Pest Prevent_guidelines_12-5-12 (1).pdf

Pest Prevention by Design 1

Pest Prevention by Design

Authoritative Guidelines for Designing Pests Out of Structures

11/28/12 Version

Primary authors:

Chris A. Geiger, Ph.D

San Francisco Department of the Environment chris.geiger@sfgov.org, (415) 355 3759

Caroline Cox, MS

Center for Environmental Health

(510) 655-3900 x308 mailto:chris.geiger@sfgov.org

Pest Prevention by Design 2

About the San Francisco Department of the Environment

The San Francisco Department of the Environment (SF Environment) is a department of the City and County of San

Francisco, California. SF Environment’s mission is to improve, enhance, and preserve the environment, and to promote San Francisco’s long term well-being. SF Environment does this by developing innovative, practical and wide-ranging environmental programs, fostering groundbreaking legislation, and connecting the public to environmental resources by providing access to comprehensive and easy-to-use information on a wide range of sustainable practices.

In addition to our historic function of providing environmental policy direction for the Mayor and Board of

Supervisors, SF Environment delivers service programs for San Francisco residents and businesses including recycling, toxics reduction, environmental justice grants, and energy efficiency. See www.sfenvironment.org

About the International Code Council

The International Code Council is a member-focused association dedicated to helping the building safety community and construction industry provide safe, sustainable and affordable construction through the development of codes and standards used in the design, build and compliance process. Most U.S. communities and many global markets choose the International Codes. ICC Evaluation Service (ICC-ES), a subsidiary of the International Code Council, has been the industry leader in performing technical evaluations for code compliance fostering safe and sustainable design and construction.

Headquarters: 500 New Jersey Avenue, NW, 6th Floor, Washington, DC 20001-2070

District Offices: Birmingham, AL; Chicago. IL; Los Angeles, CA

1-888-422-7233 www.iccsafe.org

Funding support

This project was funded by the U.S. Centers for Disease Control REACH Core Grant # 1U58DP002990-01, as part of a larger project targeting San Francisco Housing Authority properties.

Disclaimer

The information contained in this publication is believed to be accurate; however, it is being provided for informational purposes only and is intended for use as a guide. Use of this document should not be construed as SF

Environment, the US Centers for Disease Control or the International Code Council engaging in or rendering architectural, engineering, legal or other professional services. Use of the information contained in this publication should not be considered by the user to be a substitute for the advice of a registered professional architect, a licensed engineer, licensed attorney, or other professional. If such advice is required, it should be sought through the services of a registered professional architect, licensed engineer, licensed attorney or other professional.

Trademarks: “International Code Council” and the “International Code Council” logo and the “International

Building Code” and the other codes in the family of ICC International Codes are trademarks of the International

Code Council Inc. Inclusion of ICC name and logo does not necessarily signify approval of this publication in its entirety.

http://www.sfenvironment.org/ http://www.iccsafe.org/Pages/default.aspx http://www.iccsafe.org/gr/Pages/adoptions.aspx http://www.iccsafe.org/

Pest Prevention by Design 3

Pest Prevention by Design – Technical Advisory Committee

Name Organization Sector

Allison Taisey, Ph.D Cornell Univ. Extension Academic/Extension

Arthur Slater Slater Pest Control Pest Control Industry

Bobby Corrigan, Ph.D Corrigan Consulting Consultant

Brad Guy Material Reuse Architect

Darren Van Steenwyk Clark Pest Control Pest Control Industry

Dion Lerman PA IPM Program, Penn State University Academic/Extension

Doug Henderson Alameda Co. Lead Prevention Program Government

Greg Axten American Geotechnical Inc. Engineer

Jim Fredericks, Ph.D National Pest Management Association Pest Control Industry

Jody Gangloff-Kaufmann, Ph.D New York State IPM Program Academia

John Cahill Cahill Inspection Services Inspector

Kathy Seikel US EPA - Childrens Health Government

Lee Tanner US EPA – Office of Pesticide Programs Government

Leo Saylor Cincinnati Metropolitan Housing Public Housing Maintenance

Luis Agurto, Jr. Pestec Pest Control Industry

Lyn Garling PA IPM Program, Penn State University Academic/Extension

Margaret Hurlbert Univ. of California, Berkeley Facility manager

Mark Palmer San Francisco Dept. of Environment –

Green Building Program Government

Mary Louise Flint, Ph.D University of California

Statewide IPM Program Academic/Extension

Megan White WebCor Builders Construction

Michael Merchant, Ph.D Texas A&M AgriLife Extension Academic/Extension

Nita Davidson, Ph.D California Dept. of Pesticide Regulation Government

Paul Romano New Jersey Institute of Technology Architect

Richard Estrada ATCO Pest Control Pest Control Industry

Sraddha Mehta San Francisco Dept. of Environment -

Environmental Justice Program Government

Tara M. Cahn Tara Cahn Architecture Architect

Thomas Green, Ph.D IPM Institute of North America Consultant

Vernard Lewis, Ph.D University of California, Berkeley Academic/Extension

Pest Prevention by Design 4

Revision History

Date Revision

November 5, 2012 Revision for second review by ICC

November 15, 2012 Revision incorporating ICC comments

November 28, 2012 (current) Final version, 1 st edition, for distribution

Pest Prevention by Design 5

Sections

Introduction 6

General Principles 11

Foundations and Slabs 17

Building Exterior: Siding 33

Building Exterior: Lighting 36

Building Exterior: Miscellaneous 39

Roofs 48

Landscape 49

Interior Walls 51

Floors: General 52

Floors: Institutional 53

Doors 55

Windows 58

Bedrooms 60

Bathrooms 62

Kitchens: General 65

Kitchens: Institutional 67

Utilities, HVAC, and Chutes 74

Refuse & Recycling 78

Miscellaneous 80

References 83

Pest Prevention by Design 6

Background

The world is blessed with many charming, pleasurable, glamorous and enticing subjects on which to ponder. Pest management is not one of these.

In fact, the case could be made that the average human actively avoids the subject, and with good reason. Pests are defined, after all, as organisms that humans do not want around . They are organisms that compete with us for resources, carry diseases, create unsafe conditions, or merely offend our aesthetics. In our minds (and sometimes in reality) pests are vile, repellent, creatures that may symbolize poor sanitation, dilapidation and neglect. We recoil at the sight of a mouse under the refrigerator or a cockroach in the pantry. At cocktail parties they make profoundly poor conversation starters.

It is no wonder, then, that when faced with pest infestations, or the prospect of future infestations, our response is less than thoughtful. We want them dead, and quickly. We prefer a simple, effective solution to our pest problems

– a silver bullet - so that we can move on to more appetizing topics. Our measure of success is quick action and maybe a few carcasses.

Agricultural ecologists realized decades ago the fallacy of this simplistic approach to managing complex biological systems, as described by Prof. Robert Van Den Bosch in his classic The Pesticide Conspiracy . Farmers soon realized that the silver bullet promised by DDT and other new pesticides could not last: Pests became resistant to the chemicals, requiring greater and greater amounts for the same effect; natural predators were decimated by the pesticides, resulting in even more extreme outbreaks of pests, and insects that had never been pests before were unleashed to create new problems, without the natural regulation of predators and parasitoids. In addition, by depending solely on chemicals and not addressing the root causes of problems – such as stressed plants, depleted soils or poor plant varieties – the conditions remained optimal for pest resurgences.

In response to these problems, scientists developed integrated pest management (IPM), a decision-making process that emphasizes prevention, knowledge of pest biology, and the use of least-disruptive control tactics, with pesticides saved as a last resort . While IPM has become standard practice in agriculture, it has been slower to take hold for structural pest management. Successful pest management on the farm can be measured easily at harvest time through crop yields and quality, but this is not the case in the city. Here success is more subjective, even psychological.

Homeowners may feel successful if they see dead ants on the floor, not knowing that their spray can has made no impact on the health of the ant colony. Still farther from their thoughts are the forgotten food scraps beneath the refrigerator that attracted the ants in the first place, or the scale insects living on the fruit tree just outside, whose sugary droppings help boost the colony’s population.

A restaurant owner facing a rat infestation wants the evidence destroyed before the next health department inspection. However, she may not consider sealing the gap in the door frame that let the animals enter in the first place, or putting a better lid on the dumpster out back, or removing the English ivy patch in the backyard (a preferred rat habitat). The result of our short-sighted approaches to this somewhat repulsive topic is that pests are managed neither safely, nor effectively, nor economically. Too often we ignore the most important, logical and environmentally sound step—prevention.

1 Sutherst 1995; Maine School IPM Program 2005 2 Van den Bosch 1978 3 Flint et al 200

Pest Prevention by Design 7

The Problem

Prevention of pest problems is the heart of any state-of-art integrated pest management programs, and the subject of these guidelines. Pest proofing in conjunction with sanitation efforts provides the best long-term management of urban pest infestations . Relatively simple design features can substantially reduce long-term pest control costs in buildings and landscapes, while also cutting the health and environmental impacts of pesticide use

Examples of pest preventative building/retrofit techniques are scattered through the scientific literature Many other techniques, often based on years of experience or anecdotal evidence, can be found in the pest control industry journals , handbooks

, and in various guidelines issued by public agencies

However, pest preventive tactics are rarely included comprehensively at the design stage of buildings. While various lists of these tactics have been compiled

, most have been piecemeal and none have been subjected to rigorous review. The specialized and often insular nature of the architectural, construction, facility management, and pest control industries further obstructs progress. What information is available is not targeted for those who need it most: The architects, engineers and builders who actually create the built environment.

Building codes generally require some of the more common procedures, such as a screening foundation vents

Other objectives, such as moisture reduction, have found their way into generally accepted best construction practices

. Experienced pest control professionals understand many of the prevention approaches, although they may not have occasion to put them into practice due to prevailing business models emphasizing treatment rather than prevention.

The recent explosion of interest in Green Building standards, such as the Leadership in Energy and Environmental

Design (LEED) program and the International Green Construction Code (IgCC) provides new opportunities for integrating pest prevention into a holistic design framework. Although LEED credits are available for IPM, no reference standards for pest prevention features yet exist for LEED. The same can be said for other common green building frameworks such as the National Association of Homebuilders NAHBGreen/ICC 700 and the Build It

Green programs.

Many of the principles presented here require architects and builders to rethink their design strategies in a more holistic fashion. This rethinking is needed both for established design approaches, such as the standard acoustical gaps in ceilings that can also serve as rodent or cockroach hotels, and emerging approaches, such as the promotion of living walls that will have unknown impacts on pest infestations. In other examples, tactics for designing out pests will likely harmonize very well with the sealing and weatherization tactics needed to conserve energy.

Clearly, an opportunity exists to both provide definitive design guidelines for pest prevention, to incorporate these guidelines into existing design frameworks, and in the end to reduce long-term costs and pesticide use in the built environment. Thus the goal for this publication: To create a set of authoritative, peer-reviewed guidelines for designing and building pests out of buildings.

4 Scott, 1991 5 Brenner et al, 2003 6 Ebeling, 1978; Mallis, 1997; Smith and Whitman 2007; Lewis 1997, 2003; Global Termite Expert Group for the United Nations Environmental Programs; http://www.chem.unep.ch/pops/termites/termite_toc.htm, Pratt 1949; Frantz 1988; Scott 1991 7 For example, Pest Control Technology Journal, http://www.pctonline.com/ 8 Smith and Whitman, 2007 9 Armed Forces Pest Management Board, 2009 10 Simmons, 2010 11 International Code Council, 2012 F101.1 12 Newport Partners LLC, 2006 13 http://www.usgbc.org/DisplayPage.aspx?CMSPageID=1988 14 www.iccsafe.org http://www.chem.unep.ch/pops/termites/termite_toc.htm http://www.pctonline.com/ http://www.usgbc.org/DisplayPage.aspx?CMSPageID=1988

Pest Prevention by Design 8

History of the Project

The idea for these guidelines began in 2005, when the San Francisco’s IPM Program collectively realized that the

City had stopped making real progress in pesticide use reduction on its properties. Pesticide use had declined by

80% in the first eight years of the program, but seemed to have bottomed out. After extensive consultations with field staff, we concluded that fundamental design problems in both buildings and landscapes were partly to blame.

Deferred maintenance on structures allowed rodents and cockroaches easy entry, while poor landscape designs exacerbated weed problems. Having gone as far as we could to restrict hazardous pesticides and promote least-toxic treatment strategies, it was time to better address pest prevention. At a daylong stakeholder event in 2009, IPM Program participants reached the same conclusion, and committed the program to emphasize prevention in both its landscape and structural IPM activities. The idea for an authoritative set of guidelines on the subject was further fleshed out at the 2009 National IPM Symposium in Portland, Oregon. After two years of grant writing, funding was finally received from the US Centers for Disease Control as part of San Francisco’s REACH grant.

Methods

The San Francisco Department of the Environment organized the Pest Prevention By Design Technical Advisory

Committee (PPBD TAC) in the Spring of 2011. Since the subject matter is highly interdisciplinary, committee members were sought from a variety of sectors: Pest control professionals, architects, engineers, pest management researchers/academics, green building experts, IPM experts/consultants, and public agencies.

At the same time, the Department undertook a comprehensive literature review on the subject. This review included scientific literature, manuals, websites, and professional publications. A web-enabled database was developed to organize the resulting list of pest prevention tactics. The database was also designed to track references, individual ratings and comments submitted by Committee members, and a variety of other details. Variables included in the database were:

Tactic Summary

Description of Tactic

Building area category (kitchens, foundations, exterior shell, etc.)

Sources of Information

Files, photos or videos

Tactic used at design vs. retrofit stage

Pests affected (Birds, ants, bedbugs, cockroaches, fleas, flies, mosquitoes, wasps & bees, dampwood termites, Formosan termites, drywood termites, subterranean termites, miscellaneous wood-destroying insects, miscellaneous insects, spiders, mice, rats, opossums & raccoons, miscellaneous mammals.)

Regions affected (East North Central, Central, Northeast, Northwest, South, Southeast, Southwest, West, West

North Central)

Scientific ratings of effectiveness

Anecdotal ratings of effectiveness

Anecdotal evidence

General comments

Compatibility with other design goals (for example, likely conflicts or synergies of particular tactics with energy efficiency or aesthetic goals)

Relevant tools and products

Facilities type (institutional, residential, or all)

Pest Prevention by Design 9

The Center for Environmental Health was contracted to coordinate the PPBD development effort. The first official meeting of the PPBD TAC was held in June, 2011, and the Committee met monthly 12 times in the following year.

At each meeting, the Committee discussed a new batch of pest prevention tactics.

Feedback from the web tool and from the meetings themselves was incorporated into the draft guidelines. The project also contracted with the

International Code Council to review all of the guidelines in detail before publication, and to identify any clear redundancies with accepted building practices and building codes. A pest-proofing and IPM pilot project was initiated on San Francisco Housing Authority properties to obtain data on costs and benefits of pest prevention retrofits.

How to Use These Guidelines

This publication is intended for architects, engineers and builders who wish to take green building to the next level, but can be used by anyone who wishes to incorporate well-informed design choices into the design and retrofit of buildings. We undertook the project to fill a glaring gap in the pest management world: To our knowledge, no other comprehensive guidelines on pest preventive design tactics exist.

Pest prevention is a broad subject, and we had to draw some boundaries. It is worth reminding the reader of the scope and limitations of this document. To make best use of these guidelines, the user should understand what these guidelines are and are not.

Structural emphasis. The PPBD Technical Advisory Committee decided early on that this resource should best focus on pest prevention in structures. Prevention of pests in landscapes – while important and similarly underaddressed – was intentionally excluded from this volume. The only exceptions are cases where landscape features adjacent to structures affect pest infestations inside the structures themselves. For example, several species of ivy, including the common English ivy (Hedera helix) as well as other common ground covers such as Pachysandra and Liriope spp., are known to provide an ideal habitat for rats, and plantings adjacent to buildings dramatically increase the chance of rat infestations.

Guidelines, not standards. Best practices vary widely depending on the purpose of the building, its location, prevailing pests, climate, and the relative importance of sometimes-competing goals such as construction cost, energy conservation or aesthetics. For this reason, we present these pest prevention tactics as guidelines, not rules or standards. In some cases, we have listed instances where a tactic is likely to conflict with other design goals, such as energy conservation or aesthetics.

North American emphasis. We emphasize North American pests and building practices, although many of the tactics listed could be applied anywhere.

When appropriate we have labeled specific tactics that may be more appropriate for certain regions; for example, builders in the Southern states face higher termite pressures and should pay closer attention to features such as separation between soil and wood, termite barriers beneath foundations, and avoidance of stucco construction.

15 Many of the discussions were quite lively: As one committee member commented, this project sometimes became as much an exercise in cross-disciplinary communication as a traditional research project.

Key to the Guidelines

Tactics are organized by building area category

For example, kitchens, exterior shell and foundations. A set of general principles are also provided.

Information sources:

We have provided references to scientific literature when possible. Lacking that, we provide references to professional literature or websites. Some tactics were suggested by the PPBD

Technical Advisory Committee during our discussions; these are labeled as Technical

Advisory Committee comments.

Compatibility with other design goals: In this space we note any known potential conflicts with other design goals, or code sections that are closely related.

Pest Prevention by Design 10

Design and retrofit emphasis. These guidelines include features that can be incorporated at either the design stage of a new building, or during a retrofit of existing buildings. In many cases, the tactics can apply to either. We have purposefully excluded routine building management or maintenance activities from the guidelines, even though they may be important components of integrated pest management programs. For example, while regular cleaning of refuse containers may be an effective preventive tactic for flies, is not included because it would be considered part of routine sanitation – not a design feature. Similarly, we specifically excluded pest control activities, such as wall void treatments with boric acid dusts or installation of bug zappers. We felt that these strategies are expertly addressed by other publications, and are predominantly in the realm of pest control professionals, not builders.

References for more detailed information. Certain facilities, such as food processing or pharmaceutical manufacturing facilities, require pest exclusion specifications that are more detailed than we have provided here.

Engineers and architects involved in such projects are referred to Imholte and Imholte-Taushcher (1999).

Pest Prevention by Design 11

Although these guidelines are organized by building area, there are some principles that apply throughout.

Animals of all kinds, whether vertebrate or invertebrate, are living organisms with biological needs and behavioral preferences. All require FOOD, WATER, HARBORAGE, and ENTRY in order to take up residence and become pests

. All of the pest prevention tactics listed herein are based on minimizing these factors. Sometimes, eliminating just one of these factors can be sufficient to prevent infestations.

Principle #1: Understand local pest pressures.

Architects, builders and engineers need not be entomologists or pest experts, but a rough familiarly with local structural pest species is essential in order to make the best design choices. University extension services or reputable local pest professionals are the best sources for this information.

Climatic factors limit the distribution of many pest organisms. For example, ants, some cockroaches, termites, rats, mice, birds, and urban wildlife species are all strongly affected by climate. Generally speaking, insect pests are most troublesome in warm, humid climates. Warm temperatures speed up insects’ life cycle, resulting in higher populations

The distribution of certain termite species is especially important, since termite pressure has a bearing on many design and materials choices. The International Residential Building Code map of termite problems (Figure 1) is a good place to start.

16 Purdue University Entomology Extension 2000-2001

17 Below a lower temperature threshold and above a higher temperature threshold, insects cannot develop (Shelford 1931). In between the two extremes, insect development rates increase with warmer temperatures. As development rates increase, the time to reproductive maturity decreases. For example, German cockroaches show a preference for areas that are at least 70oF (21oC). At this temperature it takes about 100 days for a cockroach to grow from an egg to a mature adult, but at 80oF (27oC) only 60 days are required. (Smith and Whitman 2007 4.9) Argentine ants can take as little as 30 days to develop from egg to adult, or as many as 140. (Smith and Whitman 2007 1.3)

Figure 1. International Residential Building Code map of termite problems.

Source: International Code Council, 2012 International Residential Code For

One- And Two- Family Dwellings Figure R301.2

Pest Prevention by Design 12

Table1. Summary of common termite species in the United States and their distribution

Principle #2: Analyze the physical context for each building situation.

Along with climatic factors, the physical context of a particular building can also be a critical design consideration;

that is, the surrounding buildings, surfaces, vegetation, and underground utilities. A building constructed in

Manhattan, for example, automatically faces high potential rat infestations due to the intricate tangle of subway tunnels, sewers, and utilities underlying that dense city, as well as the current practice of collecting refuse in plastic garbage bags rather than dumpsters. For such a situation, architects must pay special attention to excluding rats by sealing off all possible entries from the outside. Similarly, buildings constructed near major urban squares – subject to high litter loads from visitors and the occasional dedicated pigeon-feeder – are apt to become prime roosting places for pigeons. Such infestations might be avoided by designing out semi-enclosed alcoves, flat ledges, and other preferred roosting locations

. Finally, more rural or suburban locations with dense vegetation (especially carpet-style ground covers and climbing vines) are likely to experience intrusions from a variety of small mammals, such as rats, mice, chipmunks, ground squirrels, raccoons, opossums, and tree squirrels. In these situations, careful attention to screening all gaps from the foundation to the roof vents is strongly advised

18 Associated Press 2010

19 University of Florida 2008

20 Hygnstrom et al., 1994

Common and species name Geographic distribution

Reticulitermes spp. (subterranean) Throughout the US except Alaska, with highest populations in the Gulf and Southeastern states

Heterotermes spp. (subterranean) South Florida and the desert Southwest

Formosan termite, Coptotermes formosanus

(subterranean)

Southeastern US and Southwestern California

Southeastern drywood termite, Incisitermes snyderi Southeastern US

Western drywood termite, Incisitermes minor Central Arizona west to California and north to

Washington State

West Indian drywood termite, Cryptotermes brevis Hawaii, Florida and west to Louisiana

Desert drywood termite, Marginutermes hubbardi Desert regions of southeastern California and Arizona

Dampwood termites, Zootermopsis, Paraneotermes, Prorhinotermes spp.

Southern Florida

Source: Univ. of Florida IFAS Extension 2009, Potter 1997

Pest Prevention by Design 13

Principle #3: Design for the necessary pest tolerance level.

An occasional trail of ants in the home may be a mere nuisance, but even a single ant in a surgical ward can have grave consequences. The tolerance to pest infestations varies, and ideally should be considered at the design stage. Institutional kitchens, health care facilities, and mission-critical manufacturing facilities demand detailed and careful design and planning to exclude potential pests

Principle #4: Use durable pest-resistant materials.

Selecting pest-resistant materials can exclude pests from entering a structure, or deny pests harborage once they are there. Some materials provide “resistance to pests” while other materials provide 100 percent exclusion. Selecting materials carefully based on factual information is essential for building engineers, designers and builders.

Many ineffective approaches exist in the pest control world. For example, using spray can foams alone—without the inclusion of impervious stainless steel or copper wool—is one of the worst techniques for excluding rodents from buildings, yet the approach is very common among building superintendents as well as homeowners.

The pest resistance of particular materials also depends on the species of pest in question. Termites, for example, are known to avoid certain woods. Besides being generally more durable than other woods, western red cedar, redwood, and incense cedar, Port Orford cedar, black locust, northern white cedar, and Alaska cedar are known to dissuade termite infestations

. Using these woods makes infestation less likely but does not guarantee that infestations will not occur. It is also important to note that only the heartwood from these species is resistant.

Pressure treated woods are widely used for construction uses that involve soil-wood contact or exposure to moisture.

There is a wide range of treatments now available, most of which involve chemicals that have environmental or human toxicity issues. For example, chromate copper arsenate (CCA) treatments pose cancer and reproductive hazards to workers and the public, while compounds with high copper content (such as amine copper quat, ACQ) pose higher aquatic toxicity hazards.

Borate treatments are viable alternatives for interior use, or situations with low exposure to moisture, which can leach the material out of the wood. New products using silicates also appear promising

. In some situations, pressure treated woods remain the most economical choice, but like other woods their resistance erodes with time.

For some applications, such as siding, non-wood alternatives are available that are impervious to insect entry, if not rodents. Fiber cement, aluminum and steel can be appropriate choices for siding in some situations. Stucco, while resistant to insect penetration from the outside, is generally a poor choice in high termite pressure areas for two reasons: Improperly constructed, moisture can accumulate in the enclosed wood, and the stucco shell makes inspection virtually impossible. Some materials such as high density plastic will deter gnawing by rats and mice, and neither rodents nor insect pests are likely to penetrate high quality elastomeric sealant compounds when applied correctly. Recent research has shown that the formidable burrowing Norway rat can be completely deterred from burrowing into soil via the use of a stainless steel mesh carpeting material. Further examples are listed in the tactics section of these guidelines.

21 Imholte, et al., 1999 22 Scheffer and Morrell, 1998 23 Dickey, 2003 24 Review of TimberSil, GreenSpec database at http://www.buildinggreen.com/auth/productDetail.cfm?productID=2743 (BuildingGreen.com)

R. Corrigan, pers. communic., 2012.

http://www.buildinggreen.com/auth/productDetail.cfm?productID=2743

Pest Prevention by Design 14

Principle #5: Design for easy inspection.

“What you don’t know won’t hurt you” is a shaky philosophy at best, and certainly does not apply to effective pest management. Hidden drains or inaccessible utility boxes can thwart pest control efforts in institutional kitchens, coved baseboards can provide hiding places for bedbugs, ants or small flies, and inaccessible foundations or deck supports can mask termite infestations. Built-in access to critical areas, such as foundations, false ceilings, or triple wall voids, greatly assists pest control professionals in the early detection of wood-boring insects or rodent infestations, potentially saving thousands of dollars in wood replacement and protecting the health of building inhabitants. Lack of easy inspection options can result in increased pest control costs over the life of the building, higher use of pesticides, and greater health and environmental impacts.

Principle #6: Minimize moisture.

All competent builders and architects know that moisture must be excluded from buildings, and many common building codes are aimed at this goal. In addition to promoting building decay, moisture also promotes serious problems with insect pests such as termites, wood-boring beetles, cockroaches, flies, carpenter ants, silverfish, and millipedes, to name but a few. Perhaps even more important, excessive moisture inside buildings can lead to serious mold contamination issues—some of which can require many thousands of dollars in remediation. Multiple procedures can be used to minimize building moisture including proper guttering, downspout placement, correct ventilation of crawl spaces, one-piece countertops, humidistats, vapor barriers for crawl space flooring, appropriate slopes for patios and so forth.

Principle #7: Seal off openings.

Most building codes require that certain intentional openings, such as crawl-space and soffit vents, remain screened to exclude rodents and other wildlife pests. However, effectively sealing off all openings to the building exterior, as well as openings between interior rooms, improves the odds of maintaining a pest-free environment.

Elastomeric sealant can be an indispensable tool in sealing small cracks, gaps around countertops, or pipe breaks against insect entry; stainless steel wool and fire block foam can be used for larger openings. The use of escutcheon plates around all pipes where they enter through walls is essential. Foundation expansion joints can be further safeguarded against termites with stainless steel mesh. Doors with minimal gaps, including functioning door sweeps where necessary, and tight fitting windows are also important exclusion features

Many designers are surprised to learn just how small a gap pests can penetrate. For example, the width of a pencil

(about ¼”) is sufficient to allow mice to squeeze under doors. For convenience, we have provided a table of gap sizes required by various pest species in Table 2 below.

26 Weather-stripping a door is not equivalent to “pest proofing” a door. High density pest brushes or other door sweeps are critically important.

Pest Prevention by Design 15

Table 2. Summary of maximum gap sizes for excluding various pests

Common

Name Scientific name

Maximum opening size/mesh size Reference

In s e c ts a r th r o p o d s

Biting midges Ceratopogonidae 0.605 mm ~30 mesh AFPMB, 2009

Cheese skipper Piophila casei 0.595 mm ~32 mesh Ebeling, 1975*

Cockroaches Blatella germanica 1.66 mm ~12 mesh Koehler, 1994**

Cotton aphid Aphis gossypii 0.341 mm ~50 mesh Bethke & Paine, 1991*

Fruit flies Drosophilida spp. 2.12 mm ~10 mesh NPS, 2006

Honeybees Apis spp. 3.00 mm ~7 mesh NPS, 2006

House flies Musca domestica 2.03 mm ~10 mesh Block, 1946

Mosquito Aedes egyptii 1.03 mm ~18 mesh Wesley & Morrill, 1956; Block, 1946

Mosquito Anopheles quadrimaculatus, Culex quinquefasciatus

1.38 mm ~14 mesh Block, 1946

Redlegged ham beetle Necrobia rufipes 0.595 mm ~32 mesh Ebeling, 1975*

Sand flies Phlebotominae spp.

(Psychodidae)

0.605 mm ~30 mesh AFPMB, 2009

Termites (Eastern subterranean) Reticulitermes flavipes 0.610 mm ~30 mesh Tucker, 2008*

Termites

(Formosan) Coptotermes formosanus 0.660 mm ~28 mesh Grace et al, 1996*

Thrips Frankiniella occidentalis 0.192 mm ~80 mesh Bethke & Paine, 1991*

Yellowjackets Vespidae spp. 3.00 mm ~7 mesh NPS, 2006

Scorpions Scorpionida spp. 1.6 mm Timm & Marsh, 1997

B ir d s Pigeons Columba livia 50.8 mm (2 in) Timm & Marsh, 1997

Sparrows, Starlings

Passer spp., Sturnus vulgaris

19.1 mm (0.75 in) Timm & Marsh, 1997

M a m m a ls

Bats Chiroptera spp 6 mm/0.25 in Greenhall & Frantz, 1994

Mice Mus musculus 6 mm/0.25 in Greenhall & Frantz, 1994

Rats Rattus norvegicus, R. rattus

9.5mm/3/8 in gaps under doors; 18 gauge

13 mm/0.5 in mesh

Corrigan, 1997

Studies marked with an asterisk identified nominal gap sizes; these were matched with the closest Tyler mesh size. All other studies referred specifically to minimum mesh sizes; these were matched with approximate gaps sizes. Mesh opening sizes are nominal, i.e., not diagonal

Study pertained to preferred harborage for nymphs, not minimum opening for access, which is likely smaller

Pest Prevention by Design 16

Principle #8: Eliminate potential harborage.

Pests need a place to live, preferably a hidden space where they will not be disturbed. Minimizing inaccessible spaces can therefore assist pest management efforts: False ceilings, false bottoms under cabinetry, uncapped concrete blocks, air plenums, and gaps behind permanent machinery are examples. In some cases, the material itself creates a potential harborage, as is the case when rigid foam insulation is used on the outside of foundations – where termites can burrow in and take up residence. Incorporating some of these measures will be simple, while others (such as eliminating air plenums or rigid foam insulation) may directly conflict with other building goals.

Principle #9: Engineer slabs and foundations to minimize pest entry.

The design of foundations and slabs is critical in pest prevention practices and affects a wide range of pests, including ants, termites, mice, rats, and cockroaches. Termites, in particular, will have easy access to those structures with defective foundations or slabs with improper expansion joints. Sufficient separation between the soil and a structure’s wooden elements is required by most building codes to inhibit subterranean termite incursions. In addition, architects and builders must minimize concrete cracks that can allow entry of termites or other pests. A variety of tactics can achieve this goal, including the use of appropriate concrete admixtures, monolithic pours, minimization of expansion joints, use of termite-resistant mesh over joints, and the use of termite resistant barriers beneath the slab. In areas with high rodent pressure, curtain walls beneath the foundation of conventional style buildings (i.e., buildings with crawl spaces, not basements) are very helpful.

Principle #10: Design buildings to be unattractive to pests.

What makes a building “attractive” to pests, other than food, water, and potential harborage? Excessive or poorly designed exterior lighting can attract hordes of night flying insects to doorways, windows, or exterior hallways.

Roof rats, mice and squirrels find vines up the side of a building to be attractive highways and even food sources.

Bushes and shrubs planted too close to building foundations become pest magnets, offering near-ideal concealment and protection from the elements. Trees placed too close to buildings will eventually have limbs touching roofs and walls, which may become pest conduits. Poorly placed composting operations or refuse bins can similarly attract rodents to the environs of a structure, making entry that much more likely. Semi-enclosed, horizontal roof surfaces, especially near outdoor eating areas, are invitations for pigeons.

Acknowledgements

This project was funded by the U.S. Centers for Disease Control REACH Core Grant # 1U58DP002990-01, as part of a larger project targeting San Francisco Housing Authority properties. Ryan Nestle and other staff at the Center for Environmental Health coordinated the project and provided indispensable support services. Intern Nicole Hanks’ hard work brought the project to completion, and interns Ben Harris, Janett Nolasco, Dashiell Farewell, Corinne Smith and Lauren Taylor provided invaluable assistance. The PPBD Technical Advisory Committee was outstanding in its participation, patience, and dedication to the project, and space does not allow a full listing of their contributions. Mike Merchant of Texas AgriLife Extension and Luis Agurto Jr. of

Pestec have been central to the project since before it became a project. Tom Green kindly provided lists of pest prevention tactics developed by the Green Shield Program at the IPM Institute of North America. Greg Axten of American Geotechnical provided some key photos, illustrations, and expertise. Bobby Corrigan, Vernard Lewis, John Gibson, and Shahla Layendecker were especially helpful in their editing suggestions. Daniel Friedman, editor of InspectApedia.com, generously provided images, and welcomes questions or content suggestions from readers for his website, which covers related issues.

Pest Prevention by Design 17

Principle 1.1 Drainage design.

1.1.1 Slope of concrete and asphalt areas near buildings.

Provide 1/4" slope at patio slabs, walks, and driveways away from building.

Effective on: Dampwood Termites, Subterranean Termites and Misc. Wood Destroying Insects

Compatibility Issues with

Other Design Goals:

5% slope for the ground adjacent to the foundation for a minimum distance of 10 feet is required.

(International Building Code Section 1804.3 (2012))

References: Environmental Protection Agency, 2010

1.1.2 Backfill around foundations.

Tamp backfill to prevent settling and slope the final grade away from the foundation at a rate of 1/2 inch per foot over a minimum distance of 10 ft.

Effective on: Dampwood Termites, Subterranean Termites and Misc. Wood Destroying Insects

Compatibility Issues with

Other Design Goals:

Commonly required by local building codes

References: US Environmental Protection Agency 2010, and Potter 1997

Pest Prevention by Design 18

Principle 1.2 Reduce moisture in crawl spaces and under concrete slabs.

1.2.1 Vents maintenance.

Air should flow freely (not blocked by shrubbery, mulch, or other landscape materials) through vents to reduce moisture levels. Maintain vent openings to crawl spaces.

Effective on: Cockroaches, Dampwood Termites, Drywood Termites, Subterranean Termites, Misc. Wood Destroying

Insects

Compatibility Issues with

Other Design Goals:

Aesthetic issues

References: Simmons, 2005

1.2.2 Subgrade membranes under concrete slab foundations.

Use a continuous, durable subgrade membrane sealed at all splices, perimeters, and protrusions in order to minimize foundation moisture problems. The membrane product selected should be specifically manufactured for use as a subgrade membrane and conform to ASTM E1745, latest edition, 0.1 perm maximum. Installation should conform to ASTM E1643, latest edition.

Effective on: Ants, Dampwood Termites, Subterranean Termites, Misc. Wood Destroying Insects, Spiders, Misc. Insects

Compatibility Issues with

Other Design Goals:

Building codes require this membrane to be a minimum Class 1 vapor retarder per ASTM E96

(International Residential Code R506.2.3 and International Building Code 1907.1 (2012)

References: Technical Advisory Committee

Pest Prevention by Design 19

Principle 1.3 Prevent pest access to crawl spaces.

1.3.1 Corrosion resistant, pest-resistant mesh on crawl space vents.

For any ground-level space (e.g. raised foundation crawl space) requiring foundation vents, specify corrosion resistant vent material (e.g. bronze) and a vent opening size smaller than the pest to be inhibited. For example, for typical ants and termites, use #50 bronze mesh between layers of ½ to 1-inch mesh for durability. Building codes generally require mesh with maximum opening of 1/4 inch, which will block rodent access.

Effective on: Dampwood Termites, Drywood Termites, Subterranean Termites, Misc. Wood Destroying Insects. Misc.

Insects, Mice, Rats, Opossums, Raccoons, and Misc. Vertebrates

Compatibility Issues with

Other Design Goals:

As necessary, vent area should be increased to compensate for reduced air flow caused by smaller mesh sizes

References: Technical Advisory Committee, and International Residential Code R408.2, International Building Code

1203.3.2

1.3.2 Clearance between crawl space ventilation and finished ground level.

Foundation vents should be at least 150 mm (6 inches) above finished ground level.

Effective on: Dampwood Termites, Subterranean Termites and Misc. Wood Destroying Insects

Compatibility Issues with

Other Design Goals:

None identified

References: Verkerk, 1990, p. 78-99

Pest Prevention by Design 20

Principle 1.4 Access for inspections in the design of accessory structures that abut the foundation sidewall or other structures.

1.4.1 Clearance at accessory structures.

Provide 18" clearance beneath and 6" clearance between accessory structures and exterior wall coverings at decks, fences, patios, planters, and other accessory wood structures. If this clearance is not possible, construct accessory structures so that they are easily removable to allow inspection for termites.

Effective on: Dampwood Termites, Drywood Termites, Subterranean Termites, and Misc. Wood Destroying Insects

Compatibility Issues with

Other Design Goals:

Building codes require minimum clearances of 12 inches for wood beams and 18 inches for joists and floors to the exposed ground. (International Residential Code R317.1 and International Building Code

2304.11.2.1 (2012)

1.4.2 Access to foundations.

Provide easily removable components to allow access to foundation for inspections.

Effective on: Subterranean Termites, and Misc. Wood Destroying Insects

Compatibility Issues with

Other Design Goals:

1.4.3 Concrete substructures.

In order to minimize entry of pests via joints, pour concrete patios as part of the main slabs.

Effective on: Dampwood Termites, ,Subterranean Termites, and Misc. Wood Destroying Insects

Compatibility Issues with

Other Design Goals:

Cost issues and logistical issues

Pest Prevention by Design 21

Principle 1.5 Eliminate wood and cellulose-containing material under and near structures.

1.5.1 Wood material adjacent to building.

No cellulose-containing material (wood scraps, form boards, vegetation, stumps, large dead roots, cardboard, trash, and foreign material) should be buried on the construction site within fifty feet of any building, especially in areas with high termite pressure.

Effective on: Dampwood Termites, Subterranean

Termites, and Misc. Wood Destroying

Insects

Compatibility Issues with

Other Design Goals:

None identified

References: Simmons, 2005, and Technical

Advisory Committee

Source: Inspectapedia.com

1.5.2 Fill material.

Fill material used around structures should be clean and free of vegetation and cellulose material.

Effective on: Dampwood Termites, Subterranean Termites, and Misc. Wood Destroying Insects

Compatibility Issues with

Other Design Goals:

References: Simmons, 2005, and International Building Code 1804.2

Pest Prevention by Design 22

1.5.3 Remove wood materials from masonry.

Prior to concrete placement, clean all cellulose-containing material from cells and cavities in masonry units to inhibit termite colonization.

Effective on: Dampwood Termites, Subterranean Termites, and Misc. Wood Destroying Insects

Compatibility Issues with

Other Design Goals:

Building codes refer to industry standards TMS602/ACI 530.1/ASCE6 for masonry foundation walls.

(International Building Code 2104.1.2 and International Residential Code R404.1.1)

1.5.4 Remove extraneous wood materials after foundation construction.

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.

Effective on: Dampwood Termites, Subterranean Termites, and Misc. Wood Destroying Insects

Compatibility Issues with

Other Design Goals:

Pest Prevention by Design 23

Principle 1.6 Consider termite susceptibility in choice of foundation materials.

1.6.1 Steel posts in post and beam foundations.

Use steel posts for post and beam foundations, especially in areas with high termite pressure. The ends of the posts should be sealed at both ends with welded plates and the posts should be set in concrete foundations.

Effective on: Dampwood Termites, Subterranean

Termites, and Misc. Wood Destroying

Insects

Compatibility Issues with

Other Design Goals:

Cost issues

1.6.2 Synthetic stucco.

In areas of high termite hazard, avoid Exterior Insulation and Finish Systems (EIFS, commonly referred to as synthetic stucco).

Effective on: Dampwood Termites, Subterranean

Termites, and Misc. Wood Destroying

Insects

Compatibility Issues with

Other Design Goals:

Aesthetic issues

References: Suiter and Forschler, 2009, and

Potter, 1997, p. 281-282

Pest Prevention by Design 24

1.6.3 Foam insulation and foundation systems.

In areas of high termite hazard, avoid subgrade foam insulation on the exterior of the foundation, or pre-formed closed cell foam foundation systems.

Effective on: Dampwood Termites, Subterranean Termites, and Misc. Wood Destroying Insects

Compatibility Issues with

Other Design Goals:

Subgrade foam treatments are sometimes recommended for energy conservation. Possible cost issues with eliminating use of foam foundation systems

References: Suiter and Forschler, 2009, and Potter, 1997, p. 281-282

Principle 1.7 Minimize cracks more than 1 mm wide in concrete foundations and slabs.

1.7.1 Expansion joints.

Minimize need for expansion joints when designing slabs. When expansion joints are used, inspection access should be readily available and the use of termite-resistant mesh should be considered. In one study, 83% of subterranean termites entering buildings came in through expansion joints in concrete slabs.

Effective on: Dampwood Termites, Subterranean

Termites, and Misc. Wood Destroying

Insects

Compatibility Issues with

Other Design Goals:

May conflict with the need to engineer for soil shifting. Best for new construction.

References: Forschler, 2011, Verkerk, 1990, p.

78-99, and International Building

Code 1901.2 (2012) 1804.2

Pest Prevention by Design 25

1.7.2 Voids in concrete.

In order to minimize voids in concrete slabs, mechanically compact concrete with a vibrator when pouring a slab.

Effective on: Dampwood Termites, Subterranean Termites, and Misc. Wood Destroying Insects

Compatibility Issues with

Other Design Goals:

Common practice for commercial construction, but may be difficult for residential renovations

1.7.3 Curing of concrete slabs.

Cure concrete slabs slowly to reduce shrinkage and cracks. Moist curing periods should generally not be less than seven days. Consult a structural engineer for design standards.

Effective on: Dampwood Termites, Subterranean Termites, and Misc. Wood Destroying Insects

Compatibility Issues with

Other Design Goals:

1.7.4 Anchors in concrete slabs.

Embed anchor bolts in slabs as the slab is poured. If additional anchors are necessary, use adhesive anchoring systems rather than expanding…