Guide
Painting new drywall: primer and coats
One coat of primer, two of paint, and the quantities for a room.
Short answer
One coat of drywall primer, then two coats of paint. Primer goes on at about the same rate as paint, roughly 350 sq ft per gallon, so a 12 × 12 ft bedroom with 8 ft ceilings (477 sq ft of walls and ceiling) needs about 1 gallon + 2 quarts of primer and 3 gallons of paint for two coats.
Why new drywall needs primer first
Bare drywall is two surfaces, not one: the paper face and the joint compound over the seams and screws. They absorb paint at different rates, so a first coat of paint straight onto them dries unevenly and the taped joints show through as dull bands, which painters call flashing. A primer coat seals both to the same porosity. After that, the finish coats go on evenly and cover at the rate on the can.
Use a drywall primer or a PVA primer made for new board. A "paint and primer in one" is formulated to cover an already painted wall, and on bare drywall it usually needs an extra coat to do what a cheap primer does in one.
Primer and paint by room size
| Room | Surface | Primer, 1 coat | Paint, 2 coats |
|---|---|---|---|
| 10 × 10 ft | 369 sq ft | 1 gallon + 1 quart | 2 gallons + 1 quart |
| 12 × 12 ft | 477 sq ft | 1 gallon + 2 quarts | 3 gallons |
| 12 × 14 ft | 533 sq ft | 2 gallons | 3 gallons + 1 quart |
| 14 × 16 ft | 653 sq ft | 2 gallons | 4 gallons |
Quantities assume 350 sq ft per gallon, the middle of the range printed on most cans. A heavy texture or a knockdown ceiling takes noticeably more.
One coat of primer or two?
One, in almost every case. A second coat of primer is worth it in three situations: a Level 5 skim coat that is still showing through, a big patch or repair where the compound is much thicker than elsewhere, and a deep colour that the primer should be tinted toward. Two coats of primer are fine, just slower and more expensive than one coat of primer and a third coat of paint where it actually shows.
How many coats of paint after primer?
Two. One coat over primer usually looks finished at first, but it is thin enough that the roller texture and any variation in the primer show once the light moves across the wall. The second coat is what gives an even sheen. A very light colour over white primer sometimes gets away with one coat on a closet or a garage; a living space rarely does.
Will a quart of paint cover a wall?
One coat, just about: a quart covers roughly 88 sq ft, and a 10 × 8 ft wall is 80 sq ft. Two coats of the same wall need two quarts. If there are two walls to do, a gallon usually costs about the same as two quarts and leaves some for touch-ups.