How to Shingle a Shed Roof: Bundles and Steps

To shingle a shed roof, work in a fixed order on a solid deck: drip edge at the eaves, underlayment, drip edge at the rakes, a starter course, full courses from the low edge up, then the ridge cap. Every step below comes with the number the designer counts for it and the rule the shingle makers or the model code give.

This guide starts where the shed roof guide stops: a sheathed deck. That guide covers the rafters, the fascia, the OSB and the H-clips. Here you get the bundle count for all 20 designer sheds, the underlayment choices, and the steps. If you are still deciding on the slope, read the shed roof pitch guide first, because the slope decides how much underlayment goes down.

What the deck needs before the first shingle

Shingles are only as good as what is under them. Check three things before you open a bundle: the deck, the slope and the local rules.

A solid deck first

The 2021 IRC, R905.2.1, says asphalt shingles shall be fastened to solidly sheathed decks. The designer’s roof deck is 7/16 inch OSB in 4x8 sheets, a solid deck. The model code’s span table gives a 24/16 panel at 7/16 inch a 24 inch span on the roof (2021 IRC, Table R503.2.1.1(1)), and R803.2 limits the panel overhang past a gable end wall to 9 inches unless framing supports it. The sheet layout, the H-clips and the fascia are in the how to build a shed roof guide, and the rafters are in the shed rafters guide.

Owens Corning’s Duration instructions also state a deck minimum: 3/8 inch plywood or 7/16 inch OSB, with panel gaps of 1/8 to 1/4 inch. So the designer’s OSB meets that maker’s floor. Your bundle’s wrapper sets the rule for your product.

Slope decides the underlayment

The model code allows asphalt shingles only on slopes of 2:12 or steeper (2021 IRC, R905.2.2). From 2:12 up to 4:12 it asks for double underlayment. At 4:12 or steeper one layer is enough (2021 IRC, Table R905.1.1(2), the column for areas where wind design is not required). The designer follows the same line: it offers nothing flatter than 2/12 and warns below 4/12 that two layers are needed.

ARMA’s Residential Asphalt Roofing Manual says the same in its own words. Strip shingles may go on slopes from below 4:12 down to 2:12 if special procedures are followed, and never on anything lower than 2 inches per foot.

The designer’s gable presets are 4/12 to 6/12, so they need one layer. Its four lean-to presets are 3/12, so they need two. More on that in the lean-to section below.

The makers can ask for more than the code. The lean-to section shows what CertainTeed says for slopes under 4:12.

Ice barrier and the local edition

The model code asks for an ice barrier at the eaves where the local table flags a history of ice, and it has an exception for detached accessory structures without conditioned floor area (2021 IRC, R905.1.2). A freestanding, unheated shed usually falls in that exception. A lean-to that leans on your house is not detached, so it may not. This is a model code: the locally adopted edition and its amendments decide, and the shed permits guide tells you how to check.

How many bundles of shingles a shed needs

You need a count before you shop. The designer works it out from the roof area, and the rules are simple enough to check by hand.

The designer’s counting rules

The designer counts asphalt shingles at 3 bundles per square (100 sq ft of roof), adds 10 percent for waste and rounds up. The roof area includes the overhang, which is 6 inches by default. On top of the bundles it lists:

• Starter strip: counted at 100 lin ft per bundle along the eaves. Every gable preset needs 1 bundle, from 12 lin ft on the 6x6 to 48 lin ft on the 12x24.
• Hip and ridge cap: counted at 20 lin ft per bundle along the ridge. Every gable preset needs 1 bundle except the 12x24, which needs 2.
• Underlayment: one 10-square roll of synthetic underlayment, counted with a 15 percent lap allowance.
• Drip edge: 10 ft pieces, enough for the eaves and the rakes.
• Roofing nails: 1-1/4 inch, 4 per shingle, about 320 per square.

The designer’s own output says to check the label on starter and ridge cap, because coverage per bundle varies by product.

Bundles for the 16 gable sizes

This is the designer’s result for the 16 gable presets at 6/12 with a 6 inch overhang. The first number in the size is the width across the door wall.

Two sizes show how the rounding works. The 8x12 is 1.21 squares, and 1.21 times 1.1 times 3 is 3.99 bundles, so it lists 4. The 10x10 is 1.23 squares, which comes to 4.06 bundles, so it lists 5. Two extra square feet of roof cost a whole bundle, because you round up to the next one.

Each size has its full list on its plan page, for example the 10x12 gable plan. Underlayment stays at one roll on all 16, from 0.5 squares on the 6x6 to 4.4 on the 16x20.

Bundles for the 4 lean-to sizes

A lean-to has one slope, no ridge, and no ridge cap. The designer’s four lean-to presets are 3/12 with a 6 inch overhang. Sizes are width across the door wall by depth.

Each lean-to lists 1 starter bundle (16 to 24 lin ft along the eave) and roofing nails of 2 lb on the 8x4 and 8x6, and 3 lb on the 10x8 and 12x8. The lean-to shed guide covers how these sheds go together.

What one bundle covers

The designer’s 3 bundles per square is a planning figure. Bundles differ by product, so read the coverage on the wrapper. One architectural bundle read at a Home Depot store in San Diego County, California (Otay Mesa, ZIP 92154) on September 29, 2026, the GAF Timberline Natural Shadow in Charcoal, covered 33.3 sq ft and cost $46.97, so 3 bundles is about 100 sq ft, in line with the designer. Four bundles for the 8x10 come to $187.88 at that price. That is one store on one day, and we did not find a 3-tab bundle to compare, so treat it as a snapshot and get your own price.

What goes on the deck: shingles, underlayment, drip edge and nails

Four groups of materials make the roof. Get the type right for each before you start.

Asphalt shingles for a shed roof

Asphalt shingles are the only roofing the designer counts as a shingle, and the metal roof on a shed guide covers the other option. GAF (Timberline), Owens Corning (Duration) and CertainTeed (Landmark) all give an exposure of 5-5/8 inches in the instructions we read. That means each course shows 5-5/8 inches of the shingle and hides the rest under the course above. Different products have different exposure, so the wrapper decides.

Underlayment: felt or synthetic

The 2021 IRC table describes felt (2021 IRC, Table R905.1.1(2)): one layer lapped 2 inches at 4:12 or steeper, end laps of 4 inches offset by 6 feet. ARMA’s manual says felt has historically been specified as underlayment, but that there are now many synthetic underlayments, some self-adhering. The designer counts synthetic in a 10-square roll. A synthetic roll has its own instructions for laps and fasteners, and those come from its label. If your building department has a view on synthetic, it wins.

Drip edge, starter and ridge cap

The drip edge is a metal strip along the eaves and the rakes. The model code requires one at eaves and rakes of shingle roofs, lapped at least 2 inches, reaching 1/4 inch below the sheathing and at least 2 inches back onto the deck, nailed at no more than 12 inches (2021 IRC, R905.2.8.5). The starter strip is the first row of shingle material along the eaves. The ridge cap is the cut shingle over the top. Each has its own bundle in the designer’s list.

Roofing nails

The model code says roofing nails must be galvanized steel, stainless steel, aluminum or copper, with at least a 12 gage shank and a 3/8 inch head, and they must go through the sheathing when it is under 3/4 inch thick (2021 IRC, R905.2.5). The designer’s roof deck is 7/16 inch OSB, so the nail goes through. The designer lists 1-1/4 inch nails at 4 per shingle. ARMA’s nail bulletin says the length depends on the layers under and over the deck, including underlayment and ridge caps, so check that the nail you buy clears the deck.

How to shingle a shed roof, step by step

The sequence below is general practice, with the sourced numbers in it. The instructions on your bundle override any step.

Step 1: drip edge at the eaves

1. Nail the drip edge along the eave edge first, lapping pieces at least 2 inches and nailing no farther apart than 12 inches (2021 IRC, R905.2.8.5).
2. ARMA says to apply the drip edge under the underlayment along the eaves and over it along the rakes, and the model code says the same. So the eave piece goes on before the underlayment.

Step 2: underlayment

3. Start at the low edge and work up, parallel to the eave. Lap each course 2 inches at 4:12 or steeper, and offset end laps by 6 feet (2021 IRC, Table R905.1.1(2)).
4. Below 4:12, use two layers: a 19 inch strip along the eave, then 36 inch sheets each lapping the last by 19 inches (2021 IRC, Table R905.1.1(2), and ARMA’s traditional method).
5. Fasten it the way the roll’s label says (common practice: only enough to hold it until the shingles go on).

Step 3: drip edge at the rakes

6. Nail the rake drip edge over the underlayment. How far the shingles hang past it varies by maker: GAF says not more than 1/4 inch of roof overhang, Owens Corning says the starter overhangs the drip edge by 1/4 to 3/4 inch, and CertainTeed says 1/2 inch when there is a drip edge. Follow the sheet of the shingle you buy.

Step 4: the starter course

7. The starter goes along the eaves first, and along the rakes if your maker says so. GAF says to use starter strip shingles along the eaves and rakes.
8. Owens Corning says to trim 6-1/2 inches off the rake end of the first starter shingle, and to use 5 fasteners per starter shingle. CertainTeed says 4 nails for its starter. The starter has its own nail line, so use the maker’s diagram.

Step 5: field courses and offsets

9. Start with a full shingle nailed on the lower nail line, exposing 5-5/8 inches (GAF’s first course rule).
10. Offset each course so the joints do not line up. Owens Corning’s Duration sheet uses a 6-1/2 inch offset and accepts 4 to 8 inches. ARMA says no cutout or end joint should be less than 2 inches from a nail in the course below.
11. Snap chalk lines every few courses to keep the rows straight (common practice).
12. Work from the low edge up. Set up fall protection before you climb (common practice).

Step 6: nailing

13. Use at least 4 nails per strip shingle, the model code’s floor and ARMA’s minimum for most shingles. GAF’s standard pattern is 4 nails about 6-7/8 inches from the bottom, and CertainTeed says four nails for every full shingle.
14. Place nails below the sealant strip and where they will not show. ARMA says no nail head should be less than 1 inch from either end of the shingle.
15. Drive nails flush. ARMA says under-driven nails can be tapped down, and over-driven or crooked nails come out.

Step 7: ridge cap

16. Finish the field shingles up to the ridge from both sides, then cap the ridge. ARMA says to apply the field shingles first, and to overlap the ridge cap at least 2 inches on each side of the ridge.
17. GAF tells you to follow the ridge cap wrapper and to position the laps away from the prevailing wind. The nail count for ridge cap varies by product, so read the wrapper.

Shingling a lean-to with a low slope

A lean-to roof is one plane, so the steps above apply, with two extra checks: the double underlayment and the high edge.

3/12 and 2/12 fall under the double rule

The model code asks for double underlayment from 2:12 up to 4:12. The designer’s lean-to presets are 3/12, and its 2/12 setting sits at the model code’s floor. At either pitch the designer warns that the roof needs two layers, and it adds the second layer to its underlayment count.

CertainTeed goes further. Its Landmark Series manual says all shingles on a low slope of 2 inches to below 4 inches per foot need CertainTeed WinterGuard or VYCOR waterproofing underlayment, or an equivalent, over the entire deck. That is a maker asking for more than the model code’s felt. Where two sources differ, the wrapper and the maker’s low-slope sheet decide, and so does your building department.

Does one roll cover two layers?

The designer’s list counts 1 roll of 10 squares on every preset. On the four lean-tos the underlayment squares, with the second layer and laps, run from 0.9 on the 8x4 to 2.6 on the 12x8. Even at 2/12, the 12x8 comes to 2.5 squares. That is well inside a 10-square roll, so one roll covers two layers on these small roofs by the designer’s count. A roll smaller than 10 squares might not, so read the coverage on the label.

The high edge of a lean-to

The designer lists no ridge cap for a lean-to, because there is no ridge. The high edge meets a wall, a fascia or the house. Common practice is to run the shingles up to the top edge and cover the joint with a cap course or with metal flashing, following the shingle maker’s instructions for the way it meets a wall. Where the lean-to touches a house, the wall flashing details are a job for the shingle maker’s instructions and your building department.

Weather, sealing and when to wait

Shingles seal from the sun. GAF says its shingles have a thermal sealant that bonds after installation when exposed to sun and warm temperatures, and that if they are laid in prolonged cold, or if dust or sand gets on the sealant, they must be hand sealed. Owens Corning sets a number: below 40F, hand-seal every shingle on the perimeter with four 1 inch dabs of asphalt cement.

If you cannot roof in one dry, warm window, put the underlayment down and finish when the weather allows, and check how long the underlayment’s label lets it stay uncovered.

Where to go next

Open the designer on a 10x12 gable with shingles or a 10x8 lean-to and change the pitch or the overhang. The roof area, bundles, starter, ridge cap, underlayment and drip edge all update. The full cut list for the 10x8 lean-to plan lists the same roofing. The how to build a shed guide puts this step in the order of the whole build, and the shed siding guide covers the trim that meets the roof edge.