Roofing Glossary

Step Flashing

Step flashing is the series of small L-shaped metal pieces installed where a sloped roof meets a vertical wall — along dormer sidewalls, for example. Each piece is woven into the shingle courses: one step flashing per shingle course, overlapping like scales.

The stepped, overlapping design means water running down the wall or the roof is always directed outward over the shingle below — never behind it. It is simple physics, and when installed correctly it is essentially permanent.

Step flashing fails when it is omitted (a shockingly common shortcut where caulk or sealant was used instead), when it corrodes, or when a re-roof crew shingles over old flashing instead of weaving in new pieces.

Why It Matters

Sidewall leaks are almost always step flashing problems. If you see water stains where a dormer or addition wall meets the roof, step flashing is the first suspect — and the fix requires removing shingles to install it properly, not caulk.

What to Watch For

• Stains on walls below a roof-to-wall joint
• Caulk smeared along a sidewall instead of visible metal steps
• Flashing pieces pulling away from the wall

Questions about your own roof? Request a free estimate or call Nucci Brothers Roofing at (301) 458-1003.