starter strip

A starter strip is a course of roofing material laid along the eave edge before the first visible course of shingles or roll roofing goes down. It sits upside-down or reversed, with its adhesive or nailing side facing up, creating a solid base that bridges gaps left by the cutouts and staggered joints in the first course above it. This is not decorative; it closes the gap between shingles and prevents wind-driven rain and debris from entering the rafter space.

Starter strips come in several forms. For asphalt shingle roofs, contractors typically use a roll of starter shingle material, cut from standard three-tab or architectural shingle stock, or a factory-made starter roll with adhesive pre-applied. For roll roofing applications, the starter is simply the first width of material, mineral-side down. The strip must extend the full width of the roof run and typically measures 6 to 8 inches wide, though some installers use a full-width shingle (10 to 12 inches) for extra protection.

Proper fastening matters greatly. Starter strips need more nails than regular courses because they bear the weight and stress of water being driven upslope under the first course during heavy wind-driven rain. A single fastener every 12 inches is minimum; many roofers use 6-inch spacing along the eave and 12 inches across the width. Nails should be spaced one inch up from the eave edge to avoid splitting the material. If the nailing is too light or too high, the starter strip can lift and curl, compromising the entire roof's water seal.

Where it fails

Installation errors at the starter strip stage create the majority of eave-level leaks. The most common mistake is laying the starter course in the same orientation as the first shingle course, which defeats its purpose. Another is using regular shingles as a starter when conditions require roll roofing, or vice versa, creating an incompatible bond. On metal roofing, the equivalent function is performed by a closure strip or trim piece, not a full strip, since metal seams are sealed differently.

The starter strip is often invisible in the finished roof, which is exactly why many new roofers underestimate its importance. It is the first thing to wear on an old roof because it sits in the eave drip zone where water concentrates and UV exposure is most intense. When you see granule loss concentrated along the lower edge of a roof, the starter has usually failed first, followed shortly by the first course.