How do you replace a single architectural shingle?

Why it takes two courses

Each shingle is held by its own nails and by the nails of the shingle above, which pass through its top edge. To pull a single architectural shingle you have to lift and unnail part of the course above it too. That is where most DIY repairs go wrong: the shingles above the repair get torn.

Steps

1. Pick a mild, dry day. Cold shingles crack; very hot ones tear and smear.
2. Slide a flat bar under the shingle above the damaged one and gently break the sealant strip along its length.
3. Pry out the nails in the damaged shingle, then the nails from the course above that pass through it.
4. Slide the old shingle out and the new one in, lining its edges up with its neighbors and the exposure line.
5. Nail the new shingle in the nailing zone with the count the manufacturer specifies, usually four, and re-nail the course above in fresh spots beside the old holes.
6. Seal the lifted shingles down with dabs of asphalt roofing cement, and seal the old nail holes.

Finding a matching shingle

Architectural shingles change size and shadow line between product generations, so check the garage or attic for leftovers first. A close color in the same profile will still look newer for a while. Moving a shingle from a hidden spot to the visible one, and putting the new shingle where nobody will see it, is an old roofer's trick.

When not to try it

Skip the DIY repair if the roof is steep, the shingles are brittle, or the damage came from a storm you might claim; photograph it first. See wind damage to roofs in Georgia and architectural vs 3-tab shingles.