How Much Plywood for a 24x24 Garage Floor?

How that number is worked out

These are the figures this page was built with and every line the calculator produces from them. Change anything above and all of it moves.

Floor size compared

The standard twenty four foot wide garage depths. The joist column grows faster than the sheet column, because joists are priced by the foot and sheets by the sheet.

What else matters here

Twenty sheets, 432 ft of joist and 6 tubes of adhesive. Twenty four by twenty four is the standard two car garage footprint, and it is the cleanest dimension pair on this whole list: 24 is three sheets on their short edge or two sheets long plus one short, with no waste cut in either direction.

The area is exactly 18 sheets bare, so the twenty includes two for waste, and at this size they will be used. A floor this big has enough joints that one sheet somewhere will be cut twice.

The thing nobody plans for is handling. Twenty sheets of three quarter inch plywood is most of a pickup bed and well beyond what two people carry comfortably one at a time across a site. Have them delivered and dropped as close to the deck as the truck can get, keep them flat and off the ground on bearers, and cover them. A sheet that sits on wet ground on its edge for two days will not lie flat again, and a floor sheet that will not lie flat is a squeak you have already built in.

What this calculator assumes

• A sheet is 4 by 8, which is 32 square feet, so three and an eighth sheets cover a square.
• Openings come off in full here, not at half. A window hole in a sheathed wall is a real hole and the offcut around it is what the waste line is for.
• The nail count is the fastener schedule rather than a rule of thumb: six inches around every edge and twelve inches into the framing in the field, so a sheet at 16 inch spacing takes 64 nails and one at 24 inch spacing takes 56. Eight penny common runs about 100 nails to the pound.
• Subfloor adhesive is figured on the linear feet of joist under the sheets, at about 84 feet of quarter inch bead from a 28 ounce tube, which is the size subfloor adhesive actually comes in.
• Roof sheathing wants H clips in each bay along the unsupported joint between rafters, which is four per sheet at 24 inches on center. At 16 inches most panel thicknesses do not need them, so the list leaves them off below 19.2 inch spacing.
• A subfloor gets screwed rather than nailed on most jobs, so the list carries the same fastener count in number eight screws at about ninety five to the pound and leaves the nail line under it as the alternative. Only one of those two lines gets bought.
• Thickness does not change the count, only the price and the span rating. Check the panel span rating against your framing spacing before you buy the thin one.

Questions people ask

Other common sizes