February 4, 2025
Imagine a fire erupting inside a high-rise building. Firefighters tackle the blaze, but danger lurks unseen. The inferno, instead of being contained, leaps from window to window on the exterior, bypassing internal fire safety measures. This is the chilling reality of the “leapfrog effect“.
WHAT IS THE LEAPFROG EFFECT?
The leapfrog effect describes a scenario where a fire spreads vertically up the façade of a high-rise building, bypassing floors in between. Here’s how it happens:
1. Fiery Breath :
An intense fire inside a building breaks windows, creating a furnace-like opening.
2. Heatwave :
Flames and scorching gases shoot upwards, engulfing the cladding (exterior material) above.
3. Ignition Highway :
Combustible cladding materials catch fire, creating a path for the inferno to travel.
4. Window Leap :
The intense heat shatters windows on floors above, igniting flammable items inside.
5. Repeat :
The cycle repeats, with the fire leaping from floor to floor, bypassing internal fire compartments and sprinkler systems.
6. Perimeter Void :
As critical as leapfrogging is, there is additional danger involving the perimeter void between the exterior curtain wall and floor intersection through which the fire can spread upwards. This spread of fire will be maximized due to the “chimney effect,” where once the oxygen in the air gap is utilized the fire seeks more oxygen and will move up rapidly.
REAL-LIFE NIGHTMARES
The leapfrog effect isn’t just a theoretical threat. Here are some real-world incidents that highlight its dangers:
Grenfell Tower Fire (London, 2017)
This tragic fire claimed 72 lives, partly due to the flammable cladding that facilitated the rapid vertical spread of flames.
Sharjah High-Rise Fire (UAE, 2012)
Faulty cladding materials were blamed for a fire that raced up a 30-story tower, injuring firefighters.
The Address Downtown Hotel (Dubai, 2015)
A fire erupted on New Years Eve, caused by an electrical short circuit, causing chaos, injuries, fatalities, and safety concerns. The intensity of fire spread was basically found to be maximized due to leapfrogging effect
PREVENTING THE LEAP
Building codes and regulations are being updated to address the leapfrog effect. This includes:
Fire-resistant Cladding: Using non combustible materials for building exteriors significantly reduces the risk of flames spreading.
Fire Breaks: Installing fire breaks along the façade can create barriers that impede the fire’s vertical movement.
Window Spandrels: Solid panels between windows (spandrels) can help prevent flames from directly reaching windows above.
Perimeter fire barrier systems: Different types of barriers are used to seal off the voids at the floor level to ensure fire compartmentalization. The correct use of cavity barriers should restrict fire in the air gap so that the only fire strain is from the outside, instead of both sides of the cladding.
By implementing these measures, we can prevent high-rise buildings from becoming infernos that leapfrog their way to the top.
