NCCER Drywall key terms

A panel made of a gypsum core sandwiched between paper facings, used to cover walls and ceilings. It is sold in thicknesses such as 1/4, 3/8, 1/2, and 5/8 inch.

Gypsum board with special core additives that give it a fire-resistance rating when installed in rated assemblies. It is commonly 5/8 inch thick and must be installed exactly as the listed assembly specifies.

A wall or ceiling system tested and listed to resist fire for a stated time, such as one hour. Its rating depends on the specified board type, layers, fasteners, and framing, so substitutions can void the rating.

The distance between drywall screws along a framing member or around a panel edge. Typical interior ceilings use closer spacing than walls, and rated assemblies often require specific spacing that must be followed.

A slight recess made by driving a screw just below the board surface without breaking the paper. The dimple gives joint compound a place to cover the screw head flush with the panel.

A joint formed where two panel ends meet without tapered edges. Because there is no recess to fill, butt joints are harder to conceal and are usually finished wider than tapered joints.

A factory edge on gypsum board that slopes inward toward the face, creating a shallow recess when two panels meet. This recess accepts tape and compound so the finished joint can be made flush.

Paper or mesh strip embedded in joint compound over panel seams to reinforce them and prevent cracking. Paper tape is stronger for flat joints, while mesh tape is often used with setting-type compound.

A gypsum-based paste used to embed tape and cover joints, corners, and fasteners. It is available as drying type, which hardens as water evaporates, or setting type, which hardens by chemical reaction.

Joint compound that hardens through a chemical set rather than by drying. It is sold in powder form with a set time, such as 20, 45, or 90 minutes, and resists shrinkage better in thick fills.

The first coat of compound applied over a joint, into which the tape is pressed. It must be thin enough that excess compound does not remain under the tape and cause blisters.

Gradually thinning the edge of a compound application so it blends smoothly into the board face. Proper feathering hides the joint and reduces the sanding needed before priming and painting.

Smoothing dried joint compound with abrasive paper or mesh to remove ridges and tool marks. Over-sanding can scuff the paper facing or expose tape, so light pressure and the correct grit are important.

A sealer coat applied to finished drywall before paint. It equalizes absorption between the paper facing and the compound so the topcoat dries evenly and joints do not show through.

A metal or plastic strip fixed over outside corners to protect them and provide a straight edge for finishing. It is fastened with nails, screws, or compound and then covered with joint compound.

A corner where two wall surfaces meet at an interior angle. It is usually finished by embedding tape in compound and folding it along the crease, then coating each side separately.

Installing framing or blocking behind a panel edge that does not fall on a stud, so the edge can be fastened. It prevents loose edges and cracks at joints that lack support.

The on-center distance between wall framing members, commonly 16 or 24 inches. Panel edges must land on framing, so spacing determines how boards are laid out and cut.

A deliberate break in the drywall surface that allows movement without random cracking. It is placed in long walls and ceilings and at intersections of dissimilar building sections.

A small clearance left between panel edges and adjoining surfaces such as floors or columns. The gap allows structural movement and is later covered by trim or sealant.

A metal furring channel used to decouple gypsum board from framing and reduce sound transmission. It is screwed to framing and the board is fastened to the channel, not through it into studs.

Gypsum board with a water-repellent facing and sometimes a treated core, used in bathrooms and other damp areas. It resists moisture but is not a substitute for a waterproof shower membrane.

Planning where each board will be placed so joints land on framing and are staggered between rows. Good layout reduces waste, limits butt joints, and keeps seams away from visible focal areas.

Arranging panel seams so joints in one row do not line up with joints in the adjacent row. Staggering spreads stress and makes the finished wall stronger and easier to conceal.

A panel held against a ceiling or high wall by a mechanical lift or a helper while it is fastened. Correct positioning before fastening prevents misalignment and reduces the risk of dropped boards.

Gear worn to reduce injury, such as safety glasses, hearing protection, gloves, and a respirator for dust. Employers must provide required equipment and train workers in its proper use.

Fine airborne particles released when cutting or sanding gypsum and other materials. Repeated exposure can damage lungs, so dust controls such as wet methods, vacuum attachments, and respirators are used.

Systems and practices that prevent workers from falling from heights, including guardrails, scaffolds, and personal fall arrest. It is required when working at heights set by the applicable safety standard.

A temporary elevated platform used to reach ceilings and high walls. It must be properly supported, plumb, and equipped with guardrails, and workers must not stand on top rails or unstable objects.

Keeping the work area clean by removing scrap, sweeping dust, and storing materials safely. Good housekeeping prevents slips, cuts from sharp scrap, and dust buildup that can affect finishing quality.

A procedure that isolates hazardous energy before servicing equipment so it cannot start unexpectedly. Only authorized workers apply locks and tags, and each worker removes only their own lock.

Moving and storing panels and compound safely to avoid strain and damage. Panels should be stacked flat on supports, carried with proper lifting technique, and kept dry before installation.

A device that supports and raises panels for ceiling installation, reducing strain and improving placement accuracy. It must be assembled correctly and used on stable footing.

A cutting tool used to score and snap gypsum board. The blade should be sharp and retracted when not in use, and cuts are made away from the body to reduce injury risk.

An abrasive tool used to smooth and shape cut gypsum board edges. Rasping produces a cleaner edge for fitting and reduces the need for excessive compound at joints.

An instrument used to check moisture content in framing or finished assemblies before and after board installation. Readings help confirm that substrates are dry enough to avoid mold and finish failure.

Rusting or deterioration of nails and screws that can stain finishes and weaken attachment. Corrosion-resistant fasteners are required in damp areas and where treated or incompatible materials contact the fastener.

Using construction adhesive with fasteners to attach panels to framing. Adhesive increases stiffness and reduces fastener pops, but the correct product and application pattern must be used.