prevention and Management,� then �Pest Prevention�Maintenance Practices and Facility Design.�)
- Avoid gaps at edges and corners. Wood or masonite siding is especially vulnerable to warping and cracking near corners and around the base of the building. Buildings constructed with ribbed or corrugated metal siding allow rodent entry if the bottoms of the siding panels do not rest flat on a solid surface or they are not otherwise closed off. Sections of prefabricated buildings should be assembled tightly, and gaps at joints should be covered with metal flashing; joint gaps are often left open, especially at corners and at the foundation/slab interface.
- Allow clearance for inspection between siding and soil surface in order to provide access to inspect for termite infestation, and to prohibit exterior siding contact with soil, clearance between exterior wall coverings (i.e., stucco, siding) and soil on the exterior of a building should not be less than 6 inches.
- Irrigation/sprinkler systems and risers for spray heads should have sprinkler heads or be located two feet from building so as to prevent water contacting walls; including drought tolerant plants in landscape plans can aid in achieving this goal.
- Eliminate rodent access under shingles. Shake shingle roofs allow rodent entry if the roof is not solidly sheeted with plywood or similar material and the shingles are not properly fitted. Use vents with tightly fitted double roof jacks and/or heavy-duty screen to prevent small animal access.
- Build tight roof joints and protect with flashing. Ensure tightness of all roof joints and the presence of flashing if rats and mice have access to the roof via wire, pipes, plants, or rough-textured walls. Ensure proper installation of metal flashing on roof, wall joints and edges.
- Fit eave roof tiles with bird stops (that will also exclude bats, bees and wasps).
- Make sure all attic and soffit vents are properly screened to exclude insects, birds, and other animals. Use �-inch hardware cloth screen mesh (coordinate with mechanical requirements).
- Direct water from drainage and sprinklers away from walls. All condensate lines, and roof down spouts should discharge at least one foot away from the structure sidewall, whether by underground piping, tail extensions, or splash blocks. Use gutters with down spouts on all buildings with eaves of less than six inches horizontal projection except for gable end rakes or on a roof above another roof.
- Locate site away from building entrances (at least 50 feet from doorways).
- Design site with properly graded concrete or asphalt pads to help prevent rats from establishing burrows beneath them.
- Build to exclude vertebrates. Build refuse sites with a solid enclosure that extends all the way to the ground. Use metal or synthetic materials, as opposed to chain-link or wood, to prevent rodents and other wildlife from gnawing or climbing the enclosure.
- Close off refuse, recycling, and trash storage areas. If trash will be stored, design storage areas that can be closed off from the rest of the building. Locate storage areas for boxes, paper supplies, and other materials in areas separate from where food or trash is stored. When stored together, these materials put food and shelter together, favoring pests.
- Place outdoor garbage containers, dumpsters, and compactors on hard, cleanable surfaces.
- Include a water source at the site for cleaning permanent storage containers and pad surfaces; ensure adequate drainage.
- Floor cavities should be sealed where they enter shafts or chutes.
- Shafts or chutes should be of smooth internal construction. To the extent feasible, build or modify these areas (e.g., use coving at floor to wall junctures, or other means of minimizing corners and sharp angles) to reduce debris accumulation and to facilitate cleaning.
Integrated Pest Management Kit for Building Managers. Massachusetts Department of Food and Agriculture, Pesticide Bureau, 100 Cambridge Street, Boston Mass 02202. http://www.pestinfo.ca/documents/IPMkitforbuildingmanagers.pdf
IPM Institute of North America, Inc. Part I. IPM Standards for School Buildings, http://www.ipminstitute.org/school_buildings.htm
IPM Institute of North America, Inc. Part II. IPM Standards for School Grounds, http://www.ipminstitute.org/school_grounds.htm
Marer, P. 1991. Residential, Industrial, and Institutional Pest Control, Oakland: University of California, Division of Agriculture and Natural Resources, Publication 3334.
NCPA Management Guidelines Series, http://cufp.Clemson.edu/dpr/SpecialPrograms/Ipm/setupipm/htm
Preventive Maintenance for Local Government Buildings: A Best Practices Review. Minnesota Legislature, http://www.auditor.leg.state.mn.us/ped/bp/pe0006.htm
Responsible Pest Management: Best Practices and Alternatives http://www.pestinfo.ca/main/ns/9/doc/5
Sustainable Building Guidelines: Project Design. California Integrated Waste Management Board, http://www.ciwmb.ca.gov/GreenBuilding/Design/guidelines.htm
U.S. EPA, Pest Control in the School Environment: Adopting Integrated Pest Management. http://www.epa.gov/pesticides/ipm/brochure/
Wisconsin�s School Integrated Pest Management Manual, Section 1: Essential Elements of IPM http://ipcm.wisc.edu/programs/school/sec1.htm