Flagpole safety in Mexico: wind, hurricanes, lightning and liability

A flagpole is a slender structure that carries at its top a cloth the wind pushes without rest. In Mexico, where the coasts are hit by hurricanes every season and thunderstorms are frequent in summer, the safety of a flagpole depends on its design, its foundation and its maintenance. This guide brings together the rules and references involved.

Wind and structural design

The wind load on a flagpole grows with its height and with the size of the flag. The Manual of Civil Works Design of the Federal Electricity Commission, in its chapter on wind design (2020 edition), sets regional wind speeds by zone of the country, which serve as the basis for structural calculation. Makers of large poles design the pole and its foundation for the local wind: Grupo Symac offers the engineering and calculation of its poles, and Astabanderas de México states that its aluminium poles withstand wind speeds of more than 200 km/h, according to its data.

The flag is the most exposed part. According to Forbes México, the monumental flag at the San Jerónimo roundabout in Mexico City tore in its centre in the strong winds and rains of the season, even though it was made of ripstop nylon, a tear-resistant fabric.

Hurricanes and alerts

The coasts of the Gulf of Mexico, the Caribbean and the Pacific are exposed to tropical cyclones. The Early Warning System for Tropical Cyclones (SIAT-CT), coordinated by the National Civil Protection Coordination with information from the National Meteorological Service, alerts the public with five colours according to the threat: blue (minimal), green (low), yellow (moderate), orange (high) and red (maximum), both as the cyclone approaches and as it moves away.

The flag multiplies the area exposed to the wind: with the flag lowered, the load on the pole is much smaller and the cloth is not lost. The guide to flagpole maintenance covers inspection after a storm.

Lightning

A tall metal flagpole can be struck by lightning. Grupo Symac includes earthing with a lightning conductor among the installation stages of its aluminium poles. At workplaces, NOM-022-STPS-2015 regulates safety conditions for static electricity, including lightning protection systems. A specialist can assess the protection of each pole.

Work at height

Changing a rope, a pulley or a stuck flag at the top of a pole is work at height. At workplaces, NOM-009-STPS-2011, Safety conditions for work at height, applies to installation, maintenance, repair or cleaning at more than 1.80 metres above the reference level, and regulates the use of personal fall-arrest systems, scaffolding, lifting platforms and ladders. For monumental poles, assembly is done by crane, as Grupo Symac shows. The guide to flagpole repair covers this work.

Electricity

A flagpole with floodlights has an electrical installation, governed by NOM-001-SEDE-2012. Aluminium poles conduct electricity, and nearby power lines are a hazard during assembly. The guide to flag lighting covers the installation.

The owner’s liability

If a flagpole falls and causes damage, civil liability comes into play. The Federal Civil Code provides that anyone who causes damage to another by acting unlawfully or against good morals is obliged to repair it (article 1910), and makes the owner of a building liable for damage resulting from its total or partial collapse if this is due to a lack of necessary repairs or to construction defects (article 1931). The civil codes of the federal states, which govern matters between private parties, contain similar rules. Regular, documented maintenance reduces that risk; the guide to flagpole installation covers the foundation.