Construction Glossary
50+ essential construction terms every DIYer and contractor should know. From "aggregate" to "waste factor."
A
Aggregate
Sand, gravel, or crushed stone mixed with cement and water to make concrete. Fine aggregate is sand; coarse aggregate is gravel or crushed stone.
Anchor Bolt
A bolt embedded in concrete foundation used to secure the sill plate of a wood-framed wall. Also called J-bolt due to its shape.
Apron
The concrete pad at the base of a garage door or driveway entrance. Also refers to the trim board under a window sill.
B
Backer Board
A cement-based panel (like HardieBacker or Durock) used as a substrate for tile in wet areas. More moisture-resistant than drywall.
Bearing Wall
A wall that supports weight from above (roof, floor). Cannot be removed without adding proper support. Non-bearing walls only support themselves.
Board Foot
A unit of lumber volume equal to 144 cubic inches (12" x 12" x 1"). Used for pricing hardwood lumber. Abbreviation: BF or bd ft.
BTU (British Thermal Unit)
A unit of heat energy. Used to rate heating/cooling equipment. One BTU raises one pound of water by 1°F.
C
Caulk
A flexible sealant used to fill gaps and cracks. Silicone caulk for wet areas; latex/acrylic for paintable indoor joints.
Compaction
The process of densifying soil or gravel using a plate compactor or roller. Prevents settling and provides stable foundation for concrete or asphalt.
Cripple Stud
Short studs installed above a header or below a window sill to maintain standard stud spacing for attaching sheathing.
Cubic Yard
A volume measurement equal to 27 cubic feet. Standard unit for ordering concrete, mulch, topsoil, and gravel.
Cure
The chemical process by which concrete gains strength. Concrete reaches full strength after 28 days. Keep moist for best results.
D
Drip Edge
Metal flashing installed at roof edges to direct water away from fascia and into gutters. Required by most building codes.
Drywall (Sheetrock, Gypsum Board)
Panels made of gypsum plaster between paper facings. Standard interior wall finish. Common sizes: 4x8 or 4x12, 1/2" or 5/8" thick.
E
Eave
The lower edge of a roof that overhangs the wall. Protects walls from rain and provides ventilation intake for attics.
Expansion Joint
A gap between concrete sections that allows for thermal expansion without cracking. Filled with compressible material.
F
Fascia
The vertical board attached to rafter ends at the eave. Gutters are typically mounted to the fascia.
Flashing
Metal or membrane material used to prevent water intrusion at roof joints, chimneys, windows, and where different materials meet.
Footer (Footing)
The concrete base that supports foundation walls or piers. Wider than the wall above to distribute weight over a larger soil area.
Furring Strip
Thin wood or metal strips attached to walls or ceilings to create a level surface for finishing materials.
G
Grade
The ground level around a building. "At grade" means at ground level. Grading refers to shaping land for drainage.
Green Board
Moisture-resistant drywall with green paper facing. For use in bathrooms and kitchens, but NOT for direct water contact like shower surrounds.
Grout
Cement-based material used to fill gaps between tiles. Available in sanded (for gaps >1/8") and unsanded varieties.
H
Header
A horizontal beam above doors and windows that transfers weight to jack studs on either side. Size depends on span and load above.
Hip
The external angle where two sloping roof surfaces meet. A hip roof has slopes on all four sides.
J
Jack Stud
A shortened stud that supports a header beside a door or window opening. Also called a trimmer stud.
Joist
Horizontal framing member that supports floors or ceilings. Typically 2x8, 2x10, or 2x12 lumber spaced 16" on center.
Joint Compound (Mud)
Gypsum-based paste used to finish drywall joints and cover screw heads. Applied in multiple coats and sanded smooth.
L
Ledger Board
A horizontal board attached to a building's rim joist to support deck joists. Must be properly flashed and lag-bolted.
Linear Foot
A measurement of length only (not width or thickness). Used for pricing trim, molding, and linear materials.
Load-Bearing
A structural element (wall, beam, column) that supports weight from above. Requires engineering to modify or remove.
LVP (Luxury Vinyl Plank)
Waterproof flooring that mimics wood appearance. More durable and water-resistant than laminate. Popular for kitchens and basements.
M
Miter
An angled cut, typically 45 degrees, used to join two pieces at a corner. A miter saw makes these cuts.
Mortar
A paste of cement, sand, and water used to bond bricks, blocks, or stones. Different types (N, S, M) for different applications.
O
On Center (O.C.)
Measurement from the center of one framing member to the center of the next. Standard stud spacing is 16" O.C.
OSB (Oriented Strand Board)
Engineered wood panel made from compressed wood strands. Used for sheathing, subflooring. Less expensive than plywood.
P
Pitch (Roof)
The slope of a roof expressed as rise over run. A 6/12 pitch rises 6 inches for every 12 inches of horizontal distance.
Plumb
Perfectly vertical (straight up and down). Opposite of level (horizontal). Checked with a plumb bob or level.
PSI (Pounds per Square Inch)
A measure of compressive strength. Concrete is rated in PSI - residential typically uses 3000-4000 PSI.
Pressure-Treated Lumber
Wood infused with preservatives to resist rot and insects. Required for ground contact and outdoor applications.
R
Rafter
Sloped framing members that form the roof structure, running from ridge to eave. Support sheathing and roofing materials.
Rebar (Reinforcing Bar)
Steel bars placed in concrete to provide tensile strength. Concrete is strong in compression but weak in tension.
Ridge
The highest horizontal line of a roof where two sloped surfaces meet. Ridge cap shingles cover this joint.
Rim Joist
The outermost joist that runs perpendicular to floor joists, forming the perimeter of the floor frame.
R-Value
A measure of thermal resistance (insulation). Higher R-value = better insulation. R-13 for walls, R-38+ for attics in most climates.
S
Sheathing
Panels (plywood or OSB) attached to wall studs or roof rafters. Provides structural rigidity and a nail base for siding/roofing.
Sill Plate
The bottom horizontal member of a wall frame that sits on the foundation. Typically pressure-treated wood bolted to concrete.
Soffit
The underside of the roof overhang. Often vented to allow air into the attic for proper ventilation.
Square (Roofing)
A unit of roof area equal to 100 square feet. Used for estimating roofing materials. 3 bundles typically = 1 square.
Stud
Vertical framing member in a wall. Typically 2x4 or 2x6 lumber spaced 16" on center.
Subfloor
The structural floor surface (plywood or OSB) attached to floor joists. Finish flooring is installed on top.
T
Thinset
Cement-based adhesive used to bond tile to substrate. Modified thinset contains polymers for better adhesion and flexibility.
Toe-Nail
Driving a nail at an angle through one piece into another, typically to attach studs to plates.
Top Plate
The horizontal framing member at the top of a wall. Double top plates provide overlap for strength at corners and intersections.
Truss
A pre-fabricated triangular roof framing assembly. Faster to install than stick-built rafters but cannot be modified.
U
Underlayment
Material installed between subfloor and finish floor (for flooring) or between sheathing and shingles (for roofing).
V
Valley
The internal angle where two roof slopes meet. Water concentrates in valleys, requiring careful flashing.
Vapor Barrier
Material (usually polyethylene sheeting) that prevents moisture from passing through walls or slabs. Placement depends on climate.
W
Waste Factor
Extra material (typically 5-15%) added to account for cutting, mistakes, and damage. Higher for complex patterns or shapes.
Weep Hole
Small opening in masonry or window frames that allows trapped water to drain out.
Wire Mesh
Welded steel grid placed in concrete slabs to control cracking. Also called welded wire fabric (WWF). Common size: 6x6 W1.4/W1.4.