Structural Forces, Building Materials, and Construction Types for Firefighter Safety

Which of the following BEST describes a compressive force?

A force that pushes a material together; for example, the walls in a house are in compression.

Tensile force is BEST described as which of the following?

A force that pulls materials apart.

A cardboard tube standing on its end is an example of which type of force?

Compressive.

Which of the following BEST describes a torsional load?

A load that creates rotating forces in a structural element.

A dead load is BEST described as which of the following?

The weight of the building itself — the permanent loads of all the materials that make up the building.

A live load is BEST described as which of the following?

A load that is imposed by the use of the building including people, furniture, snow, and water.

An impact load is BEST described as which of the following?

A load imposed suddenly; the classic example is a firefighter's pack load.

A concentrated load is BEST described as which of the following?

A load on a specific area of a building, such as a large safe brought into the middle of a building, magnified greatly compared to stepping slowly onto a ladder.

Axial loads go directly through the center of a structural element such as a column. What does this type of load result in?

The element being placed in either pure compression or pure tension.

Why are occupancy classifications important to firefighters?

They can be used to predict characteristics, including the types of hazards and situations that might be encountered in the building.

According to the text, what is the fire load of a building?

The amount of combustible material in the building and how much heat those materials can generate.

What is the most commonly used building material in the United States?

Wood.

Approximately what percentage of civilian single-family homes are made predominantly of wood?

90%.

As a general rule, wood beams are used at 10 ft (3 meters) in length at a temperature of what?

1000°F.

Which of the following BEST describes solid lumber?

Traditional wood that was built with wood dimensions; it is cut down to nominal sizes and the actual dimensions are smaller than the nominal size.

Engineered wood (also called composite wood) is manufactured from wood and:

Glue or adhesive.

Which of the following BEST describes mass lumber products?

Large-scale engineered materials designed to replace structural materials such as concrete and steel; these materials allow lightweight structures to be built from wood.

Which of the following is NOT one of the four types of mass lumber products?

Cross-laminated timber (CLT).

What is a safety concern specific to fire-retardant treated (FRT) wood, particularly wood used in the 1980s?

FRT wood was found to be structurally deficient under normal heat conditions, particularly in the 1980s; there were thousands of reports of roofs failing within 1 to 3 years of installation.

Masonry is blocks of stone, concrete, or brick stacked on top of one another. The individual blocks are bonded together using:

Mortar, which is produced by mixing sand, lime, water, and cement.

Concrete masonry units (CMUs) are also known as:

Concrete-masonry units; they are similar to concrete and can be placed over a wood-frame building to make it appear more substantial.

What is mortar made of?

Mortar is produced by mixing sand, lime, water, and cement.

What are concrete masonry units (CMUs) also known as?

Concrete masonry units; they are similar to concrete and can be placed over a wood-frame building to make it appear more substantial.

How can a masonry wall act as a fire wall?

It extends from below grade through the roof of the building and is still standing; as long as the masonry wall remains upright, it will prevent the fire from spreading to the other side.

What is a major hazard of masonry walls during a fire?

Masonry walls can collapse if the masonry mortar and the wall have been compromised; if damaged by fire for a prolonged time, they can be a deadly hazard to firefighters.

In what condition is concrete strong?

Concrete is strong in compression but very weak in tension.

What is spalling in concrete?

Spalling is the process where water trapped inside concrete turns to steam when exposed to fire, creating internal pressure that causes the concrete to break apart.

What does reinforced concrete address?

Reinforced concrete uses steel reinforcing bars (rebar) to address concrete's weakness in tension.

At what temperature does steel begin to lose strength?

Steel begins to lose strength at temperatures as low as 400°F (204°C).

At what temperature does steel reach critical temperature?

Steel reaches critical temperature at 1000°F (538°C).

What does intumescent coating do when exposed to fire?

It puffs up to create a layer that insulates and protects the steel from the fire.

What is a key difference between aluminum and steel when exposed to fire?

Aluminum expands more extensively than steel when heated and loses its strength quickly when exposed to fire; it melts and drips in a fire.

What is one notable application of aluminum as a structural material?

Light-duty applications such as awnings, sliding, and window frames, door frames, roof panels, and sunshades.

What are the standard sizes for gypsum board?

Gypsum board is manufactured in sizes of 4 ft by 8 ft (1.2 m by 2.4 m) or larger.

Why does gypsum board provide fire resistance?

When heated, gypsum board is inherently fire-resistant; gypsum does not burn, and it protects the wood from fire until the calcium compound deteriorates.

What is lath and plaster?

Lath and plaster is a type of wall made by combining gypsum, lime, or cement water, and sand, applied to wood lath strips.

What are other membrane materials made from mineral fibers commonly used for?

Suspended ceilings.

What type of glass is treated to be much stronger than ordinary glass?

Tempered glass.

What is wired glass?

Wired glass is made by molding tempered glass with a reinforcing wire mesh inside it.

What type of glass usually deforms instead of breaking?

Laminated glass.

What is a limitation of glass blocks?

They have limited ability to transmit light through the wall.

What best describes thermoplastic material?

A plastic material that can be melted and reformed; when exposed to heat it will eventually melt.

What best describes thermoset material?

A plastic material that is formed into a shape by cooling and hardening; it does not melt when exposed to heat but will eventually combust.

What should be evaluated with caution in modern furnished structures suspected to have small fires?

Plastics produce toxic gases as well as very dense, dark smoke.

What is a material that never burns?

A material that is always noncombustible.

At what temperature can plastics ignite?

500°F (260°C).

What is a fire resistance rating?

A rating of a material or component based on the length of time that the material or component is resistant to fire while maintaining its integrity.

What is the primary purpose of a building's foundation?

To transfer the weight of the building and its contents to the ground.

What materials are modern foundations usually constructed of?

Concrete or masonry.

What is the primary function of ceilings in a building?

To hide the structural components of a building; ceilings conceal heating, ventilation, and air-conditioning systems.

What additional concern exists for firefighters regarding ceilings?

Ceilings can be part of a fire-resistive assembly; fire can easily spread through the ceiling void horizontally.

What materials can components of a fire-resistive floor be constructed of?

Concrete, masonry or gypsum board; if steel beams are used, they must be supported by a system of trusses.

How long can a decking in an unprotected wood-supported floor typically contain a fire?

1 hour or more.

How long did an unprotected lightweight engineered I-joist fail in a residential floor assembly according to a NIOSH study?

19 minutes.

What type of construction provides a resistant wood floor?

I-beam construction which is often found in old mill buildings.

What does a load-bearing wall provide?

Structural support by supporting a portion of the building's dead load.

What does a non-load-bearing wall do?

Supports only its own weight; it can be removed without compromising the structural integrity.

What describes a curtain wall?

They are non-load-bearing and are typically not load-bearing walls.

What is the primary concern with parapet walls during a fire?

Parapets can collapse onto the street, onto firefighters, or onto roof sections; this is a major safety concern.

What is the primary purpose of a roof?

To protect the inside of the building from the weather; in some cases, the roof also is vital to the stability of the building.

What materials does roof decking consist of?

Solid wood joists, beams, and rafters; solid wood joist mounted in an inclined position to support the roof.

How is a pitched roof described?

A roof that has slopes or inclined surfaces.

What layers are included in the decking of flat roofs?

Fill, tar paper, roofing felt, tar or asphalt, and sometimes foam plastic insulation.

What happens if the roof does not have the proper slope?

It can cause a collapse.

What are wood shingles also called?

Cedar shakes.

What is a key concern with fiberglass decks?

The material sits directly related to the cost of materials and the type of roof covering; it will not support your weight.

How long does it typically take an ordinary wood door to provide some barrier during a fire?

Several additional minutes.

Which type of door provides greater security?

Hollow-core wooden doors.

For how many minutes are most metal doors manufactured for fire resistance?

20 minutes.

What is the primary purpose of fire doors and fire windows?

To prevent the passage of flames and heat.

What is the most flammable exterior siding option?

Wood shakes and shingles.

What is the advantage of brick veneer as exterior siding?

It provides a durable and aesthetically pleasant surface; it is not structural.

What does the term interior finish refer to?

The exposed interior surfaces of a building.

What do interior finishes affect?

How quickly a flame will ignite the materials; how quickly a flame will spread across the surface of the materials; how much energy the materials will produce; and how much smoke the materials will produce.

Where are Type I construction buildings commonly found?

In high-rise buildings, hospitals, and schools.

What is required in terms of sprinkler systems in a Type I building?

If the building exceeds specific height and area limitations, codes generally require the use of fire-resistive walls and floors to subdivide the building.

What types of buildings most commonly use Type II construction?

Commercial buildings, warehouses, shopping centers, or 'big box' stores.

What is the fire-resistance rating for load-bearing walls of an unprotected Type II building?

0 hours — no fire-resistance rating required.

What is Type III construction used for?

Buildings of up to four stories but can sometimes be found in buildings as tall as eight or more stories.

What materials can the interior structural components of Type III construction be made of?

Wood or other combustible materials.

What is the minimum size of wood posts used in Type IV construction supporting floor loads?

6 x 8 inches for posts supporting floor loads.

What are the minimum size beams in Type IV construction?

6 to 8 inches wide with a top deck of wood serving 2 to 3 inches.

What is a key fire concern of Type V buildings?

They are very resistant to fire due to their solid construction.

What can easily damage or destroy wood-frame buildings?

Fire

What type of construction is referred to as Type V in the United States?

Wood-frame construction

What is Type IV (heavy timber) construction also known as?

Mill construction

Why is balloon-frame construction a major fire hazard?

It creates an open channel from the basement to the attic that fire and gases can travel through, allowing fire to spread rapidly.

What must firefighters do when attacking a balloon-frame or platform-frame building?

Check for hidden fires and void spaces; they should open the void spaces or check for hidden fires to prevent rapid vertical extension.

What safety tip is important regarding balloon-frame and platform-frame construction?

Many buildings have a masonry veneer on the exterior walls, which may give the impression that the walls are solid brick or masonry; unfortunately, brick veneer does not reduce the risk of fire spread.

What is a hybrid building?

A building constructed with one part using one type of construction and another part from a different type.

What are key characteristics of a Cape Cod home?

High-pitched roof and a half story on the second floor; typically smaller footprint than colonial structures; feature a door centered at the front flanked by windows.

What does the first floor of a colonial home usually contain?

The living room, dining room, and kitchen area.

What layout do typical ranch houses have?

Open layout for the living, dining, and kitchen areas; they often have long, low-pitched roofs and large picture windows along the front.

What is the entry layout of a split-foyer home?

There is a landing and a set of stairs going up to the main level or down to a lower level.

What is a key tactical concern for firefighters in split-level homes?

The split-level design is confusing, making it critical to understand the point from the front.

What is a key concern for firefighters in contemporary/modern homes?

Modern homes typically have an inability to predict what typical layouts may be.

What is crucial for firefighters to understand before entering a building?

Conducting a size-up and understanding the structural issues prior to entering.

What is an indicator of potential collapse?

Cracks in walls, especially cracks that develop or grow during the fire

What is a lean-to floor collapse?

A partial collapse where one side of the floor has collapsed and the other side is still attached

What occurs in a V-shaped collapse?

The center section of a floor falls while the two ends remain attached, forming a V-shape when looking at it from the side