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Occupied Roofs

Roof-top gardens, terraces and recreation areas are a desirable feature on many tall structures. However, these occupied roof areas are often located at the top or perimeter of a building and are therefore likely candidates for direct lightning strikes.

Rooftop gardens at this hospital provide a place of respite to patients, visitors, and staff. Handrails, parapet caps, and a shade structure were designed to be part of the lightning protection system without adding visual distractions. (Photo: Mercy Medical Center, Baltimore)

Lightning Protection Systems on Occupied Roofs

Special Risks and Unique Design Opportunities

Rooftop decks, terraces, and gardens that will be visited by building occupants are classified in the International Building Codes as “occupied roofs.” Occupied roofs are at high risk of being attachment points of lightning strikes because they are located at the top and/or perimeter of buildings. More information about how to determine the locations on a structure where lightning is most likely to attach, visit our page on the  Rolling Sphere model.

Occupied and green roof areas offer designers limitless opportunities to make creative choices for the materials, function and aesthetics of the space.  The design of the lightning protection system for these locations is similarly open to ranging creative possibilities.  So long as designs adhere to just a few basic criteria, project planners are free to plan their rooftop spaces for maximum enjoyment and utility.

Lightning protection design considerations for occupied rooftops: 

Exposed components of a lightning protection system should be compatible with the terrace design, furnishings, and finishes.

 

Metal railings, wind breaks, and overhead structures are used as strike termination devices and substituted for exposed cables. (Credit: One Bennet Park)

Decorative cast bronze air terminals complement the limestone façade. Conductors are concealed inside the masonry and planters.  (Credit: Michael Chusid)

Exposed elements of the lightning protection system should be detailed to avoid distracting from views. In the photos below, the lightning rods have either been replaced by the metal railings or integrated so seamlessly that they are undetectable.

Solomon Cordwell Buenz /©Dave Burk

Photo: Belgravia Group

People in close contact with lightning protection systems may accidentally or deliberately damage exposed components of the system. Wherever possible, the air terminals, connectors and conductors should be designed and installed to minimize potential damage or displacement. 

The metal portions of the glass railing have been specially designed to perform as lightning protection.  Eliminating the need for air terminals and cables.

Associated Lightning Rod Company

Tall air terminals are run on the back of the glass to eliminate the need to attach to the glass or to run visible cable.

Warren Lightning Rod Company

Attention must be given to locating and detailing lightning protection cables, connections and through-roof penetrations so they will not interfere with the enjoyment of the terrace.

The lightning protection system may have to be coordinated with green roof areas. Rooftop trees, trellises and light poles can be integrated into the lightning protection system.

Kay Taylor/UVA Health System

Special Design and Installation Criteria

To seamlessly integrate the lightning protection with occupied roof designs, metal rooftop elements can be placed where the lightning air terminals would normally be located. These rooftop strike termination devices can be used in lieu of air terminals so long as they are permanent parts of the building and are constructed of metal that is at least 3/16 inch thick (0.064 inch thick for handrails) and is made electrically continuous with the lightning protection system. Railings, light posts, canopies and shade structures, decorative and sculptural items, and other metal fabrications can be used as strike termination devices if properly positioned.

Rooftop lightning protection for occupied roofs must still be part of a total building lightning protection system. All the lightning protection standards that apply to the complete structure must be observed.

For assurance that the lightning protection system is installed in compliance with recognized safety standards, specifications should require inspection and certification of the system by the Lightning Protection Institute – Inspection Program (LPI-IP).

Contact East Coast Lightning Equipment for further information regarding specifying lightning protection systems for occupied roofs. ECLE can also help you locate qualified lightning protection professionals, certified by the Lightning Protection Institute, to assist you with design and installation services.

Additional examples of creative lightning protection system integration can be found on our Sculpture & Custom Decorative page.

Case Studies

Does your building require lightning protection?

To Learn More About Lightning Protection for Occupied Roofs Visit 

Related Articles

  • Rooftop Terraces

    Rooftop Terraces

    Building Enclosure, Case studies of the lightning protection systems on five highrise buildings with rooftop decks or terraces.

Related PDF

  • “Standing Ready: Lightning Protection for Hospital Rooftop Gardens, Terraces.”

    “Standing Ready: Lightning Protection for Hospital Rooftop Gardens, Terraces.”

    Medical Construction & Design

Final Word

Lightning protection systems prevent damage to the building structure, contents, and occupants. They do not, however, provide protection to individuals on an occupied roof during an electrical storm. The building owner and occupants must be warned, “When Thunder Roars, Go Indoors.”

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