The 6 Best Fire-Resistant Materials for Building Construction

Nearly 4,000 lives are lost each year to residential fires in the U.S. alone [source: FEMA]. Most of these fatalities happen while people are asleep, as the smoke can cause deep sleep and prevent awareness [source: FEMA]. Ever wonder how your walls might shield you? While no construction material is completely fireproof, well-designed homes and buildings can minimize such tragedies by incorporating materials that offer significant fire resistance.

It's not a matter of if fire will damage a building, but when. Fire-resistant materials simply take longer to be affected by flames. The goal is to design structures that allow enough time for occupants to safely escape, and for emergency responders to intervene. Materials are rated based on how long it takes for fire to compromise their structural integrity. Even heavy timber can be deemed fire-resistant, though it is combustible. On the other hand, metals like aluminum and steel aren’t combustible but can weaken under high heat. Let’s look at some of the best materials for combating destructive fires.

6: Flame-Retardant Natural Products

Natural materials like wood and cotton generally offer limited fire resistance compared to denser materials such as concrete and plaster. Plant-based substances are easily ignited and burn quickly. However, special chemical treatments are available to enhance their fire resistance, allowing them to withstand flames for several minutes [source: Greenfiber]. Treated wood doesn’t catch fire immediately; instead, it forms a charred layer on its surface, which slows further burning. This type of wood is often applied to external structures that are more likely to catch sparks before they reach the interior of a building [source: Forest Products Supply Co.].

Treated cellulose insulation also serves as a flame-resistant alternative to traditional insulators like fiberglass and cotton. The cellulose is primarily made from recycled paper and undergoes a chemical treatment with borate to make it far less flammable than its untreated form. When sprayed into walls, it provides effective heat protection from flames or hot weather conditions [source: Wallender].

5: Fireproof Glass for Windows

While windows are essential for light and visibility, they can pose a fire risk. The intense heat from a nearby blaze can shatter glass even before it directly touches the flames. A broken window then allows the fire to spread easily into the building. Additionally, the heat from an exterior fire might ignite flammable materials inside a structure, even without direct contact.

To safeguard your home, consider installing fire-resistant windows. Dual-paned glass windows, for instance, not only enhance energy efficiency but also double the time it takes for fire to break through them. The outer pane will break first, followed by the inner one. Tempered glass, which is heat-treated to be about four times stronger than regular glass, is another effective option.

While glass blocks don’t offer visibility, they are highly fire-resistant and still allow light to enter. Wired glass, which is tempered glass reinforced with metal wire, is arguably the best option. Doors that need both fire resistance and visibility often feature wired glass windows.

It’s important to consider the framing around your windows as well. Steel framing offers the best fire protection, followed by wood and aluminum. Vinyl is the least effective in fire resistance.

4: Concrete

Concrete, one of the most common building materials, is also an excellent fire-resistant material. It’s noncombustible and has low thermal conductivity, meaning it takes a long time for fire to impact its structural integrity, thus helping prevent the spread of flames. It is notably more fire-resistant than steel and is often used to reinforce steel and protect it from fire.

However, it’s crucial to recognize that not all concrete is the same. Concrete consists of cement and aggregate, and the type and quantity of aggregate can vary. Aggregate typically makes up 60 to 80 percent of the concrete's volume [source: Ashley]. The fire-resistance properties depend on the specific type and amount of aggregate. Natural aggregates usually don’t perform as well. Moisture within the aggregate can expand when exposed to heat, causing the concrete to sinter after prolonged exposure to high temperatures.

Concrete is often regarded as one of the best fire-resistant roofing materials. The roof should not be overlooked in fire protection since it is especially vulnerable to sparks carried by wind from wildfires.

A recent innovation in concrete construction is the Insulating Concrete Form (ICF). This structure is commonly used in the walls of buildings like apartments and commercial spaces. It consists of two polystyrene insulation panels with concrete poured in between, creating a concrete sandwich. ICF is quick and cost-effective to construct, offering a great balance of thermal insulation, soundproofing, and fire resistance [source: PCA].

3: Stucco

Stucco is a type of plaster that has been used for centuries for both artistic and structural purposes. Modern stucco is composed of Portland cement, sand, and lime, and serves as a highly effective, durable fire-resistant finish for buildings. It can cover various structural materials, including brick and wood. Typically, stucco is applied in two or three layers over metal reinforcement mesh. A 1-inch (2.54-centimeter) stucco layer can provide a one-hour fire rating for walls or ceilings, meaning it would take an hour to catch fire [source: Nazarro].

Roof eaves (overhangs) can pose a fire risk, but they can be safeguarded by encasing them with fire-resistant materials. Stucco is often recommended as one of the most effective materials for protecting these vulnerable eaves.

2: Gypsum

Many structural materials require gypsum sheathing to achieve a high fire-resistance rating, and gypsum board is the most widely used fire-resistant interior finish. Known also as drywall, this material consists of a gypsum layer sandwiched between two sheets of paper. Type X gypsum board is specially treated with additives to further enhance its fire-resistant qualities.

The outer paper layer of Type X gypsum board burns slowly and does not contribute to the spread of flames. Additionally, the gypsum board features a noncombustible core that contains water chemically bound in calcium sulfate. When exposed to fire, this water is released as steam, which helps to slow the heat transfer through the gypsum. Even after the water evaporates, the gypsum core continues to resist fire penetration for a while. Builders often apply multiple layers of gypsum board to further enhance its fire-resistance rating.

1: Brick

If we learned anything from the classic children's story of the "Three Little Pigs," it’s that building your house out of brick is wise advice. Not only does brick withstand the big bad wolf's huffing and puffing, but it also stands strong against fires.

Bricks are inherently fire-resistant due to the high heat used in their kiln firing process. However, it's important to note that individual bricks are typically more fire-resistant than a full brick wall. This is because the mortar used to bind the bricks together isn't as fire-resistant. Still, brick is widely regarded as one of the top materials for fire protection. Depending on the wall's construction and thickness, a brick wall can offer anywhere from one to four hours of fire resistance [source: CLM].

While certain materials offer higher fire resistance, other factors like cost, ease of installation, and climate considerations often influence a builder's choice of materials.