Shingles & materials
Bundles per square and the waste nobody budgets for
The bundle count is easy; the waste is where orders come up short. Here is where every percent of waste goes and how to set it for your roof.
A square, a bundle, a shingle
Roofing is counted in squares: 100 square feet of roof surface. Shingles are sold in bundles, sized so a person can carry one up a ladder, and the industry settled long ago on three bundles to the square for standard products. That makes one bundle 33⅓ square feet of coverage.
The number of shingles in a bundle varies. A three-tab shingle is 12 by 36 inches and shows 5 inches to the weather, so each covers 36 × 5 = 180 square inches and a square takes 80 of them, about 26 or 27 per bundle. A typical architectural (laminated) shingle is about 13¼ by 39⅜ inches with a 5⅝-inch exposure, so each covers about 221 square inches and a square takes about 64, around 21 per bundle. Fewer shingles per square means fewer nails, which the roofing nails calculator accounts for.
When it is not three
Heavy designer and luxury shingles, the ones that imitate slate or shake with thick multiple layers, are often packed four or five bundles to the square because three bundles would each weigh over 100 pounds. The wrapper always prints the coverage, usually as “bundles per square” or “square feet per bundle”. Ordering a 4-bundle product by the 3-bundle rule leaves you a quarter short. The shingle calculator has a field for it.
| Product | Bundles per square | Coverage per bundle | Shingles per square |
|---|---|---|---|
| Three-tab | 3 | 33.3 sq ft | about 80 |
| Architectural | 3 | 33.3 sq ft | about 64 |
| Designer / luxury | 4 or 5 | 20 to 25 sq ft | varies |
| Purpose-made starter | n/a | 100 to 120 linear ft | n/a |
| Hip and ridge cap | n/a | 20 to 35 linear ft | n/a |
The shingle coverage table has the same figures with underlayment and accessories.
Where waste comes from
Waste is not carelessness. On every roof some shingle material ends up in the dumpster for reasons that are part of the job:
- Rakes. Every course ends at a gable edge with a cut shingle; the offcut can start the next course on a simple roof, but not always.
- Ridges. The top course is cut to fit under the ridge cap.
- Hips. Every course on both planes is cut on a diagonal at each hip. The offcut triangles rarely fit elsewhere.
- Valleys. Closed-cut valleys trim one plane’s shingles along the valley line; woven valleys use extra shingles to cross.
- Penetrations. Chimneys, skylights and pipes each need shingles cut around them.
- Breakage and spares. A few shingles crack in handling, and a spare bundle from the same lot is the only way to make an invisible repair later.
Estimators turn this into a percentage of the roof area.
| Roof shape | Typical waste | Why |
|---|---|---|
| Plain gable, few penetrations | 10% | Rake and ridge cuts only |
| Hip roof | 15% | Diagonal cuts on every course at four hips |
| Cut-up roof: valleys, dormers, several wings | 20% or more | Hips, valleys, dormer cheeks and short courses |
| Simple shed roof | 5 to 7% | One slope, few cuts |
Starter strip and ridge cap are not included in the field-shingle waste; they are separate products counted by length.
The arithmetic
A gable and a cut-up roof
A plain gable house: 1,977 square feet of roof (19.77 squares), 10% waste, three bundles to the square.
- 19.77 × 1.10 = 21.74 squares
- 21.74 × 3 = 65.2, rounded up to 66 bundles
A cut-up roof of 3,100 square feet with valleys and two dormers, 20% waste:
- 31 × 1.20 = 37.2 squares
- 37.2 × 3 = 111.6, rounded up to 112 bundles
On the cut-up roof the waste alone is 6.2 squares, almost 19 bundles. Both figures come from the shingle calculator.
Do not skimp, do not pad
Skimping on waste is the commonest reason for a second delivery, which costs a fee and often a half-day. Worse, a second order may come from a different production lot, and shingle colour varies slightly between lots; the patch shows for the life of the roof. Padding is less harmful but not free: unopened bundles can usually be returned, opened ones cannot, and a pallet of extra bundles is several hundred dollars.
The sensible order is the calculated figure, rounded up to whole bundles, plus nothing more. Keep the leftover from the last bundle and one unopened bundle if one remains: they are the repair stock.
Starter, cap and the edges
Two shingle products are counted by length rather than area. Starter strip runs along every eave and usually every rake; a bundle covers 100 to 120 linear feet, and the starter strip calculator counts it. Hip and ridge cap runs along the ridge and every hip; a bundle covers 20 to 35 feet depending on the product and its exposure, and the ridge cap calculator counts it. On the gable house above, two bundles of each are enough; on a hip roof the hips can triple the cap.
Checking a roofer’s squares
A roofer’s quote usually states squares with waste included. Divide it by your measured roof area in squares: a ratio of 1.10 to 1.20 means the roofer’s waste allowance matches the shape. A ratio of 1.35 means either a different measurement or a generous allowance, and it is fair to ask which. Getting your own roof area from the ground takes an hour; measuring a roof from the ground shows how, and why your roof is bigger than your house explains why the number surprises people.
Nails follow the shingles
At four nails per shingle, the nail count is four times the shingle count, which is why architectural roofs use fewer nails per square than three-tab ones. High-wind areas use six. Roofing nails and patterns covers length, placement and the box sizes, and the roof area calculator gives the area every one of these counts starts from.