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Home improvement glossary

By , Editor Last reviewed

The words you'll meet on product labels, quotes and building plans, explained plainly. Where a term has a precise technical meaning, we link the standard or agency that defines it.

68 terms

Measuring & lumber

5/4 (five-quarter)
Nominal 1¼ in thick lumber, common for deck boards. Its minimum dry dressed thickness is 1 in.Deck calculator →Source: NIST PS 20-25, American Softwood Lumber Standard
Actual (dressed) size
The finished size of lumber after drying and planing. A dry 2×4 is 1½ × 3½ in under the US lumber standard.Lumber dimensions →Source: NIST PS 20-25, American Softwood Lumber Standard
Board foot
The unit lumber volume is sold in: nominal thickness (in) × nominal width (ft) × length (ft). A 2×4 that’s 8 ft long is 5⅓ board feet.Lumber dimensions →Source: NIST PS 20-25, American Softwood Lumber Standard
Cubic yard
27 cubic feet (3 × 3 × 3 ft). Bulk concrete, mulch and gravel are ordered by the cubic yard, often just called a “yard”.Concrete calculator →
Dry lumber
Lumber seasoned or dried to a maximum moisture content of 19%. Wetter lumber is “green” and is dressed slightly larger because it shrinks as it dries.Lumber dimensions →Source: NIST PS 20-25, American Softwood Lumber Standard
Linear foot
A straight-line length of one foot, regardless of width. Trim, rails and deck boards are often priced per linear foot.
Nominal size
The name-size lumber is sold by, like “2×4”. It’s larger than the board you take home, which has been dried and planed.Lumber dimensions →Source: NIST PS 20-25, American Softwood Lumber Standard
Square foot
Area of a 1 ft × 1 ft square. Length × width in feet gives square feet.Square footage calculator →
Square yard
Area of a 3 ft × 3 ft square, equal to 9 square feet. Carpet is often priced this way.Square footage calculator →
Waste factor
Extra material bought to cover cuts, breakage and mistakes, written as a percentage on top of the measured amount.Flooring calculator →

Framing & structure

Beam
A main horizontal member that carries joists or other loads to posts or walls. Beam sizes come from span tables and local code.
Blocking
Short pieces of lumber fitted between joists or studs to stiffen the frame or give something to fasten to.
Joist
A horizontal framing member that supports a floor, deck or ceiling, set side by side at a regular spacing.Deck calculator →
Joist spacing (deck)
Decking makers such as ArmorGuard specify joists 16 in on center for boards laid straight, and 12 in for diagonal boards.Deck calculator →Source: ArmorGuard decking installation guide
Ledger board
A board fastened to a house wall that supports one end of a deck’s joists. Its attachment and flashing are critical to deck safety.Deck calculator →
Load-bearing wall
A wall that supports a load in addition to its own weight, such as floors or a roof above. Never remove or cut into one without a professional’s design and a permit.Source: HUD Building Glossary
On center (o.c.)
Spacing measured from the center of one framing member to the center of the next. “Joists 16 in o.c.” means 16 in between their centerlines.Deck calculator →
Rafter
A sloped framing member that supports a roof.
Stud
A vertical framing member in a wall, usually a 2×4 or 2×6, that drywall or sheathing is fastened to.Drywall calculator →
Subfloor
The structural layer (usually plywood, OSB or concrete) that the finished flooring sits on.Flooring selector →

Concrete & outdoor

811 (call before you dig)
The free national before-you-dig service. Contact it a few business days before digging so buried utility lines get marked.Fence calculator →Source: Common Ground Alliance, 811 Before You Dig
Bag yield
How much volume one bag makes once mixed. An 80 lb bag of QUIKRETE Concrete Mix yields about 0.60 cubic feet, so 45 bags make a cubic yard.Concrete calculator →Source: QUIKRETE Concrete Mix data sheet
Base aggregate
The compacted crushed-stone layer under pavers. ICPI gives a minimum base of 4–6 in for walks and 6–8 in for driveways.Paver calculator →Source: ICPI Tech Spec 10
Bedding sand
The screeded sand layer pavers are set on, about 1–1½ in thick per ICPI.Paver calculator →Source: ICPI Tech Spec 10
Cement vs. concrete
Cement is the powder that binds concrete. Concrete is cement mixed with sand, gravel and water. Bagged concrete mix already contains everything but the water.Concrete calculator →
Edge restraint
Edging (plastic, metal or concrete) that holds pavers in place so they don’t creep outward.Paver calculator →
Footing
The concrete base under a post, wall or foundation that spreads its load into the soil. Depth is set by local code and frost depth.Concrete calculator →
Frost line
The depth to which ground freezes in winter in your area. Footings and posts set above it can heave; your building department can tell you the local depth.Fence calculator →
Ready-mix
Concrete mixed at a plant and delivered by truck, ordered by the cubic yard.Concrete calculator →

Finishes & flooring

Acclimation
Letting flooring adjust to the room’s temperature and humidity before installing. Bruce (solid hardwood) and Pergo (laminate) require it; some engineered and vinyl products don’t.Flooring selector →
Drywall (gypsum board)
Panels of gypsum between paper faces, screwed to studs and joists to make walls and ceilings. Common sheets are 4×8, 4×10 and 4×12 ft.Drywall calculator →
Engineered hardwood
Flooring with a real-wood top layer over a layered core. Unlike solid hardwood, it can be installed below grade, such as in basements.Flooring selector →Source: NWFA, Types of wood floors
Floating floor
Flooring whose planks lock to each other rather than being nailed or glued down, like most laminate and click vinyl plank.Flooring selector →
Grout
The material that fills the joints between tiles.Flooring calculator →
Joint compound (mud)
The paste used to tape and finish drywall seams and cover screw heads.Drywall calculator →
Joint tape
Paper or fiberglass tape embedded in joint compound over drywall seams. USG gives about 370 ft of tape per 1,000 sq ft of board.Drywall calculator →Source: USG joint tape submittal
Luxury vinyl plank (LVP)
Vinyl flooring planks with a printed wood or stone look and a protective wear layer; many are waterproof.Flooring selector →
Porcelain tile
Impervious tile with water absorption of 0.5% or less, measured by ASTM C373. Ceramic tile absorbs more.Flooring selector →Source: TCNA, Porcelain tile certification
Primer
An undercoat that seals new or patched surfaces and helps paint stick and cover evenly.Paint calculator →
Sheen
How glossy paint looks when dry, from flat (no shine) through eggshell, satin and semi-gloss to gloss.Paint calculator →
Thinset
A cement-based adhesive mortar that tile is set in.Flooring calculator →
Underlayment
A thin layer between the subfloor and a floating floor that cushions, levels small dips and may block moisture. Check your flooring’s requirements.Flooring calculator →

Safety & systems

AFCI (arc-fault circuit interrupter)
A breaker or outlet that protects against fires caused by unsafe arcing in home wiring. AFCIs address fire hazards; GFCIs address shock hazards.Source: CPSC, Publication 5133 (GFCIs and AFCIs)
GFCI (ground-fault circuit interrupter)
An outlet or breaker designed to protect people from serious electric shock by cutting power when current leaks to ground. Test them monthly.Maintenance tracker →Source: CPSC, Publication 5133 (GFCIs and AFCIs)
HVAC air filter
The filter in a furnace, central AC or heat pump. ENERGY STAR says to inspect, clean or change it once a month.Maintenance tracker →Source: ENERGY STAR, Maintenance checklist
R-value
A measure of insulation’s resistance to heat flow. The higher the R-value, the better it insulates.Insulation calculator →Source: U.S. DOE, Energy Saver Guide (2022)
Smoke alarm
Test monthly, replace batteries at least yearly (unless sealed 10-year), and replace the whole alarm every 10 years, per the U.S. Fire Administration.Maintenance tracker →Source: U.S. Fire Administration, Smoke alarms
Vapor retarder (vapor barrier)
A layer in a wall, ceiling or floor that slows water vapor from entering the cavity. Class I retarders are 0.1 perm or less, Class II 0.1–1.0 perm, Class III 1.0 perm or more.Source: U.S. DOE Building Science, Vapor barriers

Roofing & insulation

Climate zone
One of the US energy-code zones, numbered 1 (hottest) to 8 (coldest). ENERGY STAR’s attic insulation recommendations are given by zone.Insulation calculator →Source: ENERGY STAR, Recommended home insulation R-values
Drip edge
Metal trim along a roof’s edges. The IRC requires it at the eaves and rakes of shingle roofs, with joints lapped at least 2 in.Roofing calculator →Source: ICC, 2021 International Residential Code, Chapter 9 Roof Assemblies
Eave
The lower, level edge of a roof, usually overhanging the wall. Starter strip, drip edge and any ice barrier run along it.Roofing calculator →
Ice barrier (ice and water shield)
A self-adhering membrane under the roofing at the eaves. Where the local code marks ice damming as a problem, the IRC requires it to reach at least 24 in inside the exterior wall line.Roofing calculator →Source: ICC, 2021 International Residential Code, Chapter 9 Roof Assemblies
Rake
The sloped edge of a roof at a gable end.Roofing calculator →
Roof pitch (slope)
How steep a roof is: inches of rise per 12 in of level run, written 6/12 or 6:12. The code sets a minimum pitch for each roofing material, such as 2:12 for asphalt shingles.Roofing calculator →Source: ICC, 2021 International Residential Code, Chapter 9 Roof Assemblies
Roof underlayment
The water-resistant layer between the roof deck and the shingles. On asphalt-shingle roofs from 2:12 up to 4:12, the IRC requires two layers.Roofing calculator →Source: ICC, 2021 International Residential Code, Chapter 9 Roof Assemblies
Square (roofing)
A 10 × 10 ft area: 100 sq ft of roof. Shingles and roofing prices are quoted per square, though for some shingles three bundles cover 98.4 sq ft.Roofing calculator →Source: GAF, What is a roofing square?

Contracts & permits

Building permit
Permission from your local building department to do certain work, usually including additions, renovations, and electrical, plumbing and HVAC work. Call your local department to ask.Renovation checklist →Source: International Code Council, Consumer safety
Change order
A written, signed change to a contract’s scope, price or schedule, agreed before the changed work is done.Renovation checklist →
Contingency
Money set aside in a budget for surprises, usually as a percentage of the estimated cost. There’s no official figure; it depends on how many unknowns the project has.Project planner →
Cooling-Off Rule
An FTC rule giving you three days to cancel many sales made at your home (not sales under $25), until midnight of the third business day.Contractor checklist →Source: FTC, The Cooling-Off Rule
Critical path
The longest chain of tasks that depend on each other in a schedule. A delay to any task on it delays the finish date.Timeline planner →
Lead-safe certified (RRP)
EPA certification required for firms doing work that disturbs paint in homes built before 1978, under the Renovation, Repair and Painting rule.Renovation checklist →Source: EPA, Lead RRP Program Rules
Lien release (lien waiver)
A signed statement that a contractor, subcontractor or supplier has been paid and gives up lien rights for that payment. The FTC suggests asking each of them for one.Contractor checklist →Source: FTC, Hiring a Contractor (PDF)
Mechanic’s lien
A legal claim against a property that secures payment for labor, materials or services used to improve it. If a contractor doesn’t pay a supplier, the supplier may be able to file one against your home, depending on state law.Contractor checklist →Source: Cornell Law LII, Mechanic’s lien
Punch list
A list of unfinished or incorrect items made during the final walk-through, to be fixed before the final payment.Renovation checklist →
Rough-in
Plumbing, electrical, gas and mechanical work put in while walls and floors are still open. The IRC requires it to be inspected before it’s covered.Timeline planner →Source: ICC, 2024 International Residential Code, R109 Inspections
Written estimate
A contractor’s written price for a job. The FTC says it should describe the work, materials, completion date and price.Contractor checklist →Source: FTC, How to avoid a home improvement scam