NCARB PDD Exam With Confidence Using Practice Dumps

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.

IBC governs occupancy classification, occupant loads, and required means of egress. A 300-person taproom triggers egress path requirements under IBC Chapter 10. Objective 1.3 addresses code compliance.

1. Understanding the Diagram

The three sections in the exhibit show different curtain wall mullion profiles (vertical and horizontal sections) designed for glazing systems.

In curtain wall design, aluminum mullions must accommodate:

Structural loads (wind, dead load of glass, seismic)

Thermal expansion and contraction of metal members

Building movement (floor-to-floor deflection, live load, creep, seismic drift)

2. Why Vertical Expansion is Relevant

The vertical mullions in curtain wall systems span multiple floors and are typically anchored at one end and allowed to float/slip at the other end to accommodate vertical building movement.

Movement can be due to:

Thermal expansion of aluminum mullions (aluminum has a high coefficient of thermal expansion).

Inter-story drift from lateral loads.

Floor live-load deflection.

The mullion joinery and connections at the anchors are specifically detailed to allow vertical sliding while maintaining weather seals.

3. Why Other Options Are Incorrect

A. Capillary action — This refers to water movement in small spaces; curtain walls are designed with weeps and pressure-equalized cavities to prevent it, but that is not what the mullion’s slip connections are for.

B. Horizontal expansion — Horizontal movement is generally handled at horizontal mullions/transoms or gasket joints, not the vertical mullion extrusion as shown.

D. Surface tension — Refers to water behavior, not a structural or thermal movement design issue.

4. NCARB ARE 5.0 PDD Study Guide References

Content Area: Building Envelope Systems — Curtain Wall Detailing

Key Sources:

Architectural Graphic Standards — Curtain wall movement joints

Building Construction Illustrated (Ching) — Curtain wall expansion and anchoring details

AAMA (American Architectural Manufacturers Association) Curtain Wall Design Guide — Section on thermal movement and inter-story drift