Subj: Do termites eat pressure - treated wood?
Date: 05/21/2000 11:03:27 AM Eastern Daylight Time
Do termites eat pressure - treated wood?
When I mention that wood decks should not be constructed on, near or below grade and that deck steps and posts should not have wood/soil contract. Owners, builders, clients and agents all look at me bewilderingly and say:
"This is treated wood, it can be close to, on or in the dirt. Termites won't eat this stuff."
For some unknown reasons most seem to have the impression that treated wood doesn't rot and that insects prefer another deli.
I guess they aren't aware. Termites eat pressure-treated wood. You saw it correctly, don't adjust your glasses. Termites attack chromium/copper/arsenic/treated southern yellow pine - you know that greenish-yellowish very heavy lumber used on decks and at masonry contact on foundations.
Numerous codes used throughout the United States clearly state that "pressure-treated and naturally resistant wood, such as heartwood or redwood and eastern red cedar, shall be considered as being termite resistant."
The key word is "resistant". They don't say impervious!
Here's what you as a Realtor and home owner should be aware of:
Termites will eat pressure-treated lumber if there is NOTHING else available close by. If it gets damp enough for long enough it will rot.
Field cut ends, rips, notches and drilled holes must be retreated in the field. (Right. When was the last time you saw a gallon of chemical available as a deck is being built or foundation plate cut or drilled? Did you or your contractor do this when you built your deck or house?)
The chemicals used to treat the wood will "leach" out over a period of seven-to-ten-years, leaving the wood vulnerable to other insects as well.
There are some insects and/or molds that thrive on chemicals and remove them, making the wood vulnerable to other pests, especially termites.
The outer 1-inch edge of boards, posts and poles seem to retain the chemical treatment and withstand the ravages of time. The centers however do not.
Here is the deal:
Our homes are situated in an area know for termite activity. Termites can do a substantial amount of damage to the wood structural components of a home. Extensive damage may be concealed. Several steps can be taken to reduce the risk of a termite problem. Conditions that are attractive to wood boring insects should be avoided. These conditions include the storage of wood in damp environments, wood/soil contact around the perimeter of the home (decking, siding, etc.), damp soils, leaky roofs, and unventilated spaces (roofs, garages, crawl spaces, etc.). Preventative chemical treatment, performed by a licensed pest control specialist, is also advisable.
The wood sills of structures and all lumber at near or below grade level should be avoided. Foundation walls should extend at least eight (8) inches above grade level (this includes landscape mulch and pine needles!). Steps and siding should be 6" above grade. The grade around the home should slope away 1" per foot ideally for at least 10 feet. These practices protect the floor and wall structures from moisture and allow for a visible area for detection of termite attack (you can see their tunnels).
Where the sills are found below grade, the grade level should be lowered, the foundation should be extended, or an effective moisture barrier should be provided.
What about treated post buried in the ground?
Buried post should be completely encapsulated below grade with concrete. Ideally, the concrete should extend 6" out from the surface of the post and 6" above grade. You should never see soil, mulch or pine needles touching the wood.
PS: It's not just the treated wood termites are eating? They also eat foam insulation board.
Termites are eating foam board products, both above and below grade. With many approved foundation waterproofing systems using foam board as protection to the "coating," and insulation used below slabs on grade, the builder is providing a ready food supply to termites (sort of like when the builders used to bury trash along the foundation and/or not remove wood forms around the footers, etc.).
It's this simple. Soil touching or near wood even if treated is unacceptable and must be avoided!
Portions of this article were taken from an article in the "ASHI Reporter" of May 2000 by Kurt F.
Kurt is an ASHI member and operates a Home & Building Inspection Service in
Millerport, Ohio. Designations include State Certified Building Inspector, State Certified Custom Applicator (Termite) and Chief Building Inspector, City of