Chapter 8: Masonry and Ordinary Construction

Comprehensive flashcards covering Chapter 8: Masonry and Ordinary Construction, including material properties, mortars, CMUs, structural behaviors, interior framing, parapets, collapse hazards, tie rods, and fire service concerns.

Why was masonry construction historically designated as "ordinary," and what is ordinary construction classified as in modern building codes?

It was designated "ordinary" because it was commonplace in the 19th and early 20th centuries. Today, ordinary construction is classified in building codes as Type III construction.

What are the primary benefits and drawbacks of masonry construction components?

Primary benefits are durability and resistance to weather, fire, and insects. Drawbacks include deterioration of mortar joints over time, the labor-intensiveness of laying individual units by hand, and a lack of significant tensile strength (they are used to support compressive loads).

What was structural clay tile and why did its use decline?

Introduced in the late 1800s, structural clay tile was a lighter, easier, and faster material used as a structural and fire-proofing element. It remained popular until the 20th century when concrete masonry units (CMUs) took its place.

What are the four primary functions of mortar in masonry construction?

1. Bonds individual masonry components into a solid unit.
2. Cushions rough surfaces to permit uniform transmission of compressive loads.
3. Provides a seal between masonry units.
4. Contributes to the final appearance of the wall.

What are the four main ingredients of modern mortar, and what is its range of compressive strength?

Modern mortar is produced from Portland cement (the bonding agent), hydrated lime, sand, and water. It comes in five basic types with compressive strengths ranging from $75\,\text{psi}$ ($525\,\text{kPa}$) to $2{,}500\,\text{psi}$ ($17\,500\,\text{kPa}$).

Why must older masonry built with sand-lime mortar be repaired with lime mortar rather than modern Portland cement mortar?

Lime mortar (made of lime, sand, and water prior to the 1890s) is significantly softer than modern Portland cement mortar. Using the wrong kind of mortar can reduce the wall's structural stability.

How can the use of master streams during firefighting operations affect mortar joints?

Master streams can weaken mortar either through the physical pressure of the high-velocity stream or via the flushing effect of the water.

What are the five principal types of stone used in stone masonry construction?

Granite, limestone, sandstone, slate, and marble.

How does firing temperature affect the durability of kiln-fired bricks?

The higher the heat used to fire bricks in a kiln, the more durable the ceramic product becomes. In contrast, historical bricks made on-site with low firing temperatures resulted in very soft bricks.

What allowed coal-cinder waste to bond together into early 20th-century cinder blocks, and how are they used today?

Cinders from burning coal contained fly ash, a fine aluminous material that bonds when exposed to water. Today, cinder blocks are the same size as concrete masonry units (CMUs) but are used primarily for non-structural applications.

What are the standard nominal dimensions of a concrete masonry unit (CMU) in the United States?

$8 \times 8 \times 16\,\text{inches}$ ($203 \times 203 \times 406\,\text{mm}$).

What fire resistance rating can exterior bearing walls of fire-rated CMUs or bricks achieve, and how do nonfire-rated hollow concrete blocks perform under fire?

Fire-rated concrete masonry units or bricks can have fire resistance ratings of $2\,\text{hours}$ or more (ICC, 2024). In contrast, nonfire-rated hollow concrete blocks have little fire resistance and may spall and crumble when exposed to fire.

Why can a building with masonry exterior walls not be assumed to be Type III construction simply by viewing its exterior?

Because masonry walls can be combined with diverse interior framing systems. Buildings with masonry exterior walls can be Type I (fire-resistive), Type II (noncombustible/protected noncombustible), or Type III (ordinary), depending on the interior construction.

What is a wythe, and how is horizontal bonding achieved between wythes in a nonreinforced load-bearing wall?

A wythe is a single vertical row or series of rows of masonry units. Horizontal bonding is accomplished by strategically placing bricks (such as header courses) or by using corrosion-resistant metal ties anchored between wythes.

What is the typical maximum height limit for nonreinforced masonry walls, and what historic 1893 building in Chicago exceeded this?

They are usually limited to a maximum height of $6\,\text{stories}$. The Monadnock Building in Chicago, Illinois was built in 1893 to a height of $16\,\text{stories}$ using exterior bearing walls that were $6\,\text{feet}$ ($2\,\text{m}$) thick at the base.

Identify and distinguish the three common brick courses shown in the diagram.

1. Stretcher course: Bricks placed end-to-end.
2. Soldier course: Bricks placed vertically on end (architectural appeal).
3. Header course: Bricks placed with the end facing out (provides horizontal structural bonding between wythes, historically found every 5-8 stretcher courses).

What four factors related to Type III construction and renovations present increased hazards for firefighters?

1. Unprotected voids inside wooden roof and truss channels permit rapid fire spread unless firestopping is applied.
2. Renovations can create large concealed voids above ceilings and below floors.
3. New construction materials used in renovations may reduce load-carrying capacity.
4. Building use may have changed to require higher load capacities than originally designed.

How does steel reinforcement affect the allowable dimensions of load-bearing masonry walls?

Steel reinforcement allows walls to have reduced thickness; for example, reinforced load-bearing masonry walls can be built to a height of $10\,\text{stories}$ or more with a wall thickness of only $12\,\text{inches}$ ($300\,\text{mm}$).

What is Concrete Block Brick Faced (CBBF) construction?

A wall construction system comprising a concrete block wythe combined with an exterior brick wythe, reinforced together by metal tie rods placed between the two wythes.

What interior structural framing components may be found supporting masonry buildings?

Masonry columns or interior load-bearing walls; steel columns, beams, or trusses; and wood beams, columns, and trusses.

What is a beam pocket, and what purpose does a fire cut serve on wood joists resting inside one?

A beam pocket is an indentation several inches deep in a masonry wall that provides a bearing surface for a beam. A fire cut is an angled cut on the beam end that allows it to fall away freely during a collapse without acting as a lever to pry open or push out the masonry wall.

Which three methods are used to support masonry loads over window and door openings?

Lintel (a beam supporting the triangular section of masonry above the opening; most common), Arch (curved member with compressive internal stresses; second most common), and Corbelling (stepped projecting ledges).

Why are wood lintels rarely used in modern masonry construction?

Wood lintels shrink over time and are susceptible to wood decay caused by moisture absorption from direct contact with masonry.

What is a parapet and what fire-protection role does it play?

A parapet is an extension of an exterior fire wall above the roofline. It prevents the radiant heat of flames from igniting adjacent combustible roof assemblies or closely spaced adjoining structures.

What are artificial parapets constructed from, and what operational forces can cause parapets to fail?

Artificial parapets are made from Exterior Insulation Finishing System (EIFS) materials and provide zero fire resistance. Parapets can lose structural integrity from high winds (especially with deteriorated mortar), roof collapses, forceful impacts from aerial ladders, or the direct force of master streams.

What hazard is introduced by decorative false fronts, such as a mansard-style fascia?

They form cornices extending beyond the exterior wall, creating concealed combustible void spaces through which fire can spread outside the protection of the masonry wall.

According to collapse zone safety standards, what is the minimum required distance for a collapse control zone, and where is apparatus safely positioned?

The collapse zone must extend at least $1.5 \times$ the height of the building around its entire perimeter (e.g., a $20\,\text{ft}$ / $6\,\text{m}$ high building requires a $30\,\text{ft}$ / $9\,\text{m}$ collapse zone). Apparatus should be staged in line with the angle formed by the building's corners.

Why are corners, stairwells, and elevator shafts the structurally strongest points in a masonry building?

Intersecting masonry walls provide mutual lateral support and reinforce each other; points of intersection resist the horizontal forces that cause unbraced walls to collapse outward.

What technique and shape should firefighters use when breaching a masonry wall?

Firefighters locate a weak point in the mortar or concrete and work progressively downward in a corbelling shape until the opening is sufficiently large, while watching for utilities and load-bearing disruption.

What three steps are used to stabilize an exterior masonry wall that is bulging or leaning using tie rods?

1. Steel tie rods are extended inside the building through the masonry walls parallel to the floor joists.
2. The rods are secured to the exterior wall face with bearing plates or structural washers.
3. Tie rod tension is adjusted using an interior turnbuckle.

How can firefighters distinguish tie rods added as post-construction wall repairs from original construction tie rods?

Bearing plates installed for repairs are typically: less compatible with the building's architecture, not uniformly aligned on the wall, accompanied by localized mortar repairs around the plate, or made from atypical structural shapes such as steel channels instead of washers.

What hazard do steel tie rods create under fire conditions?

Fire heats and elongates (stretches) the steel tie rods, eliminating their holding tension and weakening the supported masonry walls.

What are primary visual warning signs of imminent structural collapse in a masonry wall?

Shifts or changes in the alignment of existing cracks, rapid growth of cracks during operations, and light from the fire visibly shining through the wall.

What is spalling in masonry construction?

The violent expansion of trapped moisture within masonry units caused by fire heat. The resulting internal tensile forces cause the surface to fracture, producing violent chipping, pitting, and disintegration.

Distinguish between compressive strength, bonding strength, and flexural strength in masonry.

• Compressive strength: Ability to resist a crushing load applied to top and bottom without fracturing or deforming. • Bonding strength: Measurement of adhesion between similar or dissimilar materials (e.g., mortar to CMU, concrete to rebar). • Flexural strength: Ability of a material to bend under a three-point load without major deformation or breaking.