Structural Engineering Glossary
Plain-language definitions of the terms your structural engineer, contractor, or home inspector might use. Bookmark this page for quick reference.
B
Beam
A horizontal structural member that supports loads from above and transfers them to columns, posts, or walls at each end. Common types in residential construction include engineered lumber (LVL), steel I-beams, and dimensional lumber built-up beams.
Bearing Wall
A wall that supports structural loads from the roof, floors, or walls above it, transferring those loads down to the foundation. Removing a bearing wall without installing a properly engineered beam can cause structural failure. Also called a load-bearing wall.
Bowing Wall
A foundation or basement wall that curves inward due to lateral soil pressure. Bowing walls indicate that the wall is being pushed beyond its structural capacity and typically require engineering evaluation and reinforcement.
C
Carbon Fiber Reinforcement
A repair method where high-strength carbon fiber strips are bonded to bowing or cracked foundation walls to resist further movement. Carbon fiber repairs are non-invasive, don't reduce interior space, and provide significant tensile strength.
Crawl Space
The area beneath a home between the ground and the first floor, typically 18 inches to 4 feet tall. Crawl spaces provide access to plumbing, electrical, and structural components but are vulnerable to moisture problems in North Carolina's humid climate.
D
Dead Load
The permanent weight of a structure itself, including walls, floors, roof, and all fixed components. Dead loads are constant and predictable, unlike live loads which change over time.
Differential Settlement
Uneven settling of a foundation where one area sinks more than another. Differential settlement causes cracks, sloping floors, and misaligned doors. It is the most common type of foundation problem in the Triangle region due to expansive clay soils.
E
Engineered Lumber
Manufactured wood products designed to be stronger and more consistent than traditional dimensional lumber. Common types include LVL (Laminated Veneer Lumber), PSL (Parallel Strand Lumber), and I-joists. Frequently used for beams and headers in residential construction.
Expansive Soil
Soil that swells significantly when wet and shrinks when dry. The clay soils found throughout the NC Triangle region are highly expansive, making them the primary cause of residential foundation problems in the area.
F
Floor Joist
Horizontal framing members that support the floor and span between beams, foundation walls, or other supports. Common sizes in residential construction are 2x8, 2x10, and 2x12, spaced 16 or 24 inches apart.
Footing
The wide, flat concrete base of a foundation that distributes the building's weight over a larger area of soil. Footings are typically wider than the walls or columns they support. Undersized or improperly placed footings can contribute to foundation settling.
Foundation
The structural system that transfers the weight of a building to the ground. Common residential foundation types include crawl space (perimeter walls with interior piers), slab-on-grade (concrete poured directly on soil), and full basements. The foundation is arguably the most critical structural component of any building.
G
Girder
A large beam, typically the main horizontal support running the length of a crawl space or basement. Girders carry floor joists and transfer their loads to support piers or columns. Sometimes used interchangeably with 'beam' in residential construction.
H
Header
A horizontal beam placed above a door, window, or other opening in a load-bearing wall. The header carries the weight that would otherwise be supported by the wall framing where the opening was created. Proper header sizing is critical for structural integrity.
Helical Pier
A steel foundation support that is screwed into the ground until it reaches stable soil or bedrock. Helical piers are used to stabilize and sometimes lift settling foundations. They are one of the most reliable repair methods for homes on expansive clay soils.
L
Lateral Pressure
Horizontal force exerted on foundation walls by the surrounding soil. When soil becomes saturated with water or expands due to clay content, lateral pressure increases and can cause walls to bow, crack, or shift inward.
Live Load
Variable weight that a structure must support, including people, furniture, appliances, and stored items. Building codes specify minimum live load requirements for different types of spaces (bedrooms, living areas, decks, etc.).
Load Path
The continuous chain of structural components that transfers loads from the roof down through the walls, floors, and foundation to the ground. Every structural element must be properly connected to create a complete load path. Breaks in the load path cause structural problems.
P
PE Stamp
The official seal of a licensed Professional Engineer applied to documents. A PE stamp signifies that the engineer has reviewed, analyzed, and taken legal responsibility for the technical content. PE-stamped documents are required by building departments for structural permits and are accepted by insurance companies as authoritative documentation.
Pier
A vertical support column in a crawl space or basement that transfers loads from beams to footings in the ground. Piers can be made of concrete block, poured concrete, brick, steel, or wood. Deteriorated or inadequate piers are a common cause of sagging floors.
Professional Engineer (PE)
An engineer who has met education, experience, and examination requirements and is licensed by the state to practice engineering. In North Carolina, only a licensed PE can stamp structural documents for permitting and legal purposes. PEs carry professional liability for their work.
Push Pier
A steel pier driven vertically into the ground using the weight of the building as resistance. Push piers reach load-bearing soil or bedrock to stabilize settling foundations. Similar in function to helical piers but installed differently.
R
Rafter
A sloped structural member that supports the roof, running from the ridge (peak) to the eave (edge). Rafters are individual pieces cut and installed on-site, as opposed to trusses which are pre-manufactured. Rafter size and spacing determine the roof's load capacity.
Retaining Wall
A wall built to hold back soil on a slope or grade change. Retaining walls must resist lateral soil pressure and may require engineering design, especially when over 4 feet tall. Failing retaining walls can impact adjacent structures and property.
S
Shear Wall
A wall designed to resist lateral forces such as wind or seismic loads. Shear walls prevent a building from racking (leaning sideways) by transferring horizontal forces to the foundation. Proper shear wall placement and bracing is critical for structural stability.
Sill Plate
The horizontal wood member that sits on top of the foundation wall and serves as the transition between the masonry foundation and the wood framing above. Sill plates are anchored to the foundation and are a common location for moisture damage and wood rot in NC homes.
Sistering
A repair technique where a new structural member is attached alongside a damaged or undersized existing member to reinforce it. Commonly used to strengthen weakened floor joists or rafters without removing the original framing.
Slab-on-Grade
A type of foundation where a concrete slab is poured directly on the ground surface. The slab serves as both the foundation and the floor. Common in newer construction and ranch-style homes in the Triangle. Slab foundations are harder to inspect because structural components are hidden.
Span
The distance a structural member (beam, joist, rafter) covers between its supports. Longer spans require larger or stronger members. Maximum allowable spans for different sizes and species of lumber are specified in building codes and span tables.
Stair-Step Crack
A crack pattern in brick or block walls that follows the mortar joints in a diagonal, staircase-like pattern. Stair-step cracks are one of the most recognizable signs of foundation settlement and indicate that different parts of the wall are moving in different directions.
Structural Inspection
A focused evaluation of a building's structural components by a qualified professional, typically a licensed PE. Unlike a general home inspection, a structural inspection provides engineering analysis and a PE-stamped report. Common reasons include foundation concerns, real estate transactions, and renovation planning.
Subfloor
The structural layer of flooring installed on top of floor joists, beneath the finished floor. Typically plywood or oriented strand board (OSB). The subfloor provides a flat surface for finished flooring and distributes loads to the joists below.
T
Truss
A pre-engineered, factory-built roof framing assembly made of triangulated wood members connected by metal plates. Trusses are designed to span large distances without interior support. Individual truss members should never be cut or modified without engineering approval.
V
Vapor Barrier
A moisture-resistant material (typically heavy polyethylene sheeting) installed on the ground in crawl spaces to reduce moisture migration from the soil into the crawl space. A properly installed vapor barrier is one of the most important moisture control measures for crawl space foundations in NC.
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