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Making EIFS Watertight - Continued Doing it right involves terminating the EIFS 2 inches above the roof, and including a run of counterflashing to provide a space for caulk and backer rod (Figure 7). When it's time to replace the original shingles, the roofer can slip the new shingles and step flashing beneath the counterflashing without damaging it.

Incorrect Roof-To-Wall Installation

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Correct Roof-To-Wall Installation

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Figure 7. Where EIFS butts directly against the roof (top), water will wick up into the foam board and eventually make its way past the flashing into the framing. The correct approach is to use a shaped counterflashing above the step flashing (above). The additional vertical leg creates a ledge for caulk and backer rod, and it keeps the polystyrene board clear of water running along the roof.

Two-piece head flashing. In the case of head flashing — at the eaves wall of a dormer, for example — it's often impossible to replace the top course of shingles without bending the flashing up out of the way. When it's bent back into place afterwards, the result can look pretty rough. Worse, bending and rebending the flashing can damage the caulk joint between the counterflashing and the EIFS, letting water seep through.

Head Flashing

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Figure 8. This two-piece head flashing provides a caulk space and makes it possible to renew the roofing without mangling the flashing. The counterflashing is secured to the base flashing with self-tapping sheet metal screws.

A two-piece flashing like the one in Figure 8 allows the roofer to remove and reinstall the base flashing without affecting the counterflashing. Harrison McCampbell, AIA, is a veteran EIFS troubleshooter in Nashville, Tenn.