Construction Terms Glossary
Plain-language definitions for common construction and building terms. Each definition links to the relevant calculator where applicable.
A
AWG (American Wire Gauge)
The standard sizing system for electrical wire in the US. Counterintuitively, lower AWG numbers mean thicker wire: 12 AWG wire carries more current than 14 AWG. Common residential gauges are 14 AWG (15A circuits), 12 AWG (20A), and 10 AWG (30A).
Wire Gauge Calculator →B
Board Foot
A unit of lumber volume equal to 1 foot × 1 foot × 1 inch (144 cubic inches). Used to price and purchase rough hardwood lumber. A 2×6 stud that is 8 feet long equals 8 board feet: (2 × 6 × 96) / 144.
Board Feet Calculator →BTU (British Thermal Unit)
The amount of heat needed to raise one pound of water by 1°F. HVAC equipment is rated in BTU/hour. A room needing 12,000 BTU/hour of cooling requires a 1-ton air conditioner (12,000 BTU = 1 ton).
BTU / AC Size Calculator →C
Cubic Yard
The standard unit for ordering bulk concrete, soil, gravel, and mulch. One cubic yard equals 27 cubic feet (3 ft × 3 ft × 3 ft). A 10×10 ft slab at 4 inches thick requires approximately 1.23 cubic yards of concrete.
Concrete Slab Calculator →Concrete Footing
A widened concrete base placed below frost depth that distributes the load of a foundation wall, column, or post to the soil. Footings must extend below the local frost line (18–48 inches depending on climate) to prevent heaving.
Footing Calculator →Cubic Foot
A volume unit equal to a 1-foot cube (12 in × 12 in × 12 in). Mulch, soil, and gravel are often sold in cubic foot bags (1, 1.5, or 2 cu ft per bag). One cubic yard = 27 cubic feet.
Mulch Calculator →J
Joists
Horizontal structural members that span between beams or walls to support a floor or ceiling. Floor joists are typically 2×8, 2×10, or 2×12 dimensional lumber spaced 12, 16, or 24 inches OC. Span tables from the AWC specify the maximum allowable joist span.
L
Load-Bearing Wall
A wall that carries structural loads from above (floors, roof, upper walls) down to the foundation. Removing a load-bearing wall without proper header installation can cause structural failure. Non-load-bearing (partition) walls carry only their own weight.
M
Mortar Joint
The layer of mortar between masonry units (bricks, blocks, or pavers). Standard mortar joint width is 3/8 inch for brick and block construction. Joint width affects the total number of masonry units needed and mortar quantity.
Brick Calculator →O
On Center (OC)
The distance between the centers of two adjacent structural members — studs, joists, or rafters. Standard wall framing is 16 inches OC; some exterior walls and floor systems use 12 or 24 inches OC. OC spacing determines stud count for a given wall length.
Wall Framing Calculator →P
Plumb and Level
Plumb means perfectly vertical (aligned with gravity); level means perfectly horizontal. Posts, walls, and door frames must be plumb. Floors, windowsills, and countertops must be level. Out-of-plumb framing causes doors and windows to bind over time.
R
Roofing Square
A unit of roofing area equal to 100 square feet. Roofing materials (shingles, underlayment, metal panels) are sold and estimated in squares. A 2,000 sq ft roof area equals 20 squares. Add 10–15% for waste and hip/valley cuts.
Roofing Shingles Calculator →R-Value
A measure of thermal resistance — how well an insulation material slows heat flow. Higher R-value = better insulation. The DOE recommends R-38 to R-60 for attics in most US climate zones. R-value depends on insulation type, thickness, and density.
R-Value Calculator →Rise and Run (Stairs)
The vertical distance each step climbs (rise) and the horizontal depth of each tread (run). Building codes typically require a maximum rise of 7¾ inches and minimum run of 10 inches. The formula: (2 × rise) + run = 24–25 inches.
Stair Stringer Calculator →Roof Pitch
The slope of a roof expressed as a ratio of rise to run (e.g., 4:12 means 4 inches of rise per 12 inches of horizontal run). Pitch affects the roof area multiplier, shingle quantity, and minimum recommended material type. Roofs below 2:12 pitch require different waterproofing than steeper slopes.
Roof Pitch Calculator →S
Stringer (Stairs)
The diagonal structural member on each side of a staircase that supports the treads and risers. Most residential stairs use two or three stringers. The stringer is notched for each step based on the rise and run dimensions.
Stair Stringer Calculator →Sheathing
Structural panels (OSB or plywood) fastened to wall studs, roof rafters, or floor joists to add rigidity to the frame and provide a nailing surface for cladding. Wall sheathing thickness is typically 7/16 or 1/2 inch for standard framing.
T
Thinset
A cement-based adhesive mortar used to bond tile to a substrate. Standard thinset covers approximately 40–50 sq ft per 50lb bag at 3/16-inch coverage. Use medium-bed thinset for large-format tile (over 15 inches) to achieve full back coverage.
Tile Calculator →V
Voltage Drop
The reduction in electrical voltage as current flows through wire resistance. The NEC recommends keeping voltage drop to 3% or less on branch circuits. Long wire runs or heavy loads require upsizing to a larger AWG gauge to maintain adequate voltage at the load.
Wire Gauge Calculator →W
Waste Factor
A percentage added to material calculations to account for cuts, defects, breakage, and leftovers. Standard waste factors: flooring 10%, tile 10–15% (15% for diagonal patterns), roofing 10–15%, lumber 5–10%. Our calculators apply waste automatically.