The best architectural innovations stand the test of time, and parapet walls are high on the list. An excellent example of functional design adapted over time, parapets historically served as protective barriers on fortresses, allowing defenders to battle from behind the safety of the wall. Today, parapets still serve a protective purpose, guarding flat roofs against wind uplift, fire spread, and other hazards.
But modern parapets must also meet modern building codes, and roof engineers must contend with far more roof and wall assembly components than their medieval counterparts. Here, we’ll take a look at important considerations when using parapets in commercial construction, and how they were implemented at the impressive Fontainebleau Hotel Las Vegas.
Defining Parapet Walls
Parapet walls are an extension of a building’s perimeter walls above the roofline. The 2021 International Building Code (705.11) indicates that parapets must extend a minimum of 30 inches above the roof-wall connection, though this may not be sufficient in areas where foot traffic or user safety is a concern. For example, if parapets are intended to function as a guardrail system, OSHA fall protection guidelines [1926.502(b)] require a height of 39 to 45 inches. With minimum height guidelines in mind, parapets can extend 5, 10, or even 20 feet above the roofline depending on design needs in various situations.
Wind Uplift
The edges and corners of roofs are the most susceptible to wind uplift, which can cause severe damage if not planned for and prevented. This is especially true in areas prone to high winds, including high rises. A well-designed parapet wall can help mitigate these forces by acting as a barrier and reducing wind speed and pressure at the roof’s edges. While 30 inches is the minimum parapet height, many roof engineers have adopted 36 inches as a standard height to increase the benefits of wind uplift prevention, including securing the roofing system and preventing failures.
Having said this, because parapets are exposed to wind from both sides, they can experience high wind pressures themselves. Engineers should refer to ASCE 7-16 for direction on applying wind load calculations in both roof and parapet design. This section also provides guidance on the types of materials and fastening requirements needed for successful parapet construction. Fasteners must be selected based on the calculated design wind pressure (which varies depending on the height, location, and exposure of the building), and spaced appropriately to distribute loads evenly for wind uplift resistance.
Fire Prevention
Parapet walls are crucial in helping to prevent the spread of fire between the face of a building and the roof, or between adjacent buildings. By extending above the roofline, parapets can slow down or stop the spread of flames from one building to another and prevent the roof system from becoming part of the fire.
Fire codes including NFPA 221 indicate that parapet walls must meet specific configuration and material standards to act as effective fire barriers. Commonly, parapet walls must use gypsum board, concrete, masonry, or steel in order to qualify for fire-rated roof assemblies. Additionally, IBC 705.11 outlines that parapets must have the same fire-resistance rating as the supporting wall and must have non-combustible materials for the uppermost 18 inches of the interior (roof-side) of the assembly.
Fire prevention also plays into parapet height. IBC 705.11 dictates that, on roofs that slope toward the parapet on a 2:12 slope or greater, the parapet must extend to the same height as any portion of the roof within a fire separation distance where protection of wall openings is required.
Water Management
In instances where parapets are used around the entire perimeter, designers must pay particular attention to moisture management. In this “fishbowl” effect, heavy rains or a backed-up drain could cause water to collect without careful consideration. Drainage cutouts in the parapets can help mitigate this issue, which could become more prevalent as climate change affects the quantity and frequency of rainfall.
Safety and Aesthetics
In addition to preventing damage from fire and wind, parapet walls are often used in place of railings on buildings where maintenance work or other activities will take place on the roof. This is one reason architects and engineers began adopting 36-inch and taller walls in their designs. A higher parapet can help keep occupants safer whether they’re enjoying their building’s rooftop living spaces, or servicing rooftop-mounted HVAC equipment.
To that point, from an aesthetic perspective, parapets are a useful design addition to conceal mechanical equipment from onlookers, or to provide shared spaces with privacy from neighboring buildings.
Are Parapets Part of the Wall or Part of the Roof?
Architects and engineers must be prepared to use best practices for both wall and roof assemblies in parapet construction. From both the exterior and interior sides, parapets must be able to manage water, fire, and wind with the same effectiveness as the building’s roof and walls. In most cases, best practices call for treating the exterior of the parapet as a wall and the interior as a vertical roof.
As a wall extension, the parapet’s exterior face will use the same materials as the rest of the exterior wall, including the sheathing, weather-resistive barrier, and insulation, along with brick or stone veneer, EIFS, metal, or other fascia.
By continuing with these components in a well-designed wall assembly, constructing the exterior-facing side of the parapet is straightforward. However, designers must remember that extending these materials up and overthe parapet may cause problems at the roof-wall connection on the interior (roof) side. Indeed, roof-side parapet construction requires specific considerations and integrations between the roof and the wall.
The interior (roof-side) face of a parapet is where real conversations of roof vs. wall construction take place, and those conversations must include considerations about moisture resistance and fire ratings.
Moisture Management
If a roof assembly calls for a roofing membrane, any parapets must then be considered part of roof (not just another wall) in order to maintain continuity for moisture management. The IBC calls for roofing membranes to wrap at least 8 inches up the parapet from the roof plane to ensure a water-tight seal — a requirement matched by National Roofing Contractors Association (NRCA) recommendations. With that in mind, the interior face of the parapet must be sheathed with a roof board, such as a gypsum cover board, that can accept the roof membrane.
Bond strength and adhesive compatibility between the roof board and roofing membrane is crucial here. Roof designers should identify best-in-class roof boards by looking for UL testing results on these characteristics. High-quality materials will show adequate bond strength to withstand shear and peel forces present on commercial roofs. Additionally, UL testing will confirm that roofing membrane adhesives will be able to weather intense UV exposure, and that the adhesive won’t chemically react and degrade the roof board substrate over time.
In practice, a compatible roof board and roofing membrane must also work in conjunction with flashings used on the parapet. These flashings should cover the top of the parapet and lap over the moisture barrier to direct water away from the roof and walls. A coping cap on top of the assembly provides an additional element of waterproofing protection on all sides of the parapet.
Fire Resistance
As mentioned, extending exterior wall materials up and over the parapet can interfere with construction requirements on the roof side. This is especially true where fire-rated assemblies are called for. Maintaining the continuity of the roof’s fire rating is essential, and using combustible wall-side components, such as OSB or plywood could threaten the roof’s entire fire rating.
For a compliant parapet, non-combustible products must be used on the entire interior surface of the parapet. Materials that meet ASTM E136 are compatible with that requirement, as well as those that meet FM 4470 testing for fire resistance and spread. Gypsum roof board is one material that meets both standards, making it a smart choice to simplify construction by having one product for both the roof cover board and interior parapet substrate.
Wind Uplift
The FM 4470 standard is a comprehensive evaluation of roofing materials that also includes wind uplift considerations. While parapets are used to help flat roofs withstand wind uplift stressors, parapets themselves can become subject to uplift, due to their exposed positions. Roof board used in these designs should meet or exceed FM 4470 to ensure they remain part of the wind uplift solution — and not part of the problem.
Case Study: The Fontainebleau Hotel
The larger the roof, the larger the parapet needed to manage rooftop conditions — and at 600,000 square feet, the Fontainebleau Las Vegas hotel required some very large parapets.
Completed in 2023 after a long and storied construction process, the Fontainebleau stands 735 feet tall (67 stories), making it the tallest occupiable building in Nevada. But at such a height, the hotel’s sprawling roof is susceptible to a variety of challenging conditions, including extremely high winds typical of Las Vegas, intense desert heat, and occasional heavy rainfall.
To manage these conditions, the design team used parapets as tall as 18 and 20 feet around the perimeter of the building, paying close attention to fire resistance and water management. The team paired high-quality gypsum cover board with a 60 mil PVC roofing membrane to create a durable, weather-resistant roof that would protect both the roof surface and everything below it from the potential effects fire and wind uplift, inevitable rain, and puncture damage from traffic or hail.
To ensure long-lasting adhesion of the roof membrane at the roof-parapet connection, the membrane was glued to the gypsum substrate, while the flashing and seams were mechanically attached. This “belts and suspenders” approach is essential in especially high-wind environments. With a code-required 8-inch overlap at the roof-parapet connection, the membrane would be self-supporting. However, the Fontainebleau’s extra-tall parapets called for the membrane to go several feet up the wall, requiring additional attachments to resist direct wind forces, building air pressure, or defects in the wall.
With adjoining and adjacent roof spaces for the Fontainebleau’s hotel, convention center, mechanical areas, and more, the roofing team and general contractors held weekly coordination meetings to manage construction logistics and build a roof assembly that was safe, weathertight, and durable. This collaborative effort, combining high-quality materials and strategic planning, ensured that the Fontainebleau’s roof will withstand the harsh environmental conditions and maintain its structural integrity as the property takes its rightful place as a luxury destination on the Las Vegas Strip.
Smart Parapet Design Stands the Test of Time
Despite their medieval origins, parapet walls remain a vital component of modern architecture. Their historical roots in fortification translate well into building components that defend structures against wind uplift, fire spread, and water management issues.
Still, gone are the days of stone and mortar alone. Today’s parapets must meet stringent building codes and integrate seamlessly with complex roof and wall assemblies. The Fontainebleau Las Vegas exemplifies how modern parapets are employed in large-scale commercial construction and demonstrate the need for durable materials and meticulous design to ensure safety and durability. As both functional and aesthetic elements, parapets continue to evolve, enhancing the structural integrity and visual appeal of contemporary buildings.
About the author: John Chamberlin is the Senior Product Manager at Georgia-Pacific responsible for DensElement Barrier System and the DensDefy line of products. He is actively involved in the building industry, serving as a member of multiple committees and director for the board of the Air Barrier Association of America and a frequent attendee of his local Building Enclosure Council. He graduated from the University of Tennessee with a Bachelor of Science degree in Marketing and later received his M.B.A. from Emory University. For more information, visit buildgp.com.
Parapets for Every Design Style
Just like any other element of a building façade, style can be as important as structure. With this in mind, a variety of parapets exist to help achieve your goals for design and function.
· Plain. A simple vertical extension of the perimeter walls, plain parapets are the most basic and often most cost-effective design style. Plain parapets are ideal for fire prevention, safety, and concealing rooftop mechanicals.
· Paneled. Adding decorative trim or design elements to the exterior side of a wall extension yields a paneled parapet. These are more decorative versions of plain parapets.
· Perforated. If the decorative elements punch through to the interior/roof side of the parapet, you’ve created a perforated parapet. These often come in the form of decorative balustrades and serve a more aesthetic purpose.
· Sloped. On the gable end of a sloped roof, a sloped parapet extends above the roofline but follows the same incline as the roof, providing wind resistance and fire safety while maintaining the architectural style.
· Stepped. Also used primarily on sloped roofs, a stepped parapet increases in height incrementally along the length of the building façade. Stepped parapets can add visual interest, while helping to conceal the roof slope, rooftop mechanicals, and provide wind and fire resistance.
· Coped. The top edge of a parapet usually calls for a sloped cap to manage moisture and protect the parapet assembly. The coping must have enough of a slope and overhang to direct water either down the wall or onto the roof.
· Embattled. The quintessential parapet design, embattled parapets are known for their use atop castles and fortresses but are rarely used today.
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