Every field has its jargon, and home repair and DIY projects is worse than most. This glossary covers the 36 terms that come up again and again in our guides and in the questions readers send us. Definitions are short on purpose: enough to unblock you, with links to deeper guides throughout the site when you want the full story.

Caulk

A flexible sealant material used to fill gaps and cracks between surfaces like trim and walls. It prevents air and water from leaking through seams and comes in silicone or acrylic varieties. Caulk is typically applied with a caulking gun.

Drywall

A lightweight building material made of gypsum plaster sandwiched between paper layers, used to create interior walls and ceilings. It’s also called plasterboard or gypsum board. Drywall is easy to install and repair for DIYers.

Flashing

Thin metal or rubber material installed to prevent water from entering gaps where different building materials meet, such as where a roof meets a chimney. Proper flashing is essential for preventing water damage. It’s commonly found around windows, doors, and roof penetrations.

Grout

A cement-based material used to fill spaces between tiles on floors, walls, or countertops. It hardens and helps hold tiles in place while preventing moisture from seeping underneath. Grout comes in sanded and unsanded varieties depending on the gap size.

A horizontal structural beam that spans above a door or window opening to support the weight of the wall above it. Headers are essential for maintaining the structural integrity of a wall. Larger openings require bigger, stronger headers.

Insulation

Material installed in walls, attics, or crawl spaces to reduce heat transfer and improve energy efficiency. Common types include fiberglass batts, blown cellulose, and foam boards. Proper insulation helps keep your home warm in winter and cool in summer.

Joint Compound

A putty-like substance used to fill seams between drywall sheets and to cover drywall fasteners. It’s applied in layers and sanded smooth to create an even surface ready for painting. Also called mud or spackling compound.

Joist

A horizontal wooden beam that supports floors or ceilings and distributes weight evenly. Joists are typically spaced 16 or 24 inches apart. They run perpendicular to the direction of the span they support.

Leveling

The process of making a surface perfectly horizontal or at a specific angle using a level tool. Leveling is critical for projects like installing shelves, cabinets, or flooring. Proper leveling prevents doors from swinging open or items from sliding.

Linseed Oil

A natural oil derived from flax seeds used to finish and protect wood surfaces. It penetrates the wood grain to enhance color and provide water resistance. Linseed oil requires periodic reapplication unlike some synthetic finishes.

Load-Bearing Wall

A wall that supports structural weight from above, such as joists, rafters, or another story of the home. Load-bearing walls cannot be removed or significantly altered without proper structural support like a beam. Never remove a load-bearing wall without consulting a structural engineer.

Mortar

A mixture of cement, sand, and water used to bind bricks or stones together in masonry projects. Mortar joints between bricks can fail over time and require repointing. Different mortar types have varying strength and flexibility.

Nail Pop

When drywall nails or screws push through the drywall surface, creating a visible bump or hole. Nail pops happen as wood framing dries and shrinks after initial construction. They can be fixed by driving the fastener deeper and covering with joint compound.

Outlet

A wall receptacle that provides electrical power to plug in devices and appliances. Standard outlets have two vertical slots and a round ground hole. GFCI outlets provide extra protection against electrical shock in wet areas like kitchens and bathrooms.

Patching

The process of repairing damage to walls, ceilings, or other surfaces by filling holes or cracks. Small holes are patched with spackling compound while larger areas may need drywall patches. Patched areas are typically sanded and painted to blend with surrounding surfaces.

Pitch

The slope or angle of a roof, typically expressed as a ratio like 4:12 meaning 4 inches of rise for every 12 inches of horizontal run. A steeper pitch sheds water and snow better but is more difficult to work on. Pitch is important for determining proper drainage and material selection.

Primer

A coating applied to surfaces before painting to improve paint adhesion and provide better coverage. Primer is especially important on new drywall, wood, or when covering stains and dark colors. Using proper primer helps paint last longer and look more professional.

Rafter

A sloped structural beam that forms the framework of a roof and supports roof sheathing and shingles. Rafters run from the ridge of the roof down to the eaves. The spacing and size of rafters depends on roof pitch and snow load requirements.

Rough-In

The stage of construction where structural framing, electrical wiring, plumbing, and HVAC are installed before walls are closed up. A rough-in inspection typically happens before drywall installation. Getting rough-in work inspected ensures it meets building codes.

R-Value

A measure of insulation’s ability to resist heat transfer, with higher numbers indicating better insulation performance. Different climates require different R-values for adequate energy efficiency. The needed R-value varies depending on whether you’re insulating walls, attics, or basements.

Sanding

The process of using sandpaper or a sanding tool to smooth rough surfaces like drywall or wood. Sanding is typically done after spackling or painting to create a smooth finish. Different grit sandpapers are used for different stages, from coarse to fine.

Sealant

A material applied to surfaces to prevent moisture, air, or pest infiltration. Sealants are used around windows, doors, pipes, and other openings. Common sealants include caulk, weatherstripping, and expandable foam.

Sheathing

The layer of boards or panels fastened to roof rafters or wall studs that provides structural support and a base for exterior coverings. Roof sheathing supports roofing materials while wall sheathing provides bracing. Sheathing is typically made from plywood or oriented strand board (OSB).

Shim

A thin wedge-shaped piece of material used to fill small gaps and level components like doors, windows, or cabinets. Shims help ensure doors and windows open and close properly. They’re commonly made from wood or plastic.

Soffit

The underside of an overhang or eave, the area beneath the roof edge where it extends past the wall. Soffits often contain ventilation holes to allow air circulation in the attic. They protect the underside of the roof structure from weather and pests.

Stud

A vertical wooden or metal framing member that forms the skeleton of walls. Studs are typically spaced 16 or 24 inches apart and run from the floor to the ceiling. Studs provide structural support and attach drywall to the frame.

Subfloor

The structural layer of boards or plywood installed directly on floor joists beneath the finished flooring. The subfloor provides support and distributes weight across joists. It must be properly fastened to prevent squeaking and movement.

Taping

The process of applying joint tape and joint compound over drywall seams to create smooth, invisible transitions. Taping requires multiple coats of compound, with sanding between each coat. Proper taping technique is essential for a professional-looking drywall finish.

Texture

A surface finish applied to drywall or plaster to hide imperfections and add visual interest. Common textures include popcorn, orange peel, and knockdown finishes. Textured surfaces can be harder to repair and clean than smooth drywall.

Trim

The molding installed around doors, windows, baseboards, or ceilings to create finished edges and hide gaps. Trim is typically made from wood, MDF, or vinyl. Trim pieces come in various profiles and can be stained, painted, or left natural.

Underlayment

A protective layer installed beneath flooring, roofing, or other materials to provide moisture protection and create a smooth surface. Different underlayments are used for different applications, such as cork under hardwood or tar paper under roofing. Underlayment helps prevent squeaking, buckling, and water damage.

Ventilation

The system that allows fresh air to enter a home and stale air to exit, including exhaust fans and passive air flow. Good ventilation prevents moisture buildup and improves indoor air quality. Attics, crawl spaces, and bathrooms require proper ventilation.

Wallboard

Another term for drywall, the gypsum-based material used to create interior wall and ceiling surfaces. Wallboard is available in different thicknesses and fire-resistance ratings. It’s typically installed in sheets that are then taped, mudded, and painted.

Weatherstripping

Strips of material like foam, rubber, or vinyl applied around doors and windows to prevent air and water infiltration. Weatherstripping degrades over time and may need periodic replacement. It’s an inexpensive way to improve energy efficiency.

Wire Gauge

A measurement of electrical wire thickness, with lower numbers indicating thicker, higher-capacity wire. Proper wire gauge must be matched to circuit breaker amperage for safety. Using undersized wire can cause overheating and fire hazards.

Zoning

Dividing a home’s HVAC system into separate areas that can be heated or cooled independently. Zoning allows different rooms to be maintained at different temperatures. Zone dampers in ductwork control airflow to each zone.