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How Subterranean Termites Get Into Structures
A Guide for Architects and Builders
Dina Richman
University of Florida
How Does the Problem Start?
A. Existing Colony– Tubes connect colony to structure– Most frequently near moist wood and soil
B. New Colony– King and queen choose area and excavate– Seek moist wood and soil
• Require Food, Water, and Access
Existing Colony: Mud Tubes Connect Colony in Soil with Wood in House
Typical Termite Entry Into Structures
1. Termites consume wood in ground
3. Finally infest wood2. Then construct tunnels
Mud Tubes
Wood Next to or Under Structure
Provides Food
Termites Access Into StructureFloating Slab
Termites Access Into StructurePartially Supported Slab
Termites Access Into Structure Supported Slab With Veneer
Termites Access Into StructureMonolithic Slab With Veneer
Crack in foundation
Wood in contact with soil
Termites Access Into StructureWooden Porch
Termites Access Into StructureDirt-Filled Porch
Foundation Penetrations
Concrete shrinkage allows termites access
Foraging and Guidelines
• Guidelines preferred
• When unconstrained, termites will tunnel in a radiating pattern
• When guidelines are introduced, the uniform tunneling pattern is disrupted and direction proceeds along guidelines
Foraging and Guidelines
Day 14 Day 14 (Found Gap 3d)
What Are Guidelines?
Construction Mistakes and Homeowner Alterations Allow
Termite Access
Exterior Finish Below Grade
Allows Termites Hidden Access
Hidden Termite Access
• Monolithic slab
• Vapor barrier used as form
• Brick veneer and stucco extending below ground
Hidden Termite Access
Subterranean Termite Entry Points
• Foundation– Cracks– Plumbing connections– Expansion joints– Utility conduits– Non-integral footers
(Cold joints)
•Exterior Siding–Stucco–Brick veneer–Wood, vinyl,
Hardy Board–EIFS
New Colony: What Makes an Area Attractive?
Moisture Next to Foundation
• Gutters and downspouts
• Improper drainage, grading
• Sprinklers, irrigation, water spigots
• Roof leaks
Gutters
• New Building Code– Gutters and down
spouts on eaves under 6” wide
Water can build-up next to foundation due to lack of gutters
Mis-directed downspouts
Sprinkler head directs water towards bushes
Roof
gravity
Improper Roof Flashing
No flashing
Not effective•Allows moisture buildup
•In wall voids•Adjacent to foundation
Walls Voids
Summary of Key Concepts• Food
– Wood-to-soil contact
– Form boards not removed
– Wooden debris left inside CMUs
– Wood refuse buried under slab
• Water– Improper drainage, grading
– Irrigation wets foundation
• Access– Exterior cladding, EIFS below grade
– Landscaping
– Plumbing penetrations
– Additions, adjacent slabs
Why Pre-Construction Treatments Fail
• Pre-construction disruption– Additional grading, vapor barrier, walking across treated area
• Contractor error– Grade stakes, form boards, cellulose debris within foundation
• Post-construction disruption– Landscaping or add-ons
• Breakdown due to climate and soil conditions• Applicator error
Infestation Rates in St. John’s County
27
6.7
0
5
10
15
20
25
30
Old Code Termite Code
Perc
ent I
nfes
ted
X2 = 120.533, df = 2, P = 0.001
Author: Dina Richman, University of [email protected]
Photos: Dina Richman and Cynthia Tucker, University of Florida
Entomology And Nematology Department Copyright University of Florida 2000
For more detailed information see the Featured Creatures WWW site at
http://creatures.ifas.ufl.edu/