Hanging
Screws per sheet: spacing, length and pounds
Screws are cheap, but a wrong count means a second trip and a wrong spacing means nail pops. The count is a small piece of arithmetic anyone can check.
The spacing rule
The Gypsum Association’s application standard, GA-216, sets the maximum distance between fasteners along each stud or joist. For screws on a single layer of board:
| Where | Framing 16 in apart | Framing 24 in apart |
|---|---|---|
| Walls | 16 in | 12 in |
| Ceilings | 12 in | 12 in |
| Walls with adhesive | 24 in | 24 in |
| Ceilings with adhesive | 16 in | 16 in |
Nails go closer: 8 in on walls and 7 in on ceilings. Every fastener sits at least 3/8 in from the edges and ends of the sheet, driven just below the surface without tearing the face paper. The full table, with fasteners per sheet for every size, is on the fastener spacing table.
Counting screws on one sheet
A sheet hung horizontally crosses the studs. Each stud it crosses gets a line of screws, and each line has screws at the spacing along it, the first and last near the edges.
A 4 × 8 sheet on a wall with studs at 16 in crosses 96 ÷ 16 + 1 = 7 studs, with 48 ÷ 16 + 1 = 4 screws on each: 28 screws. On a ceiling at 12 in spacing it is 7 × 5 = 35. A 4 × 12 sheet takes 40 on a wall and 50 on a ceiling. The screw spacing pattern calculator draws the pattern for any sheet and framing.
Many hangers screw walls at 12 in out of habit, which is 35 screws per 4 × 8 sheet. It does no harm and costs a few more screws.
Counting a whole job
40 wall sheets and 20 ceiling sheets, studs and joists at 16 in
- Walls: 40 × 28 = 1,120 screws, plus 10% for drops and misses = 1,232
- Ceilings: 20 × 35 = 700, plus 10% = 770
- With adhesive on the walls: 21 screws a sheet, 924 for the 40 wall sheets
- At about 210 screws per pound of 1-1/4 in screws, the walls take 5.9 lb: six 1 lb boxes, or one 5 lb box and one 1 lb
The drywall screw calculator gives the count, the weight and the boxes.
Which length
A screw must go at least 5/8 in into wood framing, or at least 3/8 in through steel framing. That sets the length:
| Board | Wood studs | Steel studs |
|---|---|---|
| 1/2 in | 1-1/4 in coarse thread | 1-1/4 in fine thread |
| 5/8 in | 1-5/8 in coarse thread | 1-1/4 in fine thread |
| Two layers of 1/2 in | 1-5/8 or 2 in (face layer) | 1-5/8 in fine thread |
| Two layers of 5/8 in | 2 in (face layer) | 1-5/8 in fine thread |
Coarse threads grip wood; fine threads grip thin steel. Self-drilling screws are for heavier-gauge steel. Longer is not better: a 2 in screw in a single layer of 1/2 in board on wood framing finds wires and pipes behind the studs more easily, and drives harder. The guide to metal vs wood studs has more on fastening to steel.
Screws per pound
Drywall screws are sold by weight, so the count has to be turned into pounds. Typical box counts of #6 bugle-head screws:
| Length | Screws per pound |
|---|---|
| 1-1/4 in | about 210 |
| 1-5/8 in | about 160 |
| 2 in | about 120 |
| 2-1/2 in | about 95 |
The box always states its own count; when it does, use that. A rough rule falls out of the arithmetic: about one pound of 1-1/4 in screws per seven sheets of wall board.
Adhesive
A bead of drywall adhesive down the centre of each stud bonds the board and lets the screws in the field of the sheet open to 24 in on walls and 16 in on ceilings. The perimeter of every sheet still gets the normal spacing. On a 4 × 8 wall sheet that takes the count from 28 to 21.
Adhesive for 40 wall sheets
- Bead: 7 studs × 4 ft = 28 ft a sheet, 1,232 ft with 10% waste
- A 28 oz tube lays about 38 ft of 3/8 in bead
- 33 tubes, saving 280 screws
Adhesive is not about the screws saved: it reduces nail pops and squeaks, and it stiffens the wall. It is not allowed on some fire-rated assemblies, and never over a vapour retarder unless the tube says so. The adhesive calculator counts the tubes.
Nails
Ring-shank drywall nails are allowed by GA-216 at 8 in on walls and 7 in on ceilings, which is 49 nails on a 4 × 8 sheet against 28 screws. They are quicker with a hammer and slower to do well; they also pop more as the framing dries. The nail calculator counts them, including the double-nailing method that spaces pairs of nails 2 in apart.
Driving screws well
- Depth: just below the surface, so the head dimples the paper without breaking it. A broken face paper does not hold; drive another screw 2 in away.
- Start in the middle of the sheet and work outward, so the board lies tight to the framing.
- Hold the board tight to the stud as the screw goes in. A screw that pulls the board in from a gap will pop later.
- Miss the stud, pull the screw. A screw that missed the framing holds nothing and pops through the finish.
- A screw gun with a depth-setting nose makes all of this automatic, and rents cheaply.
When screws pop
A screw or nail head that pushes out through the finish months later is a pop. It happens when lumber dries and shrinks away from the board, or when a fastener was driven through a gap. The fix is to drive a new screw 1 to 2 in from the popped one, reset or remove the old one, and refinish the spot; the guide to drywall repairs covers it.