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Making EIFS Watertight - Continued The solution in this case — as in so many others like it — was to tear off the improperly applied EIFS, repair the underlying water damage and rot, and reapply the EIFS system, this time leaving the required caulk spaces (Figure 4).

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Figure 4. In a correctly executed butt joint — like the one in progress here — the edge of the insulation board is held back 1/2 to 3/4 inch, then backwrapped with mesh and base-coated. Note the backer rod and the well-tooled bead of caulk.

Flashing Details

Any joints between an EIFS wall and a flashed header should also include a suitable caulk space. I prefer soldered copper pan flashing in this application, because it's reliably leakproof and will last at least as long as the wall itself (Figure 5).

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Figure 5. Headers and other horizontal surfaces must be protected with flashing. In this case, the damaged EIFS system has been stripped off, and a waterproof fiberglass-faced gypsum board screwed to the studs. The EPS board is attached to the sheathing with adhesive. Once the reinforcing mesh has been turned up at the front, the bottom edge of the sheet will receive a layer of basecoat.

Better step flashing. Another common trouble spot is the joint where a wall meets step flashing at the edge of the roof. More often than not, the EIFS-covered beadboard is simply butted and caulked against the shingles (Figure 6).

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Figure 6. Contrary to the manufacturer's recommendation and common sense, the EIFS applicator butted the edge of the polystyrene directly against the roofing, with no caulk space or counterflashing.

Once this makeshift seal fails — as it soon does — the stage is again set for disaster as water wicks into the polystyrene, over the vertical leg of the flashing, and into the interior of the wall.