Loss of Pole Strength due to Decay:

Core decay in the early life of the pole has limited effect on pole's strength, as the major mechanical stresses are at their highest in the outer sapwood section at the ground line section of the pole. This is unfortunately also the part of the pole that is most vulnerable to decay and termite attack in service.

Thus, it can be seen that any loss of strength in the outer layer of the pole at the ground line can have a significant effect on the pole's strength and its resistance to in-service loads, due to bad weather and ice loading etc.

Poles that break in bad weather, will often, on inspection, look acceptable to the untrained eye, yet on closer examination, it can be seen that failure has occurred as a result of low level decay in the outer section of the pole around the ground line section leading to a loss of strength.

Wood Pole Failure due to Termite Attack:

Wood preservative treatments are highly effective at preventing termite attack of treated wood. This protection from attack is effective, as long as the concentration of wood preservative in the pole remains at a suitable level.

As a general rule, where wood that has a high moisture content and low or no preservative protection, it is vulnerable to decay or decaying.

In preservative treated wood, loss of the preservative over time due to oxidation and leaching from the wood, means there is generally a direct correlation between the conditions for wood decay to occur and the conditions for termite attack.

Another factor that can lead to termite attack is cracks that form above and below ground through to the core of the pole allowing termites to access the unprotected core of the pole. Wood has a much greater tendency to crack around or above the ground line section of the pole, due to drying and changes in moisture content and weathering over time. The formation of cracks in this section of the pole can allow termites to access the damp unprotected core of the pole. Deeper in the ground, moisture level in the wood tends to remain constant, normally limiting both cracking in service and termite access to the unprotected core of the pole.