Construction Glossary

Plain-language definitions for common construction terms. Each entry links to the relevant calculator where applicable.

A B C D F G H J K L M N O P R S T U V W

A

Aggregate→ Concrete Calculator: The sand, gravel, or crushed stone mixed with cement and water to make concrete. Fine aggregate (sand) fills the gaps between coarse aggregate (gravel or crushed stone), and together they make up the bulk of the mix. The type and size of aggregate affects both the strength and workability of the finished concrete.
Anchor bolt→ Concrete Calculator: A threaded steel bolt embedded in concrete to secure structural members above it, such as a sill plate or steel column base. The bolt is set before the concrete cures, leaving the threaded end exposed so a nut and washer can fasten the wood or metal to the slab. Placement and spacing are typically specified by local building codes.
Attic ventilation: The system of intake and exhaust vents that moves air through an attic space to prevent heat and moisture buildup. Adequate ventilation helps extend the life of roofing materials and reduces energy costs by preventing heat from radiating into living spaces. A common standard is one square foot of net free vent area per 150 square feet of attic floor.

B

Bearing wall: A wall that carries structural loads from the floor or roof above down to the foundation, as opposed to a partition wall that only divides space. Removing or modifying a bearing wall requires adding a properly sized beam and posts to carry the load. Identifying bearing walls incorrectly is one of the most common and costly renovation mistakes.
Blocking→ Deck Calculator: Short pieces of lumber installed between studs or joists to add rigidity, prevent twisting, or provide a nailing surface for finish materials. Blocking between floor joists transfers lateral loads and keeps joists from rolling or rotating under load. It is also installed in walls to back cabinets, grab bars, and heavy fixtures.
Board foot→ Board Feet Calculator: A unit of lumber volume equal to a piece that is 1 inch thick, 12 inches wide, and 12 inches long — or any combination that equals the same volume. A 2×6 board that is 8 feet long contains 8 board feet. Hardwood and specialty lumber are typically priced per board foot rather than by lineal foot.

C

Cantilever→ Deck Calculator: A structural element that extends beyond its support point without a post or support at the free end, relying on the strength of the connection at the supported end to resist bending. Deck boards often cantilever past the last joist by a few inches. Building codes limit how far joists and beams can cantilever based on the lumber species, size, and load.
Caulk: A flexible sealant applied to gaps, cracks, and joints between materials to prevent air, water, or pests from passing through. Different formulations are used for different applications — silicone caulk for wet areas like tubs and sinks, paintable acrylic latex for interior trim, and polyurethane for outdoor use. Caulk is not a structural adhesive and will not hold materials together under load.
Cripple stud: A short stud that fills the space above a door or window header, or below a window rough sill, to maintain the regular stud spacing pattern and provide nailing for sheathing and drywall. Cripples do not carry vertical load from above the opening — that load is transferred through the header to the king and jack studs on each side.
Cubic yard→ Concrete Calculator: A unit of volume equal to 27 cubic feet, commonly used to order concrete, gravel, soil, and mulch. A standard ready-mix concrete truck carries 8–10 cubic yards. Converting from cubic feet to cubic yards requires dividing by 27, which is why small projects are often measured in cubic feet while larger pours are discussed in yards.

D

Dead load→ Joist Span Calculator: The permanent, constant weight of the structure itself — including framing lumber, decking, roofing, flooring, and any fixed finish materials. Dead load is combined with live load to determine the total load a joist, beam, or column must support. Because dead load does not change, it is typically easier to calculate than live load.
Decking→ Deck Calculator: The horizontal surface boards that make up the walking surface of a deck, installed on top of the joist system. Decking is available in pressure-treated lumber, composite material, hardwood, and PVC. Board width, spacing between boards for drainage, and pattern (straight, diagonal, herringbone) all affect the total material needed.
Drywall→ Drywall Calculator: A panel made of gypsum plaster sandwiched between two layers of paper, used to create interior wall and ceiling surfaces. Standard panels are 4 feet wide and 8 or 12 feet long; thickness ranges from 3/8 inch for curved surfaces to 5/8 inch for fire-rated assemblies. Drywall is also called gypsum board, wallboard, or sheetrock (a brand name).

F

Fascia→ Deck Calculator: The horizontal board that runs along the lower edge of a roof or the outer edge of a deck, covering the ends of the rafters or joists. On a roof, the fascia is typically the surface the gutters attach to. On a deck, it gives the structure a finished appearance and hides the joist ends from view.
Flashing→ Roof Pitch Calculator: Thin sheets of metal — usually aluminum, galvanized steel, or copper — installed at joints and transitions in a roof or wall to direct water away from vulnerable areas. Flashing is used where a roof meets a wall, chimney, or vent pipe, and in valleys where two roof planes meet. Improper or missing flashing is one of the most common causes of roof leaks.
Footing→ Concrete Calculator: A concrete pad or continuous strip poured below grade to spread structural loads over a wider area of soil. Footings sit below the frost line to prevent movement from freeze-thaw cycles. Deck posts, foundation walls, and load-bearing columns all require footings sized to the load they carry and the bearing capacity of the soil.
Frost line→ Concrete Calculator: The maximum depth at which the ground is expected to freeze in a given location during winter. Footings and foundations must be placed below the frost line so that ground movement from freezing and thawing does not shift or crack the structure above. Frost depth varies widely by climate — from a few inches in the deep South to several feet in northern states and Canada.

G

Gravel→ Gravel & Mulch Calculator: Loose rock fragments used for drainage, base material, driveways, and landscaping. In construction, gravel is often used as a base layer under concrete slabs and pavers to provide drainage and a stable bearing surface. Crushed stone and pea gravel are common types; the right choice depends on the application and required drainage rate.
Grout→ Tile Calculator: A cementitious or epoxy material used to fill the joints between tiles after installation. Sanded grout is used for joints wider than about 1/8 inch; unsanded grout is used for narrower joints. Grout color significantly affects the finished look of a tile installation and can be harder to change after the fact than people expect.

H

Header: A horizontal structural member placed over a door, window, or other opening in a framed wall to carry the load from above the opening to the jack studs on either side. Header size must be sufficient for the span and the load; larger openings and heavier loads above require bigger headers. Engineered lumber headers (LVL or PSL) allow longer spans with less depth than solid lumber.
Hip roof→ Roof Pitch Calculator: A roof style where all four sides slope downward toward the walls, meeting at a ridge at the top and at hips (diagonal lines) at the corners. Unlike a gable roof, a hip roof has no vertical end walls, which can make it more resistant to wind. Hip roofs require more complex framing and more roofing material than a simple gable roof of the same footprint.

J

Jack stud: A shorter stud installed alongside a king stud to support the header over a door or window opening. The jack stud carries the header load and defines the height of the rough opening. Window and door frames require a jack stud on each side of the opening; wide openings sometimes use double jack studs for added support.
Joint compound→ Drywall Calculator: A gypsum-based paste applied over drywall seams, screw dimples, and patches to create a smooth, seamless surface ready for paint. Multiple thin coats are applied and sanded between coats. All-purpose compound is the most common type; lightweight compound is easier to sand and often used for finish coats.
Joist→ Joist Span Calculator: A horizontal framing member that spans between beams or walls to support a floor or ceiling. Joists are installed parallel to each other at regular spacing — typically 12, 16, or 24 inches on center — and the floor or ceiling sheathing is fastened to them. The required size and species depends on the span, spacing, and load.

K

King stud: A full-height stud that runs from bottom plate to top plate on each side of a door or window opening. The king stud anchors the jack stud beside it and transfers loads around the opening to the plates. Unlike the jack stud, the king stud is not interrupted by the rough opening.

L

Ledger board→ Deck Calculator: A horizontal member bolted to the side of a house to support one end of deck joists, replacing the beam and posts that would otherwise be needed at that end. A ledger is typically the same size lumber as the joists it supports. Proper flashing around the ledger is critical — improper ledger installation is one of the leading causes of deck failures and rot.
Live load→ Joist Span Calculator: The variable, moveable weight on a structure — people, furniture, snow, and stored items. Unlike dead load, live load can change moment to moment. Residential floors are typically designed for 40 pounds per square foot of live load; decks are often designed for 40–60 psf. Joist span tables are based on combined dead and live load assumptions.
Load-bearing: Describes any structural element — wall, beam, column, or post — that carries weight from above and transfers it down to the foundation. Removing or modifying a load-bearing element without proper temporary support and replacement structure can cause partial or full collapse. A structural engineer or experienced contractor should confirm which elements are load-bearing before any renovation work begins.

M

Mastic→ Tile Calculator: A thick, flexible adhesive used to bond tiles to a substrate, particularly on walls. Mastic is easier to work with than thinset because it does not need to be mixed and provides some initial grab that holds tiles in place on vertical surfaces. It should not be used in wet areas like shower pans because prolonged moisture exposure can cause it to soften and fail.
Mortar→ Brick Calculator: A mix of cement, sand, and water used to bond masonry units such as brick, block, and stone. Mortar fills the joints between units and gives the finished wall its weather resistance. Different mortar types (designated Type S, N, M, etc.) have different strengths and are selected based on the application and exposure conditions.
Mulch→ Gravel & Mulch Calculator: Organic or inorganic material spread over soil to retain moisture, suppress weeds, and moderate soil temperature. Common organic mulches include wood chips, bark, and shredded leaves; inorganic options include gravel and rubber. A depth of 2–4 inches is typical for most landscape applications; deeper applications can suffocate plant roots.

N

Nominal size→ Board Feet Calculator: The size by which lumber is sold and referenced, which is larger than its actual (dressed) dimensions. A "2×4" actually measures 1.5 inches by 3.5 inches after milling and drying. Nominal sizes are used for specifying materials, but actual dimensions must be used in calculations where fit matters — framing rough openings, for example.

O

O.C. (On Center)→ Joist Span Calculator: The distance measured from the center of one structural member to the center of the next. A joist spacing of 16″ O.C. means each joist centerline is 16 inches from the adjacent one. On-center spacing is used because it accounts for the member width, keeping layout consistent regardless of lumber thickness.
OSB: Oriented strand board — a structural panel made of wood strands or flakes bonded together with adhesive under heat and pressure. OSB is widely used as wall sheathing, roof decking, and subfloor material. It is less expensive than plywood but more susceptible to edge swelling when exposed to moisture.

P

Paver→ Concrete vs. Pavers: A flat unit of concrete, brick, stone, or other material used to create a walking surface such as a patio, driveway, or path. Pavers are set on a compacted gravel base with a layer of bedding sand on top. The base depth depends on soil conditions and expected load — vehicle traffic requires a deeper and more compacted base than a pedestrian patio.
Pitch→ Roof Pitch Calculator: The steepness of a roof, expressed as the number of inches of vertical rise for every 12 inches of horizontal run. A 6:12 pitch rises 6 inches for every 12 inches of run. Pitch affects how much roofing material is needed, what types of roofing products can be used, and how quickly the roof sheds water.
Plywood: A structural panel made of thin wood veneers (plies) glued together with the grain of adjacent layers running perpendicular to each other. This cross-grain construction gives plywood good strength in all directions and resistance to splitting. Plywood is used for subfloors, sheathing, concrete forms, and cabinet carcasses.
Post→ Fence Calculator: A vertical structural member that transfers loads from beams and headers above it down to the footing or foundation below. Fence posts are set in the ground or in concrete footings and support the rails and pickets. Deck posts connect the deck structure to the footings and are a critical element for load transfer and lateral stability.
PSI→ Concrete Calculator: Pounds per square inch — the unit used to specify the compressive strength of concrete after 28 days of curing. Standard residential flatwork (slabs, sidewalks) typically calls for a 3,000–4,000 PSI mix; foundations and driveways often use 4,000 PSI. Higher PSI mixes contain more cement and are more resistant to cracking, freeze-thaw damage, and surface wear.

R

R-Value: A measure of thermal resistance — how well a material slows the transfer of heat. Higher R-values mean better insulation performance. Building codes specify minimum R-values for walls, ceilings, and floors based on climate zone; the required values are higher in colder climates. R-values of different insulation layers in a wall assembly can be added together for a total assembly R-value.
Rafter→ Roof Pitch Calculator: A sloped framing member that runs from the ridge at the peak of a roof down to the wall top plate or eave. Rafters carry the weight of the roofing material, snow, and wind loads and transfer them to the walls. Common rafters run perpendicular to the ridge; hip and valley rafters run diagonally and require different length and angle calculations.
Ridge board→ Roof Pitch Calculator: The horizontal board at the peak of a traditionally framed roof to which the upper ends of rafters are nailed. The ridge board itself is not a structural beam in conventional rafter framing — the opposing rafters push against each other through the ridge board and the ceiling joists act as ties to prevent the walls from spreading outward. In ridge beam systems, the ridge is structural and must be supported at each end.
Rise→ Stair Calculator: The total vertical height a staircase climbs from one floor level to the next. Total rise is divided into equal increments (individual risers) during stair layout. Building codes limit the maximum height of each riser — typically 7 to 7-3/4 inches — to ensure stairs are safe and comfortable to climb.
Riser→ Stair Calculator: The vertical face of a stair step — the piece between one tread and the next. Riser height is the measurement from the top of one tread to the top of the next; all risers in a flight must be within 3/8 inch of each other per most building codes. Open-riser stairs have no vertical riser board; they require the horizontal gap between treads to meet code limits.
Run→ Stair Calculator: The horizontal distance a staircase travels from top to bottom, or the depth of a single step (tread depth minus nosing overhang). Total run depends on the number of steps and the individual tread depth. Code typically requires a minimum tread depth of 10–11 inches so there is enough room to place a foot comfortably.

S

Sheathing: Structural panels (plywood or OSB) applied to the outside face of wall framing or over roof rafters to provide rigidity, a nailing surface for cladding, and a weather barrier substrate. Wall sheathing transfers lateral wind and seismic forces through the framing to the foundation. Roof sheathing provides a continuous surface for fastening roofing felt and shingles.
Shim: A thin, tapered piece of wood or composite material used to fill gaps and level or plumb structural elements. Shims are commonly driven in pairs from opposite sides so the combined thickness can be adjusted precisely. They are used when installing doors, windows, and cabinets to account for out-of-level floors and out-of-plumb walls.
Sill plate: The bottom horizontal framing member of a wall, resting directly on the foundation or subfloor. The sill plate is typically pressure-treated lumber when in contact with concrete to resist moisture and decay. It is anchored to the foundation with anchor bolts and provides the base to which wall studs are nailed.
Slope→ Roof Pitch Calculator: The incline of a surface, often expressed as a ratio of vertical rise to horizontal run. Roof slope is the same as pitch. Drainage slopes — for concrete, decks, and gutters — are usually expressed in inches per foot and must meet minimum values so water does not puddle. A minimum slope of 1/4 inch per foot is common for flat or nearly flat surfaces that must drain.
Soffit: The underside of an overhanging building element — most commonly the underside of the roof eave that extends beyond the exterior wall. Soffits are typically finished with vented panels that allow air to enter the attic as part of the roof ventilation system. The term also refers to the horizontal enclosure built below upper kitchen cabinets to close the space between cabinet tops and the ceiling.
Span→ Joist Span Calculator: The unsupported distance a structural member — joist, beam, or rafter — must bridge between supports. Longer spans require larger or deeper lumber to carry the same load without excessive deflection. Span tables published by lumber associations and codes specify the maximum allowable span for each lumber species, grade, and size combination at given spacings and load conditions.
Square (roofing)→ Roof Pitch Calculator: A unit of roofing area equal to 100 square feet. Shingles, roofing felt, and metal roofing are sold by the square. To find the number of squares needed, divide total roof area (in square feet, accounting for pitch) by 100 and add a waste factor for hips, valleys, and starter courses.
Stringer→ Stair Calculator: The diagonal side board of a staircase that supports the treads and risers. A closed stringer has treads and risers housed into its inner face; an open stringer has the tread profile cut out of the top edge, leaving the tread ends visible from the side. Most residential stairs have two stringers — one on each side — with an optional center stringer for wide stair widths.
Stud: A vertical framing member in a wall that runs between the bottom plate and top plate, providing support for sheathing, drywall, and any load above the wall. Standard stud spacing is 16 inches on center, though 24 inches on center is allowed for some applications. Studs are typically 2×4 for interior walls and 2×6 for exterior walls where more insulation is required.
Subfloor→ Flooring Calculator: The structural panel layer fastened to floor joists, forming the base for finished flooring materials like hardwood, tile, vinyl, or carpet. Subfloor is typically 3/4-inch tongue-and-groove plywood or OSB. Subfloor panels are both glued and nailed (or screwed) to joists to minimize squeaking. The finished flooring is installed on top of the subfloor, sometimes with an underlayment in between.

T

Thinset→ Tile Calculator: A cement-based adhesive mortar used to bond tile to floor and wall substrates, mixed with water or a latex additive. Thinset is the standard setting material for most floor tile installations and anywhere moisture is a concern, including shower walls. The term comes from the thin layer used compared to older thick-bed mortar methods.
Tread→ Stair Calculator: The horizontal surface of a stair step — the part you step on. Tread depth (also called run) is measured from the front edge (nosing) to the riser face of the next step. Building codes specify minimum tread depths to ensure that a foot can be placed flat on the step, and all treads in a flight must be consistent in depth.

U

Underlayment→ Flooring Calculator: A layer of material installed between the subfloor and the finished flooring to provide a smooth surface, cushioning, moisture protection, or sound reduction. Roofing underlayment (felt or synthetic) serves a different purpose: it acts as a secondary water barrier under shingles. For flooring, the type of underlayment needed depends on the finished floor material and subfloor condition.

V

Valley (roof)→ Roof Pitch Calculator: The internal angle formed where two roof planes meet, creating a low point where water from both planes flows together. Valleys are high-traffic water zones and must be carefully flashed to prevent leaks. Open valleys leave the metal flashing exposed; closed valleys weave shingles across the intersection or use one plane of shingles over the other.
Vapor barrier: A material — typically plastic sheeting — installed to resist the diffusion of moisture through walls, floors, and ceilings. Vapor barriers are placed on the warm side of insulation (inside the insulation in cold climates) to prevent warm interior air from carrying moisture into the wall cavity where it can condense. Improper placement or use of vapor barriers can trap moisture in an assembly and accelerate rot.

W

Waste factor→ Flooring Calculator: A percentage added to the calculated material quantity to account for cuts, defects, breakage, and pattern matching during installation. A 10% waste factor is common for straight-lay flooring; diagonal or herringbone patterns may need 15–20% extra because more material is cut away at walls and corners. Ordering without a waste factor risks running short mid-project.