Project Planning & Design Key Terms
Master these terms for the PPD division.
Structural Systems
Moment Frame
A structural system that resists lateral loads through rigid beam-column connections. Provides open floor plans but is more expensive than braced frames. Available in steel and concrete.
Braced Frame
A structural system using diagonal members to resist lateral loads. More economical than moment frames but restricts wall openings where bracing occurs.
Shear Wall
A vertical structural element that resists lateral forces (wind and seismic) in its own plane. Constructed of concrete, masonry, or wood sheathing. Very stiff and efficient but must be planned early.
Diaphragm
A horizontal structural element (typically a floor or roof deck) that transfers lateral loads to vertical resisting elements (shear walls or frames). Functions like a deep beam laid flat.
Load Path
The continuous route through which gravity and lateral forces travel from the point of application to the foundation. Every structural element must connect to the next - any break in the load path can cause failure.
Building Envelope
Vapor Barrier (Vapor Retarder)
A material that restricts the passage of water vapor through a wall assembly. Placed on the warm side of the insulation - interior side in cold climates, exterior side in hot-humid climates. See our building envelope guide for more on moisture control.
Air Barrier
A continuous material or assembly that prevents uncontrolled air leakage through the building envelope. Must be continuous, durable, and properly sealed at all joints and penetrations. Not the same as a vapor barrier.
Thermal Bridge
A building element that conducts heat significantly faster than surrounding materials, creating a "bridge" for heat transfer. Common at steel studs, concrete balconies, and window frames.
R-Value
A measure of thermal resistance. Higher R-value = better insulation. R-values of individual layers can be added together for the total assembly R-value.
U-Factor
A measure of heat transfer rate through an assembly. U = 1/R (for the total assembly). Lower U-factor = better insulation. Used in energy code compliance.
Drainage Plane
A water-resistant surface behind the exterior cladding that directs water downward and out of the wall assembly. Works with flashing and weep holes to manage water that penetrates the cladding.
Fire Protection
Fire Wall
A fire-rated wall (2-4 hour rating) that extends from the foundation to or through the roof, creating separate buildings for code purposes. Must be structurally independent so collapse on one side does not affect the other. Learn more about fire protection systems.
Fire Barrier
A fire-rated assembly (1-2 hour rating) that separates different occupancies or creates fire areas within a building. Does not need to be structurally independent.
Fire Partition
A 1-hour rated wall used to separate dwelling units, guest rooms, and corridor walls in certain occupancies.
Smoke Barrier
A continuous membrane (1-hour rated) designed to restrict smoke movement. Required in certain institutional and healthcare occupancies.
HVAC Systems
Variable Air Volume (VAV)
An HVAC system that varies the amount of conditioned air supplied to each zone while maintaining a constant supply temperature. Provides good zone control and energy efficiency for large buildings.
Constant Air Volume (CAV)
An HVAC system that delivers a constant airflow rate and varies the supply air temperature. Simpler but less energy-efficient than VAV.
Dedicated Outdoor Air System (DOAS)
A system that handles ventilation (outdoor air) separately from space conditioning. Often paired with radiant systems or fan coils for improved efficiency and indoor air quality.
Accessibility
Accessible Route
A continuous, unobstructed path of travel that complies with ADA requirements. Minimum 36 inches wide (44 inches preferred). Must connect all accessible building elements.
Clear Floor Space
The minimum unobstructed floor area required for wheelchair access. Typically 30 inches by 48 inches for a forward or parallel approach.
See the structural systems cheat sheet, fire protection cheat sheet, and ADA cheat sheet for quick reference tables.
Related Resources
- PPD Study Guide - comprehensive overview of Project Planning & Design
- Structural Systems Deep Dive
- Building Envelope Deep Dive
- Fire Protection Deep Dive
- HVAC Systems Deep Dive
- ADA Accessibility Deep Dive
- Egress Requirements Deep Dive
- Load Path Deep Dive
- Building Envelope Cheat Sheet
- PPD Exam Tips
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