Tools & Materials
Tools: a roofing nail gun or hammer, a utility knife with hook blades (for cutting shingles cleanly), a chalk line and tape measure for laying out exposure, a flat bar or shingle ripper for tear-off, roof jacks or a fall-protection harness, a magnetic nail sweeper, and tin snips for cutting flashing.
Materials (size the roof and count bundles with the Roofing Calculator):
- Asphalt shingles (3-tab or architectural), roughly 3 bundles per square — size with the Roofing Calculator
- Synthetic underlayment or roofing felt
- Ice-and-water shield membrane for eaves and valleys
- Metal drip edge for eaves and rakes
- Starter strip shingles and ridge cap shingles
- Roofing nails, plus step and valley flashing
- If you're re-siding the fascia or soffit or just repainting trim while the roof is torn off, size the paint with the Paint Calculator
Step 1: Tear Off and Inspect the Deck
Strip the old shingles, felt, and any exposed nails down to bare sheathing with a flat bar or shingle ripper, working from the ridge down so you're not standing on loose material. Once the deck is bare, walk every section and replace any plywood or OSB that's soft, delaminated, or water-stained. Shingles installed over a bad deck fail early no matter how carefully the rest of the job is done, so this is not the step to rush.
Step 2: Install Drip Edge and Underlayment
Nail metal drip edge along the eaves first, directly to the deck. Over it, run ice-and-water shield membrane at the eaves (typically at least 24 inches past the interior wall line, per local code) and in every valley, since those are the spots where ice dams and wind-driven rain most often find a way in. Cover the rest of the deck with synthetic underlayment or felt, overlapping each course, then nail drip edge along the rakes over the top of the underlayment.
Step 3: Set the Starter Course
Run starter strip shingles along the eave with the adhesive strip facing up, either factory starter strip or full shingles with the tabs trimmed off. The starter seals the first course against wind uplift and backs up the cutouts of the first row of field shingles — skip it and that first course has nothing sealing its seams.
Step 4: Lay the Field Shingles to the Exposure
Snap horizontal chalk lines up the roof to hold a consistent exposure — about 5-5/8 inches for standard strip shingles — and work course by course from one edge across. Drive nails in the nail line printed on the shingle: 4 nails per shingle for a standard install, 6 nails in high-wind zones or on steep pitches. Nails set above the nail line miss the course below and can work loose; nails set below it are often left exposed by the next course. Either mistake is a leak waiting to happen.
Step 5: Flash Valleys and Penetrations
In valleys, either weave the shingles across or cut them over valley flashing so the joint sheds water downhill instead of catching an open edge. At walls and chimneys, install step flashing one L-shaped piece per course, woven in as you shingle rather than added afterward. Around every plumbing vent or roof penetration, set a boot flashing before the surrounding shingles go on, and lap each course over the flashing's uphill side so water is always shed onto the layer below it, never against a seam.
Step 6: Cut and Install the Ridge Cap
Cut individual ridge cap shingles from factory ridge cap bundles (or cut them from full shingles along the tab lines) and bend each one over the peak. Start opposite the prevailing wind and work toward it, overlapping each cap so it covers the exposed nail heads of the one before it. If the ridge has a vent, cut the slot and cap directly over it last so the cap both finishes the roof and shields the vent.
Step 7: Final Flashing, Cleanup & Magnet Sweep
Seal any exposed nail heads, flashing laps, and boot collars with roofing cement, and double-check that every penetration is fully covered. Clear the gutters of tear-off debris, then run a magnetic nail sweeper across the yard, driveway, and any landscaping — do it more than once over the following days, since nails work their way out of debris and off tarps for a while after the crew leaves.
Common Mistakes
- High nails. Nailing above the nail line means the fastener only catches one layer of shingle instead of two, so it holds less and the exposed head under the next course can eventually leak.
- Wrong exposure. Drifting off the 5-5/8 inch reveal throws the courses out of alignment with the cutouts above them, and the error compounds all the way to the ridge.
- No starter strip or drip edge. Both exist to seal and protect the most vulnerable edge of the roof; skipping either invites wind-driven rain under the first course.
- Skipping ice-and-water shield. Eaves and valleys are where ice dams and wind-driven rain do the most damage — it's not a spot to save a few dollars.
Cost: DIY vs. Contractor
DIY materials for a typical 20–30 square roof (2,000–3,000 sq ft of roof surface, common for an average single-story house) commonly run $2,600–4,500 for shingles, underlayment, ice-and-water shield, drip edge, starter, ridge cap, and nails, before tool rental. Material prices vary by region and shingle type, so see how we source those numbers on our pricing methodology page and size your own roof with the Roofing Calculator before you order.
Contractor-installed re-roofs typically run $8,000–18,000 for that same size roof, more with a steep pitch, multiple layers of tear-off, extensive deck repair, or complex valleys and dormers. Given the fall risk and the warranty implications, most homeowners hire this one out — a shingle roof is one of the jobs where the labor, not the material, is what you're really paying for.
Related Calculators
- Roofing Calculator — Convert roof dimensions into squares and bundles
- Paint Calculator — Size paint for fascia, soffit, and trim while the roof is off
- Pricing Methodology — How we build the cost estimates behind our calculators
Written by Daniel McCarney — AceCalc