What type of flashing should always be used at sidewalls with asphalt shingles?

Step flashing is the correct selection for use at sidewalls with asphalt shingles because it provides a robust way to divert water away from the intersection of the shingles and the wall. Step flashing consists of individual sections of flashing that are installed in a manner that allows them to work effectively with the shingles.

The design involves placing each piece of flashing under the shingles at the top, while the end of each piece extends up the wall. This arrangement forces water that runs down the roof to hit the flashing and flow out and away from the wall, thereby minimizing the risk of water penetrating behind the shingles. This method is particularly important at sidewalls because they are common points where water can infiltrate a roofing system.

Continuous flashing, while it can be used in some roof-to-wall applications, does not work as effectively as step flashing in managing the dynamic flow of water at each shingle course, especially where varying elevations or profiles of shingles occur. Counter flashing is typically used to prevent water infiltration at masonry walls or chimneys and doesn’t provide the same incremental protection that step flashing does at the sidewall.

Using step flashing appropriately at sidewalls contributes to the longevity of the roof covering by reducing the likelihood of leaks, which is crucial in maintaining the integrity and performance