Preserving Our History: The Exclusion Conclusion

By Patrick Kelley, ACE

In a pest management program exclusion of pests from the outside can be one of the most important factors for maintaining a pest free environment. External pest pressure is a major threat for both urban and rural museums. The pest entry of a single rodent can cause significant damage in a short period of time and diminish the previous hard work that went into the program. This leads one to the conclusion that an exclusion program is an essential component in IPM.

A thorough inspection of the exterior of a facility and some simple supplies can provide a permanent solution to most areas of pest entry. Listed below are some of the more common conditions that allow rodent and insect entry and some recommendations for repair. Please note that most of these treatments will also benefit your energy conservation by better preventing heat loss in the winter and the loss of cool temperatures in the summer.

Gaps beneath doors: This is the single most common condition that allows the easy entry of insects, rodents and even birds into structures. Warmth and food odors can migrate outdoors through these gaps and draw in pests of all types. Remember that rats only need a 1/2 inch (12.7 mm) gap for entry, mice need 1/4 inch (6.35 mm) gap and many museum insect pests can enter through a 0.08 inch (2 mm) gap or even less. A quality door sweep will remove any gap beneath the door. The best type of door sweeps are strips made from nylon brush material. They have outstanding abrasion resistance and they remain flexible at a wide range of temperatures. Once the bracket that holds the brush strip is mounted, the brushes themselves can be changed quite easily.

Gaps around the frame of a window: Window frames on the exterior of a building can often have gaps that allow pest entry on either side, above or below the frame. A professional foam material (E.G. Pur-Black Foam applied through a Pageris Foam Gun) should be applied in any gap.

Gaps around a pipe chase: The point of entry where a plumbing HVAC or electrical pipe passes through an outside wall and into a structure is called a pipe chase. Often, after the hole is drilled through the wall and the pipe is installed, the gap between the pipe and the wall is not sealed or it is incorrectly sealed. Also, sealing material can shrink with age and
an area that was once sealed can become a pest highway. Professional foam sealants will deter insect pests. Also, if rodents are an issue, copper gauze can be stuffed around the pipe and foam sealant applied to secure it in place.

Windows and doors left open by staff: When staff members become hot or cold, they will often open doors and windows to adjust their temperature. A better temperature-controlled work environment and a written policy preventing doors and windows from being left open will help alleviate this problem.

Broken or insufficient screen material: A metal screen that becomes missing or torn should be quickly replaced or repaired. Also, screening with a mesh size that is too large will allow pest entry. The size screening recommended for insect pests is Tyler Mesh size—16 mesh or higher. Screens with a larger gap than this should be replaced.

Cracks in concrete foundation: Broken or cracked concrete at the base of an exterior wall will often allow pests easy access into a wall void or directly into the structure itself. Cleaning and removing the crumbled concrete material and replacing it with sound concrete
will solve most issues.

Gaps around the roof-line and beneath shingles: Often, older historic homes with slate roofs have small gaps at the roof line where wasps, Asian ladybird beetles, boxelder bugs, and cluster flies can enter.


2 thoughts on “Preserving Our History: The Exclusion Conclusion

  1. First, thank you so much for your blog! It’s a great service especially for those of us with limited resources. Regarding door sweeps for an interior door, how do you determine on which side of the door you should install the sweep? (The door to our collections storage opens into the storage area, and there is not difference in floor level between hallway and storage.)

    • Thanks for your question. With a situation like yours, where I assume your biggest concern is from pests entering the collections storage from the hallway, I would recommend placing the sweep on the outside of the door (hallway side). I say this because this will prevent pests from accumulating beneath the door. Insects or even rodents that are hiding out in the gap beneath the door could possibly enter the collections storage area anytime anyone opens that door to go inside or leave. The brush placed on the outside of this door will cause whatever pests that are in the hallway to continue moving on down the hall to the next available hideout. Of course a brush sweep on an exterior door may prevent pests from getting into the hallway in the first place. The sweeps will eliminate pest penetration no matter what side of a door they are installed on, but one must look at each door and take into account any door thresholds, which way they open and where the pest potential is coming from prior to making a decision on which side to install them. – Patrick Kelley

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