Understanding Building Construction Types

Importance

The materials and structures involved impact a structure’s fire resistance rating, which pertains to how long the materials used can withstand fire and heat without losing structural integrity. Therefore, understanding and correctly identifying construction types are crucial for building owners and construction workers in determining appropriate safety measures.

For building owners, understanding construction types is crucial for compliance and insurance purposes. It also helps determine the fire safety measures required to protect their property and occupants.

Similarly, construction workers must know how different materials and techniques impact a building’s ability to withstand fire, earthquakes, hurricanes, and other potential hazards. Just as they prepare for accidents on-site, they should also understand how their work ensures the building’s future safety.

The 5 Types of Building Construction

According to the NFPA 220 standard, the type of construction describes a building’s ability to withstand fire. It encompasses all elements, including structural members and non-loadbearing components.

Knowing the five types of construction is essential for meeting safety regulations, especially regarding fire resistance and structural integrity. Here’s a quick overview of each type:

Type I: Fire Resistive

Buildings in this category can endure high temperatures and effectively resist fire. This construction type is typically used in commercial buildings, which often accommodate many people and must comply with strict safety regulations.

Common Building Materials

The most common materials used in Type 1 construction include reinforced concrete, steel, and other non-combustible materials.

Advantages

• Buildings under this category have a high fire resistance rating.
• There’s also a reduced spread of fire and smoke throughout the building.
• It can withstand extreme temperatures for longer, providing more time for evacuation or rescue operations.

Disadvantages

• It’s more expensive due to the use of non-combustible materials and stricter safety standards.

Subcategories

• Type IA: Exterior walls and the structural frame must withstand fire for at least 3 hours.
• Type IB: Exterior walls and the structural frame must withstand fire for at least 2 hours.

Type II: Non-combustible

Non-combustible buildings restrict the spread of fire by using materials resistant to ignition and don’t facilitate the expansion of flames. This type of construction typically appears in industrial and commercial buildings.

Common Building Materials

Non-combustible materials used in Type II construction may include metal framing, concrete blocks, and fire-resistant insulation.

Advantages

• This building construction type has a good fire resistance rating.
• It also has a reduced spread of fire and smoke throughout the building.

Disadvantages

• Similar to Type I, using non-combustible materials makes it more costly than other construction types.

Subcategories

• Type IIA: Exterior walls and structural frames must have 1-hour fire protection.
• Type IIB: Exterior walls, frame, and roof should have minimal fire resistance.

Type III: Ordinary

Type III, or brick-and-joint structures, requires exterior walls and structural elements to be made of non-combustible or limited combustible materials, like concrete or clay tile blocks. Interior structural elements, including walls, columns, beams, floors, and roofs, are either fully or partially made of wood.

Common Building Materials

Type III buildings typically utilize wood or steel for structural elements, with exterior walls made of brick, stone, or stucco.

Advantages

• This type provides better ventilation than Type I and Type II.
• It also effectively prevents fire from spreading from the outside.

Disadvantages

• Interior structural members are susceptible to fire.
• There’s also a potential for fire to spread through hidden spaces.
• The building may be prone to water damage.
• Walls can retain heat.

Subcategories

• Type IIIA: Also called “protected combustible,” the exterior walls offer 2-hour fire protection, while the rest of the building has 1-hour protection
• Type IIIB: Also called “ordinary.” The exterior walls should have 2-hour protection, while the rest have minimal resistance

Type IV: Heavy Timber

Type IV, called mill construction, involves large lumbers connected with metal plates and bolts. This construction method requires structural wood supports like columns, beams, and girders to be at least 8 inches thick, while heavy planks for roofs and floors must be at least 6 inches thick.

Heavy timber construction is common in buildings built before the 1960s. Old churches, factories, and barns usually fall into this category.

Common Building Materials

Heavy timber buildings use large wooden beams and columns, with additional non-combustible materials like steel for reinforcement.

Advantages

• It can withstand fire due to the thick lumber used.
• The natural insulation properties of wood help slow down the spread of fire.
• It’s less likely to collapse due to the heavy mass of the timber.

Disadvantages

• It needs a significant amount of water to extinguish a building due to its combustible materials.
• Fire severity can increase significantly in factories due to the highly flammable products inside.
• It’s prone to the quick spread of flames.

Type V: Wood-Frame

Type V, or Wood Frame construction, features exterior walls, bearing walls, floors, roofs, and supports made mostly or partially of wood or other approved materials smaller than those used in Type IV construction. Wood-framed buildings are among the most common types of residential construction in the US. As the name suggests, this construction type is very flammable.

Common Building Materials

Wood-frame buildings use traditional wood framing techniques and may incorporate other combustible materials like plywood or drywall.

Advantages

• This type of building construction is economical to build.
• It also has a quick construction time.
• It can be easily modified or remodeled.

Disadvantages

• It’s highly susceptible to fire due to its combustible materials.
• Fire can spread quickly, giving occupants minimal time for evacuation or rescue.
• It could completely collapse due to fire or explosion.
• It’s also prone to water damage.

Subcategories

• Type VA: Frame, load-bearing walls, floors, and roofs must use fire-rated materials, a practice common in older construction but rarely seen today
• Type VB: This type doesn’t require a fire-resistance rating for building elements and allows for combustible interior walls and structural components