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Stucco Flashing Details -

Continued Equally important is a kick-out flashing at the edge of the eaves. This metal flashing is really the first line of defense, because it catches any water coming off the roof and directs it away from the wall surface (for kick-out detail, see "Installing Water-Managed Synthetic Stucco," JLC 9/98). As with all other flashing details, the building paper should be layered properly so that water drains to the bottom of the wall.

Horizontal Surfaces

Horizontal stucco surfaces, such as balcony railings and pot shelves at recessed windows, are especially prone to leaks because they are fully exposed to the weather. Unless they are carefully detailed, water from repeated soakings or ponding will eventually penetrate the stucco base and finish coats and wet the underlying framing. When the wood swells from this extra moisture, it causes the stucco to crack, which leads to more leaks, more swelling, and more cracks. We always inspect the framing before flashing a horizontal surface to make sure that it slopes 1/4 inch per foot -- more, if possible -- so that water will drain freely. If the framing is level or, worse, sloped back toward the building, we won't touch it till the problem has been corrected.

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Figure 6. Leaks at parapets, pot shelves, and other horizontal surfaces can cause framing lumber to swell and crack the stucco. To promote drainage, the horizontal framing must be adequately sloped and should be fully flashed with a self-adhering membrane. The stepped slab also serves to contain leaks.

On a properly sloped horizontal surface, we apply a layer of Vycor adhered directly to the sheathing and extending down over the edges to overlap any building paper coming up the sides (Figure 6). If the surface is in front of a window, we run the membrane under the bottom nailing flange and onto the sill plate. Similarly, where the horizontal surface meets a wall, we run the membrane up the wall where it will be overlapped by building paper. As with all of our flashing, we're careful not to tear or punch holes in the paper, and we make sure that the paper is layered so that water will drain away from the building. Use as few nails as possible on the horizontal surface, and caulk or patch every rip, tear, or hole.

Ron Webber

owns and operates Prime Plastering in Norco, Calif. He has worked as a plasterer for more than 30 years.