How Many Sheets of Plywood for 1,500 Square Feet?

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.

Roof area compared

The same roof sheathing question at every common area. The middle column is squares, the unit roofing is actually sold in, and one square is a hundred square feet.

What else matters here

Fifty two sheets, 15 squares and 1,650 sq ft of underlayment. At this size the material list is the easy part and the weather is the hard part.

Sheathing is the one stage of a build that cannot sit exposed. Panels swell at the edges when they get wet and the swelling does not fully go back, so a roof sheathed on Friday and left open over a wet weekend telegraphs every joint through the shingles for the life of the roof. The underlayment in this list is not a later trade, it is the same job: sheathe and dry in on the same day, or sheathe only as much as can be dried in that day.

The extra 150 sq ft between the roof and the underlayment figure is the ten percent for laps, and the laps are what makes it a water barrier rather than a sheet of paper. Underlayment runs from the eave up, each course lapped over the one below, so water running down the roof always meets an overlap from above rather than an edge. Laid the other way up it sheds water straight into the joint, which looks exactly the same from the ground.

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