Estimating 3-tab shingles
The 3-tab is the shingle the catalog ships with: 12 inches wide, 6-inch exposure, 3-inch stagger, 8-inch minimum piece. Everything on this page follows from those four numbers.
The takeoff: courses laid every 6 inches up each facet, offset 3 inches each course, cut at every rake, hip and valley, pieces under 8 inches scrapped; the pieces counted into squares and bundles; starter and cap by the foot; underlayment, flashings, accessories and labor as for any shingle roof.
Worked example: a 40 × 30 gable at 6/12
| Item | How it is figured |
|---|---|
| Facets | Two, each 40 ft along the eave and 15 ft of flat run, 16.77 ft on the slope at 6/12. |
| Courses per facet | 16.77 ft × 12 ÷ 6 in exposure = 34 courses, the last one under the ridge cap. |
| Shingles per course | 40 ft × 12 ÷ 12 in = 40 shingles, with the rake pieces cut by the stagger: 3 in, 6 in, 9 in off the first shingle in turn. |
| Starter | 80 ft of eave. |
| Ridge cap | 40 ft of ridge. |
| Squares to buy | The counted pieces ÷ the shingles per square, with the rake offcuts in. On a gable this lands close to the area, 13.4 squares plus the cuts; on a hip roof it does not. |
On a hip roof every course on every facet ends in an angled cut, and that is where the layout earns its keep: the offcut from the left hip rarely fits the right one, and a course near the top of a hip facet is one or two shingles long with a cut on each end.
Everything else on the ticket
- Flashings from the marked lines: drip edge on eaves and rakes, valley metal, step flashing at sidewalls, headwall flashing, transition flashing at pitch breaks, each at true length.
- Underlayment by the square with lap waste; valley ice and water; ice and water on the hips as a tick box.
- Accessories placed on the drawing: pipe boots by size, roto and off-ridge vents, dryer vents, goosenecks, skylights, chimney flashing. Nails by the box.
- Labor per square from the product, tear-off per square, drive time by the trip, dump, permit, delivery, warranty reserve, tax and markups.
The architectural shingles page covers the same path for laminated shingles. The squares calculator gives the quick area figure used in the example.
Questions
How many 3-tab shingles do I need per square?
A 3-tab shingle is 12 inches wide with a 5 to 5 5/8 inch exposure; the catalog product that ships is set at 12 wide and 6 exposure for an even layout, and you can change it. Three bundles of 3-tab cover a square. Bundles equal the squares to buy, from the laid courses, times three.
How is the stagger handled?
Each course starts offset from the one below by the stagger, 3 inches on the 3-tab in the catalog, so the cutouts step and the joints never line up. The layout follows the stagger and cuts the first and last piece of each course at the rakes, hips and valleys.
What is the minimum piece?
The shortest piece worth nailing, 8 inches on the 3-tab in the catalog. A piece shorter than that at the end of a course is scrap, and the next full shingle is counted instead.
Can 3-tab be used for hip and ridge cap?
Yes, cut into caps, which is how the catalog line for 3-tab cap works: so many feet of hip and ridge per bundle. Or add a dedicated cap product with its own coverage.
Does the app price 3-tab labor lower than architectural?
Only if you set it so. Each product carries its own install labor per square.