Can step flashing go over shingles?

Step flashing should not go over shingles in the sense of being placed entirely on top of finished shingles, as proper step flashing installation requires it to be interwoven with shingle courses to create a watertight layered system. Each L-shaped piece of step flashing is designed to go under one shingle course and over the shingle course below, creating a stair-step pattern along sidewalls and chimneys. If step flashing is placed entirely over shingles, water running down the wall will run behind the flashing and under shingles, causing leaks. The correct method is that the lower part of the flashing sits on top of the shingle below, while the next shingle above covers the flashing, so water flows from wall onto flashing onto shingle. The only exception is the bottom piece of step flashing at the eave, which may go over the starter course, and counter flashing which goes over step flashing. When repairing, you cannot simply lay step flashing over existing shingles and caulk it, as this relies on caulk that will fail. You must remove surrounding shingles, install step flashing properly integrated, and reinstall shingles. Some homeowners mistakenly install continuous L-shaped flashing over shingles instead of individual step pieces, which is improper and prone to leaks because it does not accommodate movement. Always follow manufacturer instructions for proper step flashing integration.