Borates applied to wood framing (above) provide one of the most
effective treatments against the super-aggressive Formosan termite.
Pretreated lumber is available, but typically a pest-control
specialist must spray all the framing and sheathing with a borate
solution at the "dried-in" stage of construction.
To build a home that will solidly rebuff nature, builders and
remodelers in the southeastern U.S. have their share of
adversaries. A potent mix of tropical storms and excessive moisture
is bad enough, but it's ruinous insects that account for the most
consistent source of home damage. Year in, year out, the termite is
a king (and queen) of destruction, costing billions of dollars in
damages every year in the U.S.
Eradication of subterranean termites is nowhere in sight. In fact,
during the last 40 years, new, more aggressive termites have
increasingly invaded the U.S., requiring vigilant monitoring and
increased use of lethal deterrents. The Eastern subterranean
termite remains the most common pest, but since the 1960s, the
Formosan subterranean termite has become the more devastating and
difficult adversary. A typical colony of Formosan termites will
consume 100 times more wood per year than an Eastern subterranean
termite colony. This level of destruction can cause substantial
structural damage within a year. The Formosan variety is also able
to nest aboveground, rendering soil treatments ineffective.
And now there is yet a third termite species to contend with.
According to Dr. Nan-Yao Su, professor of entomology at the
University of Florida's Institute of Food and Agricultural
Sciences, a new Asian subterranean termite has arrived on Florida's
East Coast near Fort Lauderdale from Thailand and Malaysia by way
of Brazil and the West Indies. Dr. Su says it's too early to
speculate on how widespread a problem this new species will become,
but warns that it bears watching: It's as aggressive as the
Formosan and has the potential to become equally as
Subterranean termites are found from New England to the Gulf of
Mexico (insets), posing a significant threat to homes along coastal
waterways and just in from the shore, where damp clay and silt
soils provide prime conditions for termite survival.
While contractors are not exterminators, a knowledgeable builder or
remodeler still plays an important role in long-term termite
control. The ability to start the termite conversation and guide
clients toward the best method of protecting their homes is a
value-added skill that's increasingly vital to customer
satisfaction. Once the slab is poured and the walls are closed in,
the job of keeping termites out becomes harder.
First Line of Defense
Deterring termites starts with sound
building practice. Because termites primarily search for food by
the scent of rotten or decaying wood, it's important to remove
potential food sources from the job site to every extent possible
and to protect wood on the house from moisture:
• Do not bury stumps and wood debris on site, and keep cutoffs
and cardboard scrap out of the backfill.
• Remove wood concrete forms and stakes, and peel back the
ends of Sonotube forms from the tops of poured piers.
• Control runoff with gutters and downspouts, backfill with
well-draining material, provide good foundation drainage, and
control site drainage. These practices will keep soil drier,
robbing termites of the high soil moisture content they need for
• Use only pressure-treated wood in contact with the
• Be sure to hold siding and trim at least 8 inches above
Keep floor joists at least 18 inches above the soil in a
crawlspace. Most important, do not leave soil exposed beneath floor
structures; cover with poly, caulked or foamed to the
Porches, Decks, and Steps
Raise concrete footings for porches, decks, and steps out of the
soil to force termites out into the open, and keep wood at least 6
inches above the soil. Even better, build the latticework around a
porch or deck from a cellular PVC or other nonwood
Control strategies are twofold: (1) Keep wood
structures dry, and (2) eliminate entry points where termites can
sneak into a building undetected from underground. It's extremely
difficult to block the entry points, as a termite can squeeze
itself through a 1/16-inch gap. The best control measures involve
designing structures that keep wood as far away from wet soil as
possible and eliminating underground entry points, as detailed in
the illustrations on this page and on page 4. At the very least,
these details will force termites to build their mud passageways
where they can be more easily detected.
Shields. The traditional method of
termite control has been the termite shield — sheet metal
installed at the top of piers or foundations. Termite shields won't
stop an infestation, though. When installed properly, they only
force termites to build passageways out in the open, around the
shield, where they can be detected.
Unfortunately, shields are very difficult to install properly.
Lengths should overlap and be caulked or soldered together, and any
penetration (around anchor bolts, for example) must be sealed as
Termiticides. The most common control
strategy for deterring subterranean termites has been termiticides.
Many argue this was easier with Chlordane and Heptachlor —
potent organochlorines that remained active for very long periods.
However, these chemical treatments were banned in 1988, and for
good reason: They are neurotoxins that readily leach into water
systems. When ingested, even trace amounts have been found to
disrupt central nervous functions and cause liver damage in
Never run stucco below grade. Instead, it should always terminate
at a weep screed held at least 4 inches above grade.
Modern organophosphates and synthetic pyrethroids — the most
common replacements for the more toxic organochlorines — pose
less of a threat to the community and are much less irritating to
applicators. However, they are still toxic to some species,
primarily fish, so their application is often restricted along
The biggest problem with post-Chlordane chemicals is that they are
far less persistent, so homes must be treated as often as every
five years. To be effective, there must be a continuous chemical
barrier in the soil surrounding a structure, which is easier said
than done. Treatment is best when applied during construction to
create a continuous horizontal barrier of treated soil beneath
slabs and vertical barriers through the backfill along foundation
walls and around piers. Post-construction treatment, while common,
is much less effective, and continual monitoring is critical.
A metal termite shield is simply a barrier to force termites into
the open. To be effective, all joints should be soldered and all
penetrations, such as anchor bolts, caulked.
The Borate Alternative
Treating the structural wood to rob termites of a food supply is
probably the most obvious method of home protection. It is
particularly effective against the Formosan termite, which may nest
aboveground. For interior residential use, borates are the new
standard. They have been used for 50 years in New Zealand, and
borate-treated lumber is now required in all new home construction
in Hawaii to combat the Formosan termite.
Though not poisonous to humans or animals, borates are a fatal
stomach poison to termites, inhibiting their ability to digest
cellulose. These chemicals are also effective against other pests,
such as carpenter ants and wood borers, and against fungi that
cause wood decay. Borates do not corrode hardware (unlike ACQ,
which is recommended for exterior use, but which accelerates the
corrosion of metal fasteners and hardware). However, borate-treated
wood is not recommended for exterior use or ground contact, since
constant wetting will leach it away from wood and decrease its
Borate-treated lumber. There are a few
methods to get the borates into and onto the wood. U.S. Borax, the
leading manufacturer of borate products in the U.S., distributes
Tim-bor for large-scale industrial use, and licenses the same
formula to Osmose Corp. (a leading manufacturer of ACQ- and
CCA-treated lumber, as well). Osmose Corp. markets borate-
treated dimensional under the Advance Guard brand name, which is
sold ready to use, fully treated like any pressure-treated wood
Treated OSB and other sheet goods, as well as trim stock and
moldings, are available.
Spray-applied borates. More commonly, untreated wood
is used for framing, and a pest-control specialist arrives with a
small crew at the dried-in stage and before drywall to treat the
job site in one evening. Tim-bor and and Bora-Care, both
distributed by Nisus Corp. (100 Nisus Dr., Rockford, TN 37853;
800-264-0870; www.nisuscorp.com), are the most common materials for
these spraying applications.
Borates penetrate wood well and, applied in suitable
concentrations, should be effective for at least 20 years.
Treatment at the job site requires that all wood/cellulose products
be sprayed, including all framing and flooring. The cost of borate
treatments averages $1 to $2 per square foot of floor space.
Borate applications are now available with warranties protecting
the homeowner against termite loss, making the treatment
competitive with traditional soil barriers, which have long come
A Better Barrier
One of the most promising new termite protections in recent years
is the Termimesh System. Developed in Australia and tested by U.S.
Dept. of Agriculture Forest Service in Gulfport, Miss., for over a
decade, Termimesh consists of a stainless-steel screen that is
installed at entry points.
Like metal shields, Termimesh installed beneath sill plates and at
the base of wall systems only prevents termites from entering a
building through hidden gaps. Termites may still build a passageway
around the barrier, but if installed correctly, this will force
termites to areas where their activity can be detected.
Like a metal shield, Termimesh can be installed at the base of
wall systems to prevent termites from entering a building through
hidden gaps. Unlike metal shields, Termimesh is easy to fold around
corners, and the stainless-steel screen can be bonded to concrete
with a cementitious bonding agent.
However, Termimesh offers a critical control that metal shields
can't provide: It's the only system that effectively seals the tiny
gaps in slabs, such as those around plumbing and conduit
penetrations. Termimesh flanges are sealed to pipes with
stainless-steel clamps, or laid beneath plumbing blockouts, then
embedded in concrete about halfway through the slab section, as
shown in the photos at left. Termimesh can be bonded using a
cementitious bonding agent that is painted over the mesh. This will
seal the screen to the masonry and concrete to create a barrier at
the base of veneer brick cladding.
For slab-on-grade foundations, Termimesh provides a barrier
around plumbing penetrations. When concrete cures, it may shrink
back from the pipe, allowing a tiny gap for termites to squeeze
through. The stainless-steel mesh can be secured to plumbing with
stainless-steel clamps (left) or installed beneath a foam blockout
According to Mike Boyd, vice president of Termimesh USA, which has
recently begun distributing the system from its headquarters in
Spring, Texas (Termimesh USA, 6046 FM 2920, Suite 506; Spring, TX
77379; 281-257-6558; www.termi-mesh.com), the screen material is far easier
to work with than metal flashing. It can be cut with scissors or
shears and folded. Corners are typically formed by folding, then
creasing the material with a small roller. The biggest drawback to
this system is the level of detail required for successful
installation. While termites may never be able to chew through the
mesh, they can crawl through the tiniest gap.
Currently, Termimesh offers detailed installation instructions and
specifications developed for the Australian market, but the system
has been evaluated and approved by the Southern Building Code
Congress International (NER 9713B).
For post-construction control, bait systems offer the most
promising alternative to spray-applied termiticides. Popular ones
include the Sentricon Colony Elimination System (Dow Elanco),
Firstline (FMC), and Exterra Termite Interception and Baiting
System (Ensystex). Of these, the Sentricon system (Dow
AgroSciences; 317-337-3000; www.dowagro.com/sentricon) is the most expensive, but
has the longest track record of success.
Most in-ground bait systems require periodic inspection of plastic
monitoring stations that are loaded with a tasty piece of wood.
There may be 20 to 30 monitoring stations around a home. When an
exterminator (professionally called a "pest-control operator," or
PCO) finds evidence of termite activity or feeding on this wood, he
will place a small amount of bait containing a termiticide.
Sentricon uses one gram of Hexaflumuron in each station. The
termites take the bait back to the colony, where the poison is
shared, wiping out the entire colony.
The Sentricon baiting system consists of plastic monitoring
stations holding baited wooden stakes. It's not uncommon to need 20
to 30 stations around a house, which then must be electronically
monitored. If termite activity is discovered, the stations are
loaded with termiticide that termites carry back to the colony to
wipe out the entire nest. While effective, this system may leave
the home unprotected until termites discover the
Most bait systems require brand-specific PCO training and
certification, which adds to the cost. While some do-it-yourself
bait systems are sold in home centers, there is very little
evidence that these are effective, and there have been some
complaints filed against makers claiming false advertising.
Bait systems are attractive for existing homes, particularly when
the homeowner no longer wants to rely on continuous applications of
toxic soil barriers. According to Dr. Michael Potter, an extension
entomologist at the University of Kentucky's College of
Agriculture, clients are usually relieved to learn that with a bait
system their carpeting won't have to be pulled back, their floors
drilled, or stored items moved.
However, critics of baiting systems argue that protection depends
on the termites being attracted to the monitoring stations. As a
result, it may take a long time for termites to actually swallow
the bait, which leaves the structure unnecessarily at risk.
Moreover, bait systems require ongoing monitoring. Michael Potter
urges that baiting systems be sold as programs, for which the
client pays an on-going subscription. "Failure to maintain the
annual service agreement is a prescription for disaster with
baits," notes Potter. "There is no residual pesticide left in the
soil after the termites have been eliminated, so ongoing protection
depends upon diligent monitoring." ~
Mitch Buroker writes on science and technology from New York City
and Trumbull, Conn.