What You Need Before You Start
Roof shingle installation requires specific tools, materials, and safety equipment. Before you climb onto the roof, gather everything on the ground so you are not making trips up and down. You will need a hammer or pneumatic nailer, a utility knife, a tape measure, a chalk line, roofing nails (typically 1.25 inches for asphalt shingles), and the shingles themselves. Most asphalt shingles come in bundles of three, with each bundle covering roughly 33 square feet.
Safety equipment is not optional. Wear a harness rated for roof work, use a rope anchored to a find point, and wear shoes with good grip. If the roof pitch is steep (over 6:12), consider renting or buying roof brackets that attach to the roof edge. Work on a clear day — wet shingles are slippery and dangerous. Never work alone, and tell someone on the ground what you are doing.
Inspect the roof deck and underlayment before you start. If the wood is soft, rotted, or missing, the shingles will fail. Replace damaged decking first. If the underlayment (the waterproof layer under the shingles) is torn or missing, repair or replace it. These steps take time but prevent water damage later.
Key Takeaways
- Start at the bottom edge of the roof and work upward in horizontal rows, nailing each shingle with four nails placed in the manufacturer's nail line.
- Offset the shingles in each row so the seams do not line up vertically, which prevents water from running down the seams.
- Nail placement matters: too high and the nail misses the shingle above it; too low and you split the shingle or leave it loose.
- Roof flashing around chimneys, vents, and valleys requires different techniques than field shingles and is where most leaks start.
- Asphalt shingles typically last 15 to 25 years depending on climate, ventilation, and maintenance.
Starting at the Eaves and Working Upward
Begin at the lowest edge of the roof, called the eave. Snap a chalk line parallel to the eave, about 5 inches up from the edge. This line guides your first row of shingles and ensures they are straight. Lay down a starter strip — this is a row of shingles placed upside down, with the adhesive side facing up. The starter strip fills the gaps between the tabs of the first visible row and prevents wind from lifting the shingles.
Once the starter strip is in place, lay the first row of shingles right-side up, aligned with your chalk line. Drive four nails into each shingle, placing them in the nail line marked on the shingle itself. The nail line is usually about 5.5 inches from the bottom of the shingle. Drive the nails straight in — angled nails can tear the shingle or miss the deck. The nail head should sit flush with the shingle surface, not driven so hard that it crushes the material.
After the first row is complete, move up to the second row. This is where offset matters. The shingles in the second row should be staggered so that the seams do not line up with the row below. Most roofers start the second row with a half-shingle (cut a shingle in half lengthwise) so that the tabs are offset by half a tab width. This pattern continues up the roof and prevents water from running straight down the seams.
Nailing Pattern and Nail Placement
Nail placement is the most common mistake in shingle installation. Each asphalt shingle has a nail line printed on it — a thin line or series of dots showing where nails should go. Drive four nails per shingle, one in each nail slot above the tabs. If the shingle has five tabs, you still use four nails, not five. The nails should be placed so that the shingle above it will cover the nail head completely.
The depth of the nail matters. The nail should penetrate the roof deck by at least 0.75 inches. If you are nailing through two layers of shingles (when replacing shingles over existing ones), the nail must go through both layers and into the deck. A nail that sits on top of the lower shingle will not hold. Use a pneumatic nailer set to the correct pressure — too much pressure drives the nail too deep and splits the shingle; too little leaves it loose.
In high-wind areas, some roofers add a fifth nail at the top center of each shingle, or use roofing cement under the shingle tabs to seal them down. Check your local building code or the shingle manufacturer's instructions for your climate zone. Wind uplift is a real problem in coastal areas and on tall buildings, and the extra fastening is worth the time.
Handling Valleys, Flashing, and Edges
Valleys are the V-shaped channels where two roof planes meet. Water runs down valleys faster than anywhere else on the roof, so the shingles here must overlap correctly and be sealed. There are two common methods: the closed-cut valley (where shingles from one side overlap the other) and the open valley (where metal flashing is visible in the center). Follow the method specified in your roof plan or building code.
Flashing is metal or rubber material that seals the gaps around chimneys, vents, skylights, and roof edges. Flashing installation is different from field shingles. Typically, you nail the flashing first, then lay shingles over the top of it, then seal the overlap with roofing cement. The order matters: if you nail the shingles first, the flashing will not sit flat. Roofing cement is not waterproof by itself — it is a backup seal. The shingles and flashing must overlap so water runs down and out, not into the gap.
At the ridge (the peak of the roof), shingles meet at an angle. You can buy pre-made ridge caps or cut shingles into 9-by-12-inch pieces and fold them over the ridge. Ridge caps are nailed on both sides and sealed with roofing cement. This is the last step in shingle installation and is often the most visible part of the roof.
Common Mistakes and How to Avoid Them
Nailing too high is the most common error. If the nail is above the nail line, it will not be covered by the shingle above it, and water will run into the hole. If the nail is too low, it may split the shingle or miss the deck entirely. Use the printed nail line as your guide every time. If the line is hard to see, mark it with a pencil before you start nailing.
Skipping the starter strip or installing it upside down causes wind damage. The starter strip fills the gaps between tabs and prevents wind from getting under the shingles. If you skip it, the first row of visible shingles will lift in the wind. If you install it right-side up instead of upside down, the adhesive will not seal properly.
Laying shingles in a straight line without offset looks neat but fails quickly. Water finds the seams and runs down them. Offset the rows so that no two seams line up vertically. A half-shingle at the start of every other row is the standard method and takes only a few extra minutes per roof.
Ignoring flashing or sealing it with only roofing cement causes leaks around vents and chimneys. Flashing must overlap the shingles so water runs down and out. Roofing cement is a backup, not the primary seal. If the flashing is not installed correctly, no amount of cement will stop the leak.
Tools and Materials Checklist
| Item | Purpose | Notes |
|---|---|---|
| Roofing nails (1.25") | Fasten shingles to deck | Use galvanized or stainless steel to prevent rust |
| Hammer or pneumatic nailer | Drive nails | Pneumatic is faster; hammer gives more control |
| Utility knife | Cut shingles to size | Keep blades sharp; dull blades tear shingles |
| Chalk line | Mark straight rows | Essential for alignment |
| Tape measure | Measure distances and offsets | 25-foot minimum |
| Roofing cement | Seal flashing and ridge caps | Use sparingly; it is a backup seal, not primary |
| Roof harness and rope | Safety | Non-negotiable on any pitch over 4:12 |
Frequently Asked Questions
Can I install new shingles over old ones?
Yes, but only if the old shingles are in reasonably good condition and the roof has only one existing layer. Building codes in most places allow two layers maximum. Installing over old shingles saves time but makes nailing harder because the nail must go through two layers. Use longer nails (1.5 inches) and check that they penetrate the deck. If the old shingles are curled, missing, or the roof is already two layers deep, remove the old shingles first.
What temperature should it be when I install shingles?
Asphalt shingles are stiff in cold weather and may crack if you bend them. Most manufacturers recommend installing when the temperature is above 50 degrees Fahrenheit. In cold weather, store the shingles indoors or in the sun before installation so they warm up and become flexible. In very hot weather (above 85 degrees), the adhesive on the shingles may set up too quickly, making them stick to your hands and tools.
How do I know if a nail is driven deep enough?
The nail head should sit flush with the shingle surface — you should not be able to catch your fingernail under it. If the nail is proud (sticking up), tap it in further. If you drive it too deep and crush the shingle, pull it out and move it slightly to the side. A nail that is too shallow will not hold in wind, and a nail that is too deep splits the shingle.
What should I do if I run out of shingles partway through?
Stop at a natural break point — the end of a row — and cover the exposed area with plywood and a tarp until you can get more shingles. Do not leave the roof deck exposed to rain overnight. Shingle colors can vary slightly between batches, so try to buy all shingles from the same production run if possible. If you must use shingles from different batches, blend them by mixing shingles from each batch as you lay them.
Do I need to remove old flashing when I install new shingles?
If the old flashing is in good condition and sits flat, you can leave it and shingle over it. If it is rusted, bent, or leaking, remove it and install new flashing before you lay the shingles. Removing old flashing is easier than trying to work around it, and new flashing is inexpensive compared to the cost of a leak.