According to a study from the Western Wood Preservers Institute the expected life of wood utility poles can be conservatively estimated at 75 years or more when they are properly inspected and maintained. Interestingly, most utility companies estimate the serviceable life span of a pole to be only 35+/- years.
Wood Utility Pole Treatments
Utility poles are usually treated with either pentachlorophenol, chromated copper arsenate, copper napthenate, or creosote. Whichever preservative treatment is used, the main goal of the treatment is to extend the life of the pole by rendering the wood useless as a food source for termites and other wood boring pests and to reduce the effects of decay caused by rot and decay. All of the treatments listed above provide excellent life spans for poles. They are usually chosen based on factors including climate where the poles will be installed, environmental impacts of the chemicals used, concerns around how the poles will be handled, and even individuals’ preferences.
The Biggest Problems for Wood Utility Poles
Most decay of wood utility poles happens at the ground line where the poles are often in contact with moisture which causes rot and decay. Wood utility poles do not have many other natural enemies other than the occasional fire, woodpecker, or car wreck. Wood utility poles are quite resilient and can withstand many natural conditions including high winds, acidic soils, and salty air – conditions steel and concrete poles may not withstand as well.
Increasing the Life of Wood Utility Poles
Properly treated wood utility poles are nearly guaranteed to last about 35 years without any inspections, maintenance, or preventative measures. However, the life span of utility poles can be drastically increased (easily doubled) through a regimen of periodic inspections and maintenance such as pole wrapping, which requires digging around the pole and literally wrapping the pole with a protective barrier. An excellent preventative measure is to coat the pole with the polymer wood coating from American Pole and Timber. The polymer coating must be applied before the pole is installed but provides a protective barrier that will prevent the need for labor intensive pole-wrapping in the future.
The study I mentioned at the beginning of this report actually suggests that utility poles can last more than 135 years (up to 260 years – yes, two, six, zero) but that over time other “degradation mechanisms” take their tolls. Typical maintenance programs are not geared towards correcting those issues which include pole top decay, pole splitting, decay at connections, and excessive weathering so the reasonable estimate of a wood utility pole should probably remain in the neighborhood of 75 years.
Applying Your New Knowledge of Wood Pole Life Spans
There is a great chance you are not in the utility business and just want to know how long your barn poles will last.? While there are no hard numbers on that – at least not that I have found YET – this study reveals that the life is probably longer than you might have even hoped.? Barn poles, fence posts, and small electric poles are treated with the same chemicals as utility poles and usually to the same retention levels using the same methods.? Though utility poles are held to higher standings of structural grading and specifications than your average barn pole you can probably expect the life spans to be similar. Again, the extended life span requires some periodic checks and maintenance.
If you are using treated poles or pilings around a marine environment, the rules are a little different since the surroundings are wetter and generally more dynamic and harsh (waves, changing tides, different organisms, constant contact with water).? Properly treated poles or pilings for freshwater applications can probably be made to last 30 years with proper preventative measures and maintenance.
Here’s some solid logic.? Think of all those old barns and fences that were built by your grandfather’s grandfather practically forever ago. While “they don’t make ’em like they used to”, the treatments have improved.? You can expect your treated wood poles to last a lifetime.