The Importance of Anchoring Rooftop Equipment in an Earthquake
04/14/2023
Make Resilient Upgrades | Strengthen Your Home • Earthquakes
Why does it matter?
Equipment such as heating, air conditioning, satellite dishes, or solar collectors mounted on the roof of a home or other elevated areas pose a risk during an earthquake due to their weight and mass. Preventing these elements from breaking loose can avoid damage and injury, and also help with recovery after an earthquake as these systems can remain operational. Additionally, anchoring these items makes them more resistant to high winds.
What do I need to know?
- Improperly or unanchored mechanical equipment can slide, tilt, overturn, or fall.
- These items may be damaged by shaking, or they may be crushed by other fallen components.
- Failed large mechanical equipment may fall or otherwise damage structural elements.
- While vibration isolation is used to ensure the proper day-to-day operation of equipment in preventing vibrations, this equipment is particularly vulnerable to earthquake damage. Standard springs used for isolation do not have adequate capacity to resist shear and uplift forces.
Where do I start?
- Although a general rule of thumb is to anchor larger equipment, its a best practice to securely anchor ALL items attached to rooftops or other locations where they can become dislodged and cause other problems.
- Look for equipment that has been shake table tested and is rated for seismic loading.
- Ask about seismic load ratings and seismic anchorage details when you purchase any new equipment such as air conditioning units.
- Ensure connections of fuel lines, electrical lines, optical cable, piping, or ductwork are correctly secured to avoid damage.
- Install flexible connections for fuel lines, piping, and electrical lines where they connect to rigidly mounted equipment.
- Elevated, ceiling-mounted, or rooftop units require special considerations. These units are typically mounted on curbs or platforms to enhance waterproofing and flashing.
- Curbs upon which rooftop equipment is mounted may be custom-built on site or pre-manufactured. Seismic restraints for the curbs must include the connection between the equipment and the curb, and the attachment of the curb and the roof framing. Also, the curb must be sufficiently strong. If the equipment is internally isolated, increase the design forces for the anchorage appropriately.
- Many of these retrofits will require a licensed contractor to perform due to their complexity and access to hard-to-reach areas such as rooftops or ceilings.
- Install some means of bumpers or vendor-supplied restraints in systems with vibration dampeners.
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