Subterranean Termite Damage to Pressure Treated Fence
Pressure Treated Wood After 6 Years

Cross section of pressure treated fence post after 6 years. Subterranean termite damage is extensive.

At Thrasher Termite & Pest Control, we pull out a lot of subterranean termite damage from homes, but frankly we were surprised by the amount of subterranean termite damage found in this six-year-old pressure treated fence post.  After all, isn’t pressure treated wood supposed to be resistant to termites?

How long does pressure treated wood last?

Clearly not as long as you think!

Pressure-treated lumber is wood that has been immersed in a liquid preservative and placed in a pressure chamber. Pressure forces the chemical into the wood fibers. Pressure treated wood is classified by expected product performance for a particular use–the Use Category System (UCS). Wood recommended for fence posts is rated UC4A or UC4B. This rating us usually found on a little tag stapled to the end of the piece of lumber.

The installer of this fence used UC4A lumber–the recommended choice for treated wood used in contact with the ground. So then, how did subterranean termites do so much damage in such a relatively short time?

1. The piece of lumber may have been mislabeled.

2. The producer of this piece of lumber may have done a shoddy job of pressure treatment.

3. Six-years might be the life-span of UC4A pressure treated wood exposed to subterranean termites.

Don’t rely on pressure treatment to protect your fence from termites. The best way to ensure your fence is not destroyed by subterranean termites is to eliminate wood to soil contact. Subterranean termite colonies live in the ground. Worker termites cannot last long outside of their soil or wood tunnels. Keep wood away from the soil to thwart subterranean termites. Attach fence posts to concrete piers set above the soil surface. Keep soil, leaves, and mulch away from fence posts and the base of the fence.

This advice will keep subterranean termites away from your house: keep soil, leaves, and mulch below the concrete footer of your house, and definitely away from any wood siding. Do not attach wood fences or gates to your house. Every three years, order a complete termite inspection of your home from a licensed pest control company such as Thrasher Termite & Pest Control.

Properly installed fence

A properly installed fence has no wood to soil contact. This fence post is installed in concrete above grade. The footer boards are also above the soil surface. Subterranean termites have no easy path to the wood. Although this wood is pressure treated, the installation method is the most important reason that this 15-year-old fence has not become a feast for subterranean termites.


Thrasher Pest ID

Text pest photos to 408-354-9944
The better the photo, the better the identification!


  1. […] How Long Does Pressure Treated Wood Last? […]

  2. This is going to be an eye-opener for people who purchased treated wood and feel that they don’t need to undergo termite control. Soil contact will always make wood vulnerable to termite attacks as the constant exposure to moisture can soften the wood. Great tips for keeping fences safe against termites, thanks for sharing.

Share This!

More Posts You May Find Interesting