The Pest Problem
Nobody Talks About

Termites cause an estimated $5–6 billion in property damage annually in the United States, according to the National Pest Management Association. This figure represents a recurring, predictable cost — not a natural disaster or rare event, but the expected outcome of building residential structures from organic materials in a country where wood-destroying insects are present in every state except Alaska. The industry's response has not been to change the materials. It has been to spray the ground beneath the home with pesticides and renew the contract every several years. The occupant, and the surrounding environment, absorbs both the pest damage when it occurs and the chemical treatment applied to prevent it.

Why Standard Construction Is a Termite Invitation

Subterranean termites — the species responsible for the majority of structural damage in the United States — feed on cellulose, the primary structural polymer in wood. Standard residential construction is composed largely of cellulose: dimensional lumber, OSB sheathing, engineered wood I-joists, plywood, particle board, and MDF. From a termite's perspective, a standard-grade American home is not an obstacle. It is a food source.

Why Engineered Wood Makes It Worse

The shift from solid dimensional lumber to engineered wood products that has defined American construction since the 1980s has consequences for pest vulnerability that parallel its consequences for moisture performance. The same manufacturing process that creates the moisture problems described in Part 1 of this series also creates increased termite vulnerability.

When wood is ground into strands (OSB), sliced into veneers (plywood), or shredded into fibers (particle board and MDF), the protective lignin structure and natural extractives found in solid wood heartwood are disrupted. The dramatically increased cellulose surface area — a single sheet of OSB has enormously more exposed cellulose than a comparable dimensional lumber board — gives termites direct access to fiber that would have been protected in solid timber. The adhesive resins that bind engineered wood products together do not deter termite feeding. In some engineered wood products, researchers have documented faster termite penetration than in comparable solid wood specimens.

The Moisture-Pest Compounding Effect

Moisture damage and pest vulnerability interact in a particularly damaging way in standard construction. Subterranean termites are attracted to moisture — they require it to maintain colony hydration and prefer wood with elevated moisture content. Moisture-damaged OSB and engineered lumber, as described in Part 1, becomes not only structurally compromised but also more accessible and attractive to termite colonies. Fungal pre-digestion of cellulose in mold-affected wood further reduces the mechanical resistance that makes undamaged wood harder for insects to penetrate.

The cascade: a slow roof or window leak saturates OSB sheathing → the moisture-damaged wood develops mold colonization → fungal activity softens the cellulose structure → termites targeting moisture-elevated wood find compromised, pre-softened substrate → the damage extends deeper and faster than it would in undamaged wood → structural compromise is discovered only during renovation, years later, by which point replacement of multiple structural components is required.

The Chemical Treatment Stack Beneath Your Home

Standard pest management for residential construction in termite-active regions operates on multiple layers: soil treatment at construction, wood treatment during manufacturing and framing, and ongoing baiting or perimeter treatment systems as part of the annual bond renewal. Each layer represents a chemical application in proximity to the home's occupied spaces.

Soil Termiticides: What's Under the Slab

The most significant chemical application in standard residential pest management is the soil termiticide layer applied beneath and around the foundation during construction. This treatment creates a chemical barrier intended to kill termites that enter from the soil before they reach structural wood. The chemicals used are not benign.

Fipronil (marketed as Termidor) is the most widely used residential soil termiticide in the United States. It is a broad-spectrum phenylpyrazole insecticide classified by the EPA as a possible human carcinogen (Group C). Research has documented significant environmental persistence — fipronil and its degradation products remain active in soil for years after application. Fipronil is highly toxic to aquatic invertebrates and has documented impacts on non-target insects including bees at sub-lethal concentrations. Studies have detected fipronil runoff in urban waterways adjacent to treated residential areas at concentrations above aquatic toxicity thresholds.

Imidacloprid, a neonicotinoid used in some termite management and lawn treatment programs, is under ongoing EPA review for pollinator impacts. The class-level concern with neonicotinoids — documented interference with bee neurological function at environmentally relevant concentrations — applies to residential soil applications that allow the compound to reach flowering plants and groundwater through normal water movement.

From an indoor air quality perspective, the most relevant concern is vapor intrusion — the migration of volatile compounds from soil-applied pesticides into the living spaces of the home above. Homes with slab construction are particularly susceptible if vapor barriers are incomplete or degraded. Research has documented detectable termiticide compound concentrations in indoor air above recently treated foundations, with concentrations declining over time but not reaching zero for months after application. Given the 5–10 year efficacy window of most soil treatments — after which re-treatment is standard practice — this is not a one-time exposure event.

The Borate Wood Treatment Layer

Many standard-grade framing packages include borate treatment of structural lumber — a pesticide and fungicide application that reduces termite feeding and mold colonization. Borate compounds have lower acute toxicity profiles than synthetic pyrethroids and neonicotinoids, and their use represents a genuine improvement over no treatment for organic substrates that require chemical support.

The limitation is identical to borate mold inhibitors described in Part 2: the treatment layer is applied to an inherently organic substrate that it cannot fundamentally protect. Borate-treated wood is still organic wood with full cellulose accessibility once the surface treatment is penetrated or degraded by moisture. It is still a mold substrate and termite food source — the treatment shifts the probability curve, it does not change the material's fundamental character. And the treatment itself represents a persistent chemical additive in the home's structural fabric.

CCA: The Legacy Contamination Already in Millions of Homes

For homeowners in homes built before 2004, a specific and more acute chemical concern may already be present in the structure: chromated copper arsenate (CCA)-treated lumber. CCA was the dominant pressure treatment for residential outdoor and ground-contact wood from the 1970s through the voluntary industry phase-out that took effect December 31, 2003.

What CCA Is and Where It Was Used

Chromated copper arsenate forces arsenic, chromium, and copper into wood fiber under pressure, producing a green-tinted lumber that became the standard specification for decks, play structures, fence posts, crawl space framing, and any wood requiring ground contact or moisture resistance. Arsenic is a Group 1 human carcinogen — the World Health Organization's highest classification, indicating established causation of cancer in humans. Chromium VI compounds are classified as respiratory carcinogens.

The voluntary phase-out in 2003 was not a recall or regulatory ban. Homes built before 2004 that used CCA lumber — in decks, play structures, stair stringers, crawl space framing, or exterior trim — still contain that lumber. It has not been removed. The arsenic leaching continues.

The Documented Exposure Pathways

Research on CCA-treated wood surfaces has documented measurable arsenic transfer to the hands of people who touched treated surfaces, even without deliberate contact with soil or debris. Studies measured arsenic hand loading on children after playing on CCA-treated play structures, finding concentrations that, combined with hand-to-mouth transfer rates in young children, produced daily arsenic intakes above EPA reference doses in some scenarios. Soil samples adjacent to CCA-treated deck structures showed elevated arsenic concentrations that persisted for years, creating ongoing exposure risk for children playing in yard areas.

CCA-treated wood can be identified by its greenish tint in older lumber, though weathering dulls this characteristic over time. Test kits are available through hardware retailers that detect arsenic presence on wood surfaces. For homes with outdoor structures built before 2004, testing before allowing children to use adjacent areas is a straightforward and low-cost protective measure.

The Compounding Cascade: When Moisture Damage Meets Pest Damage

Parts 1 through 4 of this series describe what appear to be separate failure categories — moisture, chemical exposure, fire, and pests. In practice, these failures compound each other through the same underlying material vulnerability. Understanding the cascade explains why standard construction's problems tend to present in clusters rather than in isolation.

The Full Failure Sequence

A representative scenario in a standard-grade home in a termite-active warm-climate region might unfold as follows. A slow roof leak — a common event over any 10–15 year period — saturates the OSB roof sheathing and wall framing behind the exterior cladding. The wet OSB swells and begins mold colonization within 48 hours, per EPA guidance. Formaldehyde emissions from the moisture-activated particle board and engineered wood components increase. The moisture-elevated wood and its fungal pre-processing makes the framing cavity more attractive to the subterranean termite colony already present in the soil below the foundation. Termite activity extends through the moisture-damaged zone. Structural compromise develops in floor system I-joists and wall framing OSB. Occupants develop respiratory symptoms from mold spore exposure — attributed to seasonal allergies. Three to five years after the initial leak, during a bathroom renovation, the contractor discovers extensive mold-and-termite damage requiring replacement of a significant portion of the framing, subfloor, and sheathing.

Each individual failure — the leak, the mold colonization, the pest activity — was predictable from the material specifications. Each was the expected performance of standard construction materials under conditions that standard construction guarantees over a normal ownership period.

The Domus Alternative: Materials Termites Cannot Eat

The pest problem, like the moisture and fire problems documented earlier in this series, has an engineering solution that doesn't require ongoing chemical management. Materials without cellulose provide no food source for wood-destroying insects. This is not a nuanced tradeoff — it is a compositional fact. Termites do not eat steel. They do not eat magnesium oxide. They do not eat concrete or masonry. They do not eat fiber cement.

Cold-Formed Steel Framing

Steel framing eliminates the pest vulnerability that requires chemical management in organic construction — not by treating steel against insects, but because there is no mechanism by which insects can damage steel framing. There is no cellulose to consume, no moisture-absorption pathway that compromises structural integrity, no food source that termites, carpenter ants, or wood-boring beetles can exploit. A steel-framed home in Miami or Houston requires no soil termiticide treatment, no annual bond inspection, no wood treatment, and no re-treatment cycle. The pest management cost — including the chemical exposure cost it represents — is eliminated by material selection, not managed by ongoing chemical application.

MgO Board and Inorganic Sheathing

Magnesium oxide board sheathing, as the OSB replacement specified by the Salus Standard, eliminates the sheathing layer's contribution to pest vulnerability. Where OSB provides an organic substrate that termites can colonize and moisture damage makes increasingly accessible, MgO board provides zero food value to insects. Combined with steel framing, it creates a structural envelope with no organic components that wood-destroying organisms can exploit.

Naturally Pest-Resistant Wood Where Wood Is Specified

The Domus Salus approach to wood is specific: standard framing lumber fails the Salus Standard due to moisture vulnerability, pest susceptibility, and chemical treatment requirements. However, the Salus Standard permits the use of naturally pest-resistant wood species — redwood heartwood, cedar heartwood, and cypress heartwood — in applications where wood is selected for architectural effect or where its natural performance characteristics make it appropriate.

These species accumulate extractives in their heartwood — tannins, oils, and other compounds — that are naturally toxic to termites and decay fungi. Redwood heartwood has been documented to resist termite and decay damage for decades without treatment in direct soil contact applications. These species achieve pest resistance through their composition, not through chemical impregnation — the same principle that distinguishes Salus-approved structural materials from standard-grade alternatives.

The distinction matters: cedar decking on a steel-framed home, specified for its aesthetic character and installed with appropriate clearance from soil, represents a different material decision than OSB sheathing on a wood-framed home with soil termiticide and borate treatment. The former leverages natural material performance. The latter substitutes chemical treatment for adequate material selection.

Due Diligence: What to Ask and What to Look For