How to Lay Shingle Courses and Offsets Across the Field of a Roof
Start square, hold the exposure, offset every joint and keep the line. The rhythm of the field of the roof.
- Advanced
- 1 to 2 days for an average roof
- Updated
The short answer
Lay the first full course over the starter, flush with the rake, then build each course up the roof at the printed exposure (about 5-5/8 inches for laminated shingles), offsetting joints at least 4 to 6 inches from the course below so no joint lines up within two courses. Blend bundles, keep to the chalk lines, nail in the zone, and trim at the rake after the course is down.
The field of a roof is the big, open area between the edges, valleys and penetrations, and it is where most of the shingles go. Laying it well is repetition: the same nail pattern, the same exposure, the same offset, hundreds of times. A crew that has the rhythm can do a couple of squares an hour on a simple roof. A crew that does not ends up with crooked courses, joints that stack up and bubbles that show in the evening light.
Three things define a good field: exposure, the amount of each shingle left showing; offset, how far each joint is shifted from the joints above and below; and alignment, how straight the courses run. All three come from the layout work that precedes the first shingle. Good chalk lines and proper starter are what make the field easy.
This guide covers laminated (architectural) shingles in the open field. For the older tab pattern, see how to install 3-tab shingles. Fasteners are covered in shingle nailing: placement, count and depth.
Tools
- Roofing coil nailer and compressor
- Hook blade utility knife
- Chalk line
- Shingle gauge
- Tape measure
- Roof jacks on steeper pitches
- Fall arrest harness and anchor
Materials
- Laminated asphalt shingles
- Roofing nails, 1-1/4 inch galvanized
- Asphalt roof cement for hand sealing
- Underlayment, starter and drip edge already installed
Safety first
- Shingles on a slope slide. Keep bundles blocked and keep your body uphill of the edge you are working toward.
- Heat, footwear and granules all affect grip. Wear soft-soled boots and never work barefoot or in worn soles.
- Stay tied off. Most falls during shingling happen at the first and last courses, when the edge is close.
Step by Step
Step 1: Lay the first full course over the starter
The first course sits on the starter strip with the same eave overhang, so the starter sealant bonds it. Start with a full shingle at the rake end, with its outer edge flush with the rake starter or overhanging by the amount the manufacturer specifies, then continue across, butting each shingle tight to the last.
Nail each shingle as you lay it, following the nailing pattern. Pull the shingle flat before nailing so there is no bow or buckle.
Step 2: Set the offset for the second course
Offsets keep water from finding a straight path between joints. Most laminated shingle instructions call for a minimum offset of around 4 to 6 inches between joints in adjacent courses, and some also require that joints not line up for two courses. Check the wrapper.
Cut the first shingle of each new course to the length that gives the offset. The cut-off piece is the start of the next course, so nothing is wasted. See how to cut asphalt shingles cleanly.
Step 3: Choose stair-step or racking
Stair-step means laying each course one shingle shorter than the last, so the work climbs the slope on a diagonal. It blends shingles across the roof and is the usual recommendation, because shade differences between bundles are spread out. Racking means laying a vertical column of shingles up the roof before starting the next column. It is fast and keeps the crew in one spot, but it is more likely to show shading lines.
Some manufacturers discourage or forbid racking, especially on large, dark or contrasting roofs. The wrapper says whether it is allowed. If you do rack, keep the column narrow, and blend bundles.
Step 4: Blend bundles as you go
Even in the same lot, bundles vary in shade. Laid one bundle at a time, the differences show as patches. Open three or four bundles together and alternate, and never finish a whole slope from one batch.
Keep bundles stored flat and square so they do not warp. Wrinkled shingles pull a course crooked.
Step 5: Hold the exposure with the chalk line
Lay each course by measuring up with a shingle gauge, and check against the chalk lines every few courses. If a course is off by an eighth of an inch, correct it over the next two courses, not in one step.
Keep the bottom edge of each course straight, and keep the tabs or lower layer aligned with the line, not the shingle ends. A course that bows up in the middle shows on the whole slope.
Step 6: Nail as you lay, keep the shingle flat
Hold the shingle so the lower edge lines up with the exposure and the top edge fits against the course above. Nail from the centre toward the ends, so any slack is pushed out, not trapped in the middle.
Check that nails are flush. A proud nail makes a bump that shows in the next course, and an overdriven nail holds nothing. See shingle nailing: placement, count and depth.
Step 7: Trim at the rake and butt to cut lines
At the rake, trim each course so the shingle overhangs the rake by about 1/4 to 3/4 inch along a straight line. Many roofers nail the course, then snap a line and cut with a hook blade. See how to finish shingles at the rake edge.
At valleys, hips, walls and dormers, cut the shingles to the line and leave the gap the detail requires. See how to shingle a hip roof and how to shingle around a dormer.
Step 8: Finish at the ridge
The last course below the ridge is often cut to fit. Trim it so its top edge is at or just below the ridge, and set the nails below the ridge line so the cap covers them. Do not leave a gap at the ridge, because the cap must sit on shingle, not on bare deck.
Shingles at the ridge from each slope should butt together at the peak, with the cap covering both. See how to install hip and ridge cap shingles.
Why Offsets Matter
Every joint between two shingles is a place water can find the deck. The shingle in the course above bridges the joint, so the water runs over it instead. If the joints line up, or are only an inch or two apart, water running down the roof finds a straight path through two courses, and the bridging layer is too thin to help. Wind also finds an aligned joint and gets under the edges.
A good offset also looks better. A roof with staggered joints shows an even pattern, and one with stacked joints shows lines that run up the slope.
Fraser Valley Notes
Shingle granules and sealant strips need warmth to bond. In the long damp season between October and March, plan on hand sealing more often, and lay shingles in a dry window whenever one is forecast. Moss grows fastest on shaded north slopes, so shingles there are worth installing with particular care. See how to shingle in cold weather.
Common Mistakes
- Stacked joints. Joints within an inch or two of the course below let water straight through two layers.
- Racking with mixed bundles. Shade variation shows as vertical stripes.
- Drifting off the chalk line. Courses creep crooked and end badly at the ridge.
- Shingles jammed together. Buckled or overlapping joints cause bumps, and shingles need room to expand.
- Nailing with the shingle bowed. Slack trapped in the course pushes the tab up and breaks the seal.
- Leaving the last course to chance. Cutting the ridge course late leaves a gap, a short course or exposed nails.
When to Call a Professional
A plain roof with a good layout is a fair job for a capable homeowner with help, but every part of the field needs care. If the roof is steep, cut up with hips, valleys and dormers, or you have not laid shingles before, a roofer will be quicker and will get the details right.
The field also shows every mistake, and every mistake is permanent. A short trial on a shed or garage is a good way to learn the rhythm before you start on the house.
Fraser Roofing does free roof inspections across the Fraser Valley, from Hope to Abbotsford. See our Roof Replacement service or the towns we cover.
How to Lay Shingle Courses and Offsets: Questions
How far should shingle joints be offset?
Most manufacturers ask for at least 4 to 6 inches between joints in adjacent courses, and some also require that a joint not line up with the joint two courses above or below. The exact figure is on the wrapper. The offset stops water running straight through and gives the roof an even pattern.
What is the exposure of architectural shingles?
Most laminated architectural shingles have about 5-5/8 inches of exposure. That is the part of each shingle left visible below the course above. The figure is printed on the wrapper. Changing the exposure changes how much of each shingle is covered, so keep to the manufacturer's figure and adjust only by small amounts across many courses.
What is racking shingles?
Racking is laying shingles in a vertical column up the roof, instead of working across in courses. It is fast and needs fewer trips across the roof, but it can produce visible shading lines and is prohibited by some manufacturers. A stair-step diagonal pattern blends shade better and is the more common recommendation.
Which way do you lay shingles, left to right?
Either direction works, as long as the layout and offsets are consistent. Many roofers start at the end that gives the best walking and working position, and lay towards the far rake. The important part is starting from a square, true line and keeping to the offsets and exposure on the wrapper.
How do you keep shingle rows straight?
Snap a chalk line for the first course and every few courses above it, and use a gauge to set each course between lines. Check the lines against the ridge early, and correct small errors gradually over a few courses. A crooked eave should be corrected in the first few courses, not followed up the roof.
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This guide is general education. Always follow the product manufacturer's installation instructions, the BC Building Code and WorkSafeBC requirements, which take priority over anything written here.
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