The ANSI O5.1 document defines the size and class of wood poles.  The document stipulates the sizes of wood poles such that their average strengths meet set class loading values.  In other words, 50% of poles will be stronger than the class value and 50% of the poles will be weaker than the class value. 

ANSI O5.1 does not provide any information on the deflection of wood poles under class loads.  Deflection of poles becomes important in areas where mandated electrical clearances need to be maintained for safety.  PLS-CADD does provide deflection information when wood poles are subjected to loads.  However, those deflections are average deflections for that particular size and class of pole.  Since these are average values, additional margins need to be considered to ensure that safety clearances can be maintained.  Typically, this would be done by installing a larger pole than what is required for strength.

Like all manufactured poles, the strength and deflection of the EndruaPOLE is based on reliability-based design concepts.  In this concept, the 5% Lower Exclusion Limit (5% LEL) is used to class poles based on strength and deflection.  What does this mean?  By using the 5% LEL values, 95% of the time the EnduraPOLE will be stronger than its rated class load and 95% of the time the deflection of the EnduraPOLE will be less than the rated class deflection.

Thus, when selecting the EnduraPOLE, the pole will have the capacity to carry its design loads and more – ensuring system reliability under extreme weather events.  Also, its deflection will not encroach on any mandated safety clearances.  With the EnduraPOLE engineers will know how the pole will perform under the design loads rather than having to add margins to ensure that a wood pole will perform under its design loads.  With the EnduraPOLE™ engineers will sleep better at night.  Isn’t that what we all want?

Talk with an engineer about how EnduraPOLE deflection behavior aligns with your clearance and modeling assumptions.

While utilities often favor wood poles because they have the lowest material cost, materials such as concrete, steel, ductile iron and composite offer advantages in specialized applications. Each pole type responds differently to load, weather, and environmental exposure, which affects maintenance costs and long-term reliability. Understanding how composite vs. wood, concrete, steel and ductile iron utility poles behave over time in specific conditions can help utilities choose the right pole type for specific applications in their service area.

Wood Utility Poles: Widely Used with Long-Term Variability

Wood provides reasonable strength at installation. While it is the lowest cost option, changes in its strength can occur over time as it is exposed to environmental conditions. Decay due to natural biological exposure can occur in poles in wet and moist environments. Pests such as termites and wildlife such as woodpeckers can also attack wood poles causing them to deteriorate. Strength declines as the material deteriorates.

Wood utility poles require regularly scheduled inspection cycles, retreatment programs, and the risk of mid-life replacement. Wood remains widely used but creates a long-term maintenance load that is difficult to predict.

Concrete Utility Poles: Strong but Heavy

Concrete poles resist deflection and hold form under load, which appeals to many utility planners. However, their weight introduces challenges, and transporting them requires larger trucks. Placement also often requires heavier equipment. Cracking can occur from impact or freeze-thaw cycles. Once a crack forms, water can intrude into the pole and cause deterioration and corrosion of the steel reinforcements. This could severely reduce the strength capacity of the pole.

In many corridors, the weight of concrete utility poles poses limits to where crews can install them. Difficult access increases costs and slows outage restoration.

Steel Utility Poles: High Strength with Corrosion Exposure

Steel is structurally strong, but corrosion is a common concern as salt air, corrosive soil conditions, and coating wear influence how the pole performs as it ages.

For utilities managing these assets, steel demands ongoing coating verification and corrosion monitoring. These tasks add operational costs over the life of the structure.

Ductile Iron Utility Poles: High Strength with Corrosion Exposure

Ductile iron is structurally strong, typically ductile iron poles in normal atmospheric environments develop a protective patina when exposed to the environment.  However, corrosion is also a concern in corrosive environments as salt air and corrosive soil conditions.  Ductile iron poles are also heavier than steel poles.

For utilities managing these assets, ductile iron requires ongoing coating verification and corrosion monitoring. These tasks add operational costs over the life of the structure.

Composite Utility Poles: Consistent and Inert Material Behavior

Fiber-Reinforced Polymer (FRP) poles, or composite poles, are typically produced through a pultrusion process or a filament winding process. The material is very stable over the long term. FRP poles do not rot, rust, absorb moisture, or deteriorate. Environmental exposure has limited impacts on its mechanical properties.  Strength and deflection remain steady across decades of service. 

Their stability in harsh conditions reduces operational costs. Inspections can be performed over longer intervals than other pole types and the focus of the inspections can be less than other materials.  Typical inspections of FRP poles will be to verify that no external mechanical damage has occurred and that the surface resin of the pole is performing well.   Composite utility poles’ consistent, reliable performance contributes to their growing popularity among utilities installing new, retrofitting, or replacing poles.

Composite vs. Wood, Concrete, Steel and Ductile Iron Utility Poles: Installation and Maintenance Considerations

Weight and Access

Wood weight varies by species and moisture content.  Concrete utility poles require significant lift capability. Steel poles need boom access and careful handling. Ductile iron poles are heavier than steel poles and also require boom access and careful handling.  Composite poles weigh less per foot than all four and can be moved with smaller equipment. Their lighter weight allows crews to safely reach more locations with fewer constraints.

Handling Requirements

Composite utility poles only require padded forks or nylon slings to protect the outer layer during handling. Concrete poles are heavy and can suffer impact damage due to rough handling.  Steel poles require careful handling to minimize damage to the protective galvanizing or painted protective coatings. Ductile iron poles are heavy and may require heavier equipment.  Wood utility poles tolerate rough handling but require follow-up inspection over time. Each pole type’s handling requirements influence crew time and risk of damage.

Safety

Composite utility poles reduce electrical risk because they remain non-conductive in typical conditions, unlike steel, ductile iron and wood or concrete when wet. They also don’t require chemical treatments like wood poles, lowering exposure concerns for crews. Each material behaves differently in the field. Composite poles deliver safety advantages for crews during installation and routine maintenance work.

Composite vs. Wood, Concrete, Steel and Ductile Iron Utility Poles: Environmental Condition Considerations

Wildfire Exposure

Composite utility poles provide fire resistance and are self-extinguishing when exposed to wildfires. Wood poles can ignite and contribute fuel to a fire. Concrete poles will not ignite however, they can crack or spall under thermal stress, which could result in a permanent reduction in strength.

Steel and ductile iron poles will not ignite, however they can lose strength at elevated temperatures, which could cause them to yield or fail. Also, when steel and ductile iron is exposed to high temperatures and cooled, the metallurgical properties of material could change, causing poles to become brittle and be susceptible to brittle fracture. The high heat of wildfires could melt the galvanized coating or destroy any coatings on steel poles, leaving them susceptible to long-term corrosion.

The self-extinguishing properties of composite poles keep damage to the poles to a minimum after exposure to wildfires. Composite poles can experience heat-related softening if temperatures rise high enough. However, since they are designed with residual strength, they will continue to keep the lines in the air after a wildfire. Each material responds differently in wildfire conditions, and composites lessen several of the fire-related vulnerabilities that lead to pole failure in major events.

Coastal or Corrosive Environments

Composite utility poles perform well in coastal and corrosive environments. Wood can soften or decay as it cycles through wet conditions.  Steel requires continuous coating maintenance to slow corrosion. Ductile iron poles should not be used in coastal or corrosive environments.  Concrete can experience spalling when chlorides reach the reinforcing steel. Each material responds differently to salt and humidity, but composite poles offer stable performance with fewer maintenance demands in these locations.

What Utility Teams Should Take Away

There is no pole material type which is best for all situations. Each has its advantages and disadvantages. Pole materials behave differently under real field conditions, affecting their life cycle cost, utility crew workload, and long-term reliability. When assets age or corridors face complex environmental demands, predictable behavior becomes a critical advantage.

While composite poles are not the best pole material for all applications, they are the best pole material for a broad range of applications as they offer consistency that simplifies planning, reduces unknowns, and supports grid-hardening objectives.

If you are evaluating how fiberglass composite poles fit into your system plan, our engineers can review your corridor needs and help model performance. We support load analysis, environmental assessments, and installation planning. Bring your most challenging terrain or access constraint, and speak with an engineer. You can request design support, specification packages, or a technical review to understand how EnduraPOLE™ contributes to long-term grid resilience.