Paint and drywall words, explained
The calculators on this site use the words on paint cans, data sheets and drywall bundles. If a label stops you, the meaning is probably below: one line each, in plain English, with a link to where the word matters.
Buying paint
| Word | What it means |
|---|---|
| Coverage (spread rate) | How much surface one gallon (or litre) covers in one coat, printed on the can and data sheet: 350–400 sq ft per gallon on Sherwin-Williams ProMar 200, 400–450 on Benjamin Moore Regal Select, 250–400 on Behr Premium Plus. |
| Product data sheet (PDS) / technical data sheet (TDS) | The manufacturer’s spec sheet: coverage, film thickness, dry and recoat times, the recommended primer and number of coats. Search the product name plus “data sheet”. |
| Mils wet / mils dry | Film thickness in thousandths of an inch. Coverage is measured at a set wet thickness, typically about 4 mils; spread paint thinner and it covers more area but hides and wears worse. |
| Volume solids | The share of the paint that stays on the wall after the water or solvent evaporates. Higher solids generally means a thicker dry film per coat. |
| Hide | How well a coat covers the color underneath. Deep and bright colors hide less per coat, so they need more coats or a tinted primer. |
| Base (tint base) | The uncolored paint the store adds colorant to: white or pastel bases for light colors, deep and clear bases for strong ones. |
| Sheen | How shiny the dried paint is, from flat or matte through eggshell, satin and semi-gloss to gloss. See the paint sheen chart. |
| Latex / waterborne / acrylic | Water-based paints, cleaned up with water. Nearly all wall paint is latex now. |
| Alkyd / oil-based | Solvent-based paint that cures hard and levels well; used on trim and metal. Waterborne alkyds give a similar finish with water cleanup. |
| Enamel | A paint that dries hard and smooth, usually satin or glossier: the type used for trim, doors and cabinets. |
| VOC | Volatile organic compounds, the solvents that evaporate as paint dries. Data sheets give the VOC level; “zero VOC” paints still need ventilation while you work. |
| Boxing | Pouring several cans of the same color into one bucket and mixing them, so the color is identical on every wall. |
Two worked examples: how much does a gallon of paint cover explains the coverage line on the can, and how much paint for a 12x12 room turns it into gallons for a real room.
Painting
| Word | What it means |
|---|---|
| Primer | A first coat that seals porous surfaces, blocks stains and helps the finish stick. New drywall, bare wood and patches need it; the primer calculator works it out by surface. |
| Stain-blocking primer | A primer made to stop water, smoke, tannin and marker stains bleeding through the finish coat. |
| Bonding primer | A primer formulated to grip slick surfaces such as glossy paint, laminate and old oil-based trim. |
| Cutting in | Brushing a neat band of paint along ceilings, corners and trim before rolling the open wall. |
| Wet edge | Keeping the edge of the area you are painting wet as you go, so new paint blends into it without lap marks. |
| Lap marks / flashing | Darker or shinier stripes where wet paint overlapped dry paint, or where patches and joints absorb paint differently. |
| Nap | The pile length of a roller cover. Short (1/4–3/8 in) for smooth surfaces; long (1/2–3/4 in or more) for texture and rough siding. |
| Back-rolling / back-brushing | Rolling or brushing over freshly sprayed paint to work it into the surface. |
| Recoat time | How long to wait before the next coat, on the can. Cure time, when the film reaches full hardness, can be weeks. |
| Painter’s tape | Low-tack masking tape that peels off without lifting paint. Counted in the painter’s tape calculator. |
| Caulk bead | The line of caulk laid in a joint; its diameter decides how far a tube goes. See how many feet of caulk in a tube. |
Drywall
| Word | What it means |
|---|---|
| Drywall, gypsum board, Sheetrock, plasterboard | The same thing: a gypsum core between paper faces. Sheetrock is USG’s brand name; plasterboard is the UK and Australian term. |
| Tapered edge | The long edges of a sheet are slightly thinner so that the tape and compound at the joint finish flush. |
| Butt joint | Where the square-cut ends of two sheets meet. Not tapered, so harder to finish flat; stagger them. |
| Bundle | Two sheets taped face to face, the way drywall is sold. USG’s UltraLight submittal lists 2 panels per bundle. |
| Type X / Type C | Fire-resistant boards with special cores. Codes require them in some places, such as a garage ceiling with habitable rooms above (IRC R302.6). |
| Lightweight board | Drywall with a lighter core: USG’s UltraLight 1/2 in board is about 1.25 lb per sq ft against about 1.6 for regular. |
| On center (o.c.) | Framing spacing measured from the center of one stud or joist to the next: usually 16 or 24 in. |
| Type W screw | The bugle-head screw for fastening drywall to wood framing; USG lists 1-1/4 in for single-layer 1/2 in board. |
| Joint compound (mud) | The paste used to embed tape and fill joints. All-purpose does everything; lightweight sands easier; setting-type (hot mud) hardens chemically. |
| Joint tape | Paper (or fiberglass mesh) tape bedded over joints and inside corners. USG’s estimate is 370 ft per 1,000 sq ft of board. |
| Corner bead | Metal, vinyl or paper-faced strips that protect outside corners. See the corner bead calculator. |
| Levels of finish (GA-214) | A scale from Level 0 (no finish) to Level 5. Level 4 is the usual for painted walls; Level 5 adds a skim coat over everything for gloss paints or harsh light. |
| Skim coat | A thin coat of compound over a whole surface. USG says there is no set thickness for it; see the skim coat calculator. |
| Popcorn (acoustic) texture | A sprayed ceiling texture. Old ones may contain asbestos; don’t scrape before testing. |
The drywall numbers, per sheet: how much mud per sheet of drywall, how much drywall tape per sheet and how many drywall screws per 4x8 sheet.
Wallpaper and sundries
| Word | What it means |
|---|---|
| Single roll / double roll | US wallpaper is often priced per single roll but sold in double rolls, about 20.5 in × 33 ft (56 sq ft). |
| European roll | About 0.53 × 10 m (5.3 m², 57 sq ft). |
| Pattern repeat | The distance before the pattern repeats down the roll. Each strip is cut about one repeat longer than the wall so the pattern can be lined up, which wastes paper. |
| Straight match / drop match | Straight: the pattern lines up across strips at the same height. Drop: it steps down by half a repeat on alternate strips. |
| Drop (strip) | One full-height length of wallpaper cut from the roll. |
| Spray coverage per can | The square feet a can of spray paint covers per coat, printed on the can; counted in how many cans of spray paint for a chair. |
Safety words
- RRP (Renovation, Repair and Painting) rule: EPA’s rule for work that disturbs paint in homes built before 1978. See lead paint safety.
- HEPA vacuum: a vacuum with a high-efficiency particulate filter, which traps fine dust that ordinary vacuums blow back out.
- N-100 / P100 respirator: a respirator filter class that EPA’s do-it-yourself lead guidance names; also suits drywall sanding dust.
- SDS (safety data sheet): the manufacturer’s sheet on hazards, protective equipment and first aid for a product such as joint compound.
Frequently asked questions
Is drywall the same as Sheetrock?
Yes. Sheetrock is USG’s brand of gypsum board; drywall, gypsum board, wallboard and plasterboard are general names for the same kind of panel.
What does coverage on a paint can mean?
The area one gallon covers in one coat at the manufacturer’s test thickness, on a smooth, sealed surface. Divide by the number of coats you plan.
Sources
- Sherwin-Williams, ProMar 200 Zero VOC Interior Latex Eg-Shel (B20 series), product data sheet (opens in a new tab) — Coverage 350–400 sq ft per gallon at 4 mils wet; two coats over primer on drywall; sheen 15–20 units at 85°.
- Benjamin Moore, Regal Select Interior Eggshell (549), technical data sheet (opens in a new tab) — Coverage 400–450 sq ft per gallon at 3.8 mils wet; two coats for full color; eggshell 15–22 units at 85°.
- Behr, Premium Plus Interior Flat Paint (No. 1050), technical data sheet (opens in a new tab) — Coverage 250–400 sq ft per gallon depending on application method and substrate porosity; does not include spray loss.
- USG, How to Install and Finish Sheetrock Brand Gypsum Panels (J371) (opens in a new tab) — Panel coverage table; per 1,000 sq ft of panels: 2.7 lb of Type W screws (12 in on ceilings, 16 in on walls), 5.3 lb of nails, 370 ft of joint tape, about 10 gal of All Purpose or 9 gal of Plus 3 compound; First Coat primer at 400 sq ft/gal.
- USG, Wallboard catalog (WB2816) (opens in a new tab) — Approximate weights for design and shipping: 1/4 in 1.2, 3/8 in 1.4, 1/2 in UltraLight 1.25, 1/2 in Firecode C 2.0, 5/8 in Firecode X 2.2 lb/sq ft; 48 and 54 in widths. Moisture- and mold-resistant (Mold Tough) panels: “when risk of moisture exposure is present, choose products and systems that offer adequate resistance against mold growth.”
- USG, Finishing and Decorating Gypsum Panels white paper (J2010) (opens in a new tab) — Level 5 finish: skim coat of conventional-weight All Purpose compound, then First Coat primer; “there is no specific mil thickness that constitutes a proper skim coat”.
- US EPA, Lead Renovation, Repair and Painting Program Rules (opens in a new tab) — Covers homes, child care facilities and kindergartens built before 1978; firms and renovators must be certified.