NCCER Drywall cheat sheet

Standard panel sizes: 4 ft wide by 8, 10, or 12 ft long; thicknesses of 1/4, 3/8, 1/2, 5/8 in.; 5/8 in. Type X is the common fire-rated choice.

Panel weight estimate: 1/2 in. regular board weighs about 1.6 lb per sq ft, so a 4x8 sheet is roughly 51 lb; 5/8 in. Type X runs about 2.2 lb per sq ft.

Fastener spacing on ceilings is 7 in. on center and on walls 8 in. on center for single-layer screw attachment; space fasteners 12 in. on center when panels are applied with adhesive.

Screws must penetrate at least 5/8 in. into wood framing; keep screws at least 3/8 in. from panel edges and drive heads just below the surface without breaking the paper.

Fastener spacing along panel edges and ends is 7 in. on center for ceilings and 8 in. on center for walls; intermediate framing gets the same spacing unless adhesive is used.

Stagger end joints between adjacent rows and offset them from the joints of the opposite face; butt joints should land on framing and be tight but not forced.

Leave a 1/2 in. gap between the panel edge and the floor for expansion; hold panels 1/4 in. from abutting walls and other non-framed surfaces.

For ceilings, run panels perpendicular to framing and use the longest practical length to reduce end joints; back-block butt joints that fall between framing members.

Double-layer (two-ply) systems: offset the face-layer joints at least 10 in. from the base-layer joints and use longer screws so the face layer is independently anchored.

Joint compound drying: setting-type (hot mud) cures chemically in 20-90 min depending on the product; drying-type (lightweight all-purpose) needs roughly 24 hr per coat under normal conditions.

Joint levels: Level 1 tape only, Level 2 tape plus one coat, Level 3 tape plus two coats, Level 4 tape plus three coats, Level 5 Level 4 plus a skim coat over the entire surface.

Tape joints with a thin bed of compound; paper tape is embedded and excess compound is wiped so the tape is tight, then feathered with successive wider coats.

Feather each coat 2-4 in. wider than the previous coat; typical knife widths are 4-6 in. for the bed coat, 8-10 in. for the second, and 10-12 in. for the final coat.

Corner bead: apply compound to both flanges, press the bead into place, and fasten every 9-12 in.; nails or screws must not protrude past the bead nose.

Interior corners are finished with paper tape folded at the crease; coat one side at a time and keep the opposite flange clean to avoid buildup.

Sanding sequence: 120-150 grit for rough knockdown, 180-220 grit for final smoothing; sand with light pressure and a bright side light to reveal ridges.

Prime bare compound and paper before painting; use a drywall-specific primer because compound is more absorbent than the paper facing.

Texture matching requires the same compound consistency, nozzle, air pressure, and spray distance; test on scrap board before applying to the wall.

Wood stud spacing for drywall is typically 16 in. or 24 in. on center; panels must be oriented so long edges fall on framing.

Studs must be straight and plumb within 1/4 in. in 8 ft; plane or shim high spots and sister bowed studs before hanging board.

Framing tolerance: ceiling joists and studs should be aligned so the finished plane varies no more than 1/4 in. in 10 ft.

Backing is required at all panel edges that do not land on framing; install blocking or a continuous nailer at butt joints and around openings.

Resilient channel is fastened perpendicular to joists at 24 in. on center, with screws no longer than 1 in. so they do not contact the framing; leave a 1/2 in. gap at wall intersections.

Control joints are placed in ceilings and walls longer than 30 ft, at intersections of dissimilar substrates, and where framing changes direction.

Moisture-resistant board belongs in bathrooms and behind tile; cement board is used in wet areas such as shower surrounds and tub decks.

Type X gypsum board is 5/8 in. thick with a gypsum core reinforced with glass fibers; it is used where a fire-resistance rating is required.

Install blocking for cabinets, grab bars, and heavy fixtures before closing the wall; note the location on the framing for later reference.

Drywall dust contains silica and gypsum; wear an N95 or P100 respirator during sanding and keep the work area ventilated.

Lifting limits: a 4x8 sheet of 1/2 in. board weighs about 51 lb; use a drywall lift for ceilings and two-person carries for long panels.

Ladder safety: maintain three points of contact, keep the belt buckle between the side rails, and set the ladder at a 4:1 base-to-height ratio.

Use a drywall lift or deadman for ceiling panels; never stand on buckets, sawhorses, or stacked material to reach overhead work.

Cut-resistant gloves and eye protection are required when scoring, snapping, and routing board with a utility knife.

Keep walkways clear of offcuts and loose screws; screws and staples on the floor are a common puncture and trip hazard.

Scaffold platforms must be fully planked and have guardrails at 42 in. plus midrails; never climb the cross braces.

Store panels flat on level blocking, not leaning against walls; leaning stacks can fall and warp the board.

Use a GFCI-protected circuit for power tools in wet or damp areas and inspect cords for damage before each use.