Ancient solutions for modern problems: Using clay roof tiles to protect against wildfire

Evidence suggests that natural disasters such as hurricanes, floods, and wildfires are increasing in both frequency and severity,¹ causing significant damage to existing structures and communities.

As architects and builders begin constructing buildings to survive these varied threats, it is important to consider climate resilience as a deciding factor in material selection.

Roofs are the part of homes most vulnerable to ignition during wildfire, and many conventional roofing materials are combustible. In addition to this short-term risk, the materials typically are designed to last only a couple decades, necessitating replacement over time and increasing a structure’s embodied carbon.²

By using clay roof tiles, builders and homeowners can mitigate the risk of destruction from wildfires while also greatly extending a roof’s lifespan—thus minimizing the structure’s contributions to climate change.

Growing wildfire risks for homeowners

Since the 1990s, the number of continental U.S. homes found within the wildland–urban interface (WUI) has more than doubled, meaning that hundreds of thousands of houses are in close proximity to wild vegetation. Wildfires cause most of their insurable damage in these WUI areas because there are more fuels for flames and fewer barriers to limit their spread.

In addition to an expansion in development, the amount of land burning in the United States has been increasing largely due to climate change, with surface area growth of 240% between the 1990s and 2010s.³

Weaknesses of predominant construction

Structures in the WUI are at risk of ignition from two main sources during wildfires: embers and flames. Embers, known in some cases as firebrands, are pieces of burning debris that become airborne during wildfires, often carried for miles before landing. These embers frequently spark secondary fires on structures or vegetation where they land.

Strategic limiting of adjacent vegetation and potential fire sources can protect buildings to some degree from direct contact with flames. However, it is not possible to prevent or limit embers in the same way due to their airborne nature. As a result, embers are responsible for more damage and pose a greater threat to buildings.

Because of their horizontal slopes, roofs are the part of a structure most exposed to embers during a wildfire. Certain roofing materials, such as wood shake shingles, are extremely vulnerable to sparks of this type. These shingles are a threat not only to the buildings they are installed on but also to structures surrounding them. Because they are made of wood, these shingles create more embers as they burn and can lead to further destruction in affected areas.⁴

Benefits of clay tiles in architecture

The use of clay roof tiles in architecture has a long history, tracing back 10,000 years to both China and the Middle East. From these two regions, the common usage of clay roof tiles spread throughout Asia and Europe, and European settlers brought this roofing tradition to the Americas.⁵

Clay roof tiles offer numerous benefits compared to other contemporary roofing materials. For one, clay roof tiles offer significant resistance to damage from wildfires. In the case of Ohio-based manufacturer Ludowici Roof Tile, our tiles experience a peak temperature of 2,100°F (1,149°C) during firing and are incombustible afterward. Due to this high level of fire resistance, clay roof tiles are typically rated as Class A roofing materials by ASTM guidelines. This incombustibility sets clay roof tiles apart from many other roofing materials—while certain types of asphalt shingle and composite roofing materials can achieve similar ASTM ratings, it may be possible for them to burn under specific conditions.

Another advantage of clay roof tiles is their visual adaptability. Through the use of glazes and engobes, the color of tiles can be significantly modified. In some instances, this ability is used to replicate other materials, such as wood shake shingles (Figure 1). In geographic areas where wood shake shingles have an extensive history and significance in regional architecture, clay roof tiles can enable property owners to replicate the appearance of shake without its vulnerability to fire.

The most significant benefit that clay tiles provide for exterior architecture stems from their longevity. While roofing materials such as asphalt shingles, wood shakes, and screw-down metal panels have an expected functional lifespan ranging from 15 to 30 years, we at Ludowici have observed our and other clay tiles remaining intact and fully functional after more than 100 years of use in unforgiving environments. Thus, in addition to reducing costs for building owners, clay roof tiles significantly minimize the embodied carbon of homes and other structures.⁶

Figure 1. Wood shake shingles (left) are shown alongside Ludowici clay tile (right) during a reroofing project. By using engobes and surface effects, the appearance of genuine wood can be replicated without the corresponding fire risk. Credit: Gates Building Envelope

Historical precedent for fire-driven clay tile demand

While current building practices do not prioritize the use of clay roof tiles, the threat of tragic disaster has a history of leading to widespread changes in architectural design. For example, the Great Chicago Fire of 1871 decimated tens of thousands of buildings in that city, and a subsequent fire in 1874 tore through much of what had been rebuilt. City insurers grew fed up with the idea of providing insurance to new buildings designed with the same vulnerabilities as the destroyed structures and began a pressure campaign to institute stricter building standards. Despite initial resistance, they eventually prevailed, and a ban on wooden roofing and flammable structures took effect within Chicago.

This ban led to a surge in demand for fire-proof building materials such as brick, architectural terracotta, and clay roof tiles. The prominent incorporation of these elements into buildings has come to be recognized as a defining aspect of that era’s architecture and has allowed many of these structures to survive to the present day.⁷

Outlook on the clay tile market

As more homes become vulnerable to wildfire, it is important to design new buildings that are resistant to conflagration. The roof is the most vulnerable part of a building during a wildfire, and many roofing options are combustible. Emissions from producing building materials play a large role in driving climate change, and when materials need to be replaced emissions continue to increase.

While not a predominant choice now, the threat of fire has historically led to wider adoption of clay materials in architecture. Traditional ceramic roof tiles offer a fire-resistant and noncombustible roofing option, with a lifespan long enough to minimize embodied carbon and protect homeowners for decades to come.