How to Install 3-Tab Shingles: Layout, Tab Alignment and the 6 Inch Offset
Flat, single-layer shingles with visible slots. Every misaligned tab shows, so the layout has to be right.
- Advanced
- 1 to 2 days for an average roof
- Updated
The short answer
A 3-tab shingle is a flat strip of about 12 by 36 inches with three tabs separated by slots and an exposure of 5 inches. Start with a full shingle over a cut-down starter, then offset each course 6 inches so slots never line up for at least five courses, keeping tabs aligned to chalk lines. Nail 4 per shingle just above the slots, and confirm details on the wrapper.
The 3-tab shingle is the traditional asphalt shingle: a flat, single-layer strip, usually 12 inches by 36 inches, with two slots cut into the bottom that divide it into three tabs. It has an exposure of 5 inches and a flat, uniform look. It is lighter and thinner than a laminated shingle, which is why it was the standard for decades and why so many older roofs in the Fraser Valley are covered in it.
Because it is flat and thin, every misalignment shows. A tab that is a quarter inch out of line, or slots that line up two courses in a row, catches the eye. That is why the layout pattern matters more on 3-tab than on laminated shingles. A laminated shingle hides small errors in its shadow lines and texture. A 3-tab shows them.
This guide covers layout, offsets and nailing for 3-tab shingles. The general method is in how to lay shingle courses and offsets. Many manufacturers have reduced or discontinued their 3-tab lines, so on a repair you may need a close match or an alternative, and a full replacement is often the better long-term answer.
Tools
- Roofing coil nailer and compressor
- Hook blade utility knife
- Chalk line
- Tape measure
- Shingle gauge
- Framing square
- Fall arrest harness and anchor
Materials
- 3-tab asphalt shingles
- Starter strip or cut 3-tab shingles
- Roofing nails, 1-1/4 inch galvanized
- Underlayment and drip edge
- Hip and ridge cap
- Asphalt roof cement
Safety first
- Stay tied off and keep your footing on the slope, since 3-tab shingles are thin and can curl at the edges in heat.
- Hook blades cut toward you. Keep the blade and your free hand away from your legs.
- Old 3-tab roofs are brittle. Test the deck and avoid walking on cracked or curled shingles.
Step by Step
Step 1: Prepare the eave and install starter
Starter goes on first. A manufactured starter strip is best. If you must make starter from 3-tab shingles, cut off the tabs so a strip of about 7 inches remains, with the sealant line near the cut edge, and lay it with the cut edge at the eave overhang. See how to install starter strip shingles.
The starter must overhang the drip edge by about 1/4 to 3/4 inch, and its joints should not line up with the joints of the first course.
Step 2: Snap layout lines for exposure and tabs
With 5 inches of exposure, four courses measure 20 inches and six courses measure 30 inches. Snap a horizontal line every few courses. The lower edge of every tab should sit on its line. See how to snap chalk lines for shingle courses.
For the 6 inch pattern, snap vertical lines at 6 inch intervals from the starting rake, or one line for each diagonal. The slots in the course above should fall at the marks.
Step 3: Lay the first course
The bottom edge of the first course sits on the starter overhang. Butt each shingle to the last so the tabs have a consistent gap at the slots. Gaps or overlaps at the butt joints show as dark lines or bumps.
Nail each shingle as laid, with 4 nails in the nailing zone. See shingle nailing: placement, count and depth.
Step 4: Apply the 6 inch offset pattern
With 12 inch tabs, a 6 inch offset puts each slot halfway across the tab below. Course 2 starts with a shingle cut 6 inches shorter, course 3 with one cut 12 inches shorter, and so on to 30 inches for course 6, after which the pattern repeats with a full shingle. The diagonal of slots steps up the roof at a steady angle.
Some manufacturers allow a 4 inch offset or a random pattern, but slots should not line up within two courses and butt joints should not align. Check the wrapper. The pieces you cut off the start of each course are used to finish the rake end of another course.
Tip: Keep the cut-off pieces in order. Piece for course 2 goes to the far end of course 6, and so on, which wastes nothing.
Step 5: Keep the tabs aligned to the lines
The bottom of each tab should be straight on the line. A tab that is pushed up or down creates a wave in the course. If you see drift, correct it over two or three courses, not in one step.
Check that the slots in each course are aligned with the marks. The pattern shows its errors after a few courses, so check early.
Step 6: Trim at the rake, valleys and hips
Trim at the rake after the course is nailed, along a chalk line, and see how to finish shingles at the rake edge. At a hip, cut to the hip line and see how to shingle a hip roof.
With 3-tab shingles, a thin piece of tab at a valley or rake is easy to lift. If a cut would leave a narrow sliver, adjust the start of the course so a wider piece falls at the edge.
Step 7: Cap the hips and ridge
Many 3-tab roofs were capped with shingles cut along the slots, each piece bent over the ridge. Current instructions often require a manufactured cap, which is thicker and less likely to crack. See how to install hip and ridge cap shingles.
Use the same exposure as the field, and start from the end away from the wind.
Repairing an Older 3-Tab Roof
Old 3-tab roofs are brittle, and the sealant has long since failed. To replace a single damaged tab or shingle, lift the course above with a flat bar, remove the nails and slide the new shingle under, then nail and seal it. See how to replace a damaged shingle. Warm weather helps, since cold 3-tab cracks when lifted.
Matching is the other problem. Many 3-tab colours have been discontinued, and a new shingle will not match an old one in colour or thickness. A roof with widespread curling, cracking, granule loss or moss growth is near the end of its life, and repairs may not be worth it. See how to tie new shingles into an existing roof and roof replacement.
3-Tab Versus Laminated
A 3-tab shingle is one layer, thinner and lighter, with a flat look. A laminated shingle is two laminated layers, heavier, with a dimensional look and usually a longer warranty and higher wind rating. Laminated shingles are more forgiving of small layout errors. For a new roof, most installers use laminated shingles, and 3-tab is chosen mainly for low cost or matching an existing roof.
Common Mistakes
- Lining up the slots. Slots in two adjacent courses in the same place let water through and look bad.
- Offsets of less than the manufacturer's minimum. Water finds the joint and the pattern looks uneven.
- Tabs out of line. A flat shingle shows every wave in the course.
- Nailing in the slots or too high. Nails in a slot are exposed, and nails too high miss the headlap.
- Using 3-tab for ridge cap where not allowed. Cut caps crack in cold weather. Use manufactured cap.
- Repairing a roof that is past its life. Brittle shingles crack as you lift them, and new tabs will not match.
When to Call a Professional
A simple 3-tab roof is a fair job for a capable DIYer with help, but alignment mistakes are permanent and visible. If the roof has hips, valleys and dormers, is steep, or the old roof is brittle and failing, have a roofer do it.
If you are thinking of repairing an old 3-tab roof, have a roofer judge its remaining life first. A repair that costs as much as a fraction of a new roof may not be the best money.
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 Install 3-Tab Shingles: Questions
What is the exposure of a 3-tab shingle?
Most 3-tab shingles are about 12 by 36 inches with an exposure of 5 inches. That is the part of the shingle that shows below the course above. Four courses measure 20 inches, and there are about 80 shingles in a square. The wrapper states the exact dimensions and exposure for the product.
What is the 6 inch offset for 3-tab shingles?
It is a layout where each course starts with a shingle cut 6 inches shorter than the one below, so slots shift by half a tab each course. The slots then step diagonally across the roof. After 6 courses the offset reaches 30 inches, and the pattern repeats with a full shingle.
How many nails per 3-tab shingle?
Four nails per shingle in a standard installation, placed in a line about 5/8 inch above the top of the slots, one about an inch in from each end and two spaced between. Steep roofs and high-wind areas call for six nails, per the manufacturer. Nails driven too high or into the slots reduce holding power.
Are 3-tab shingles still made?
Some manufacturers still make them, but many have reduced or discontinued their lines in favour of laminated shingles. Availability and colours vary by region and supplier. If you are repairing an older roof, a perfect match may not be available, and a close match or a full replacement may be needed.
Can you repair a 3-tab roof with new shingles?
Yes, if the roof is still sound. Lift the course above, slide the new shingle under, nail it and seal the tabs with roof cement. Warm weather helps because old shingles crack in the cold. A roof with widespread curling or granule loss is near the end of its life, and patching may not be worth it.
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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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