Control joints in concrete masonry walls are designed to accommodate movement caused by thermal expansion, moisture changes, and settlement.

Control joints should be placed at locations of stress concentration, such as changes in wall height, changes in wall thickness, or at large wall expanses.

They are not placed at the first course of masonry (which is typically reinforced and anchored to the foundation).

They are generally not placed at window corners or in the center of window openings but rather at planned intervals or changes in geometry.

Placing a control joint at changes in wall height allows movement without cracking.

Cutting holes in beam webs is common for running mechanical, electrical, or plumbing services but must be done carefully to avoid weakening structural integrity.

Holes should be located near mid-span supports (points of low bending moment and high shear) to reduce impact on beam bending strength.

Holes should not be located near areas of maximum bending moment (typically mid-span between supports), because this is where the beam experiences maximum tension or compression.

Locations 2 and 4 are at or near the beam supports (shear zones), and generally small holes can be cut there, following size limits and reinforcement guidelines.

Locations 1, 3, and 5 are closer to mid-span or areas of high bending stress, so holes here risk compromising the beam’s moment capacity.

Purpose of the Air Space in Brick Veneer Walls

In a typical brick veneer cavity wall assembly, there is an air space between the back side of the brick and the sheathing (or water-resistive barrier) of the structural wall. This space is typically 1 to 2 inches wide and serves several critical functions:

Moisture Drainage and Ventilation

Rainwater can penetrate brick veneer through joints and cracks.

The air cavity allows water to drain down the back of the veneer to flashing and out through weep holes.

It also provides ventilation to help dry out the wall assembly.

Minimizing Mortar Bridging

During construction, mortar can drop down into the cavity from bricklaying.

If mortar bridges across to the sheathing, it can create a path for moisture to move into the structure.

The 2-inch cavity helps reduce the chance that mortar droppings will fully bridge the gap, ensuring the drainage plane stays functional.

Why Other Options Are Incorrect:

A. To meet the minimum R-value — The air space in brick veneer is not designed as insulation; its thermal benefit is minimal compared to continuous insulation layers.

B. Allow for differential movement — Brick veneer differential movement is accommodated by wall ties and control joints, not by the air cavity.

C. Provide space for roof drain piping — Roof drainage piping is routed separately and is not part of the brick veneer cavity design.

NCARB ARE 5.0 PDD Study Guide References:

Content Area: Building Envelope Systems — Masonry Wall Assemblies

Source References:

Building Construction Illustrated (Ching) — Brick Veneer Wall Sections and Cavity Function

Architectural Graphic Standards — Masonry Veneer Construction Details

BIA (Brick Industry Association) Technical Notes 21 & 21A — Cavity Wall Design and Construction

Key Principle:

A 2-inch air cavity behind brick veneer is primarily to ensure proper drainage and to minimize mortar bridging, which would otherwise allow moisture intrusion into the building.

A battered (leaning back) face on a dry-stacked retaining wall improves stability against lateral earth pressure by shifting the wall’s resultant closer to/within the middle third of the base, increasing frictional resistance and reducing overturning. It does not significantly change permeability (C) or directly increase cohesion between stones (D), and erosion resistance (B) is secondary compared to stability.

PDD References: Site & foundation systems—retaining wall behavior, active/passive earth pressures; IBC/Geotechnical fundamentals; CSI Div. 32 site improvements.

Given:

The theater doubles its second-floor movie screens, increasing patron traffic.

Existing escalators are two 24-inch wide units, one up and one down, with simultaneous movie start times every 3 hours.

To handle increased traffic:

Increasing existing escalator speed to 130 fpm (option A) is limited by safety and code limits (typically max around 100 fpm); also increases wear.

Installing a new elevator (option B) is helpful for accessibility but does not efficiently handle high flow of large crowds during peak.

Installing a new escalator that reverses direction (option C) (also called a "dance" or "two-way" escalator) allows flexibility to accommodate peak traffic flow—e.g., two escalators up during rush times and one down, or vice versa.

Extending balustrades (option D) improves safety but does not increase capacity.

Therefore, option C is the best solution to manage increased passenger flow.

With outdoor below freezing and indoor RH ~40% continuously, interior vapor will migrate outward. If a proper interior-side vapor barrier/retarder is missing, moisture moves through the wall and can condense and freeze at the cold exterior stone, forming visible ice. Insulation, air spaces, or rain screens help heat/moisture management, but the symptom (ice due to vapor diffusion) points specifically to the lack of an interior vapor barrier in a cold-climate assembly.

PDD references: Moisture control & vapor retarder strategy in cold climates; condensation diagnostics (ASHRAE Fundamentals; ARE 5.0 PDD—Envelope moisture control).

In cold climates, the vapor drive is from the warm interior to the cold exterior during winter. The vapor retarder/barrier belongs on the warm-in-winter side of the assembly—i.e., behind the interior gypsum, before the framing/insulation—to prevent interior moisture from reaching cold layers where it could condense.

PDD references: Psychrometrics & vapor drive; vapor retarder placement (ASHRAE; IBC/IECC guidance; ARE 5.0 PDD—Thermal & Moisture Protection).