What type of flashing must be installed for most tile roofs against a wall?

The correct type of flashing that must be installed for most tile roofs against a wall is counter flashing. This is because counter flashing is specifically designed to work with vertical surfaces, such as walls, to create a watertight seal. It is typically installed over the step flashing, which is used to channel water down the roof and keep it away from the wall.

Counter flashing is essential in preventing water from infiltrating behind the tiles at the junction where the roof meets the wall. It acts as an additional barrier, effectively directing water over the step flashing and ensuring it drains properly rather than seeping into the wall or under the roof tiles. This is critical for maintaining the integrity of both the roof and the wall, preventing potential leaks and water damage.

While step flashing is also important in roof installations, it is primarily used along the edges of the roof rather than specifically against a wall, making counter flashing the appropriate choice in this scenario.