If stucco were applied to the edge of an aluminum window, a crack would appear after the stucco cures and shrinks, and every time the window moves due to expansion and contraction. For example, aluminum windows and Portland cement have vastly different coefficients of expansion, and therefore expand and contract quite differently. This product (shown in Image 2) serves to protect the edge of the stucco, and also provides stress relief at windows, doors and other openings where dissimilar material might come into contact with the stucco membrane. It consists of an expanded back flange, a ground leg that matches the stucco thickness, and a 1/4-inch return lip that helps to avoid water intrusion. As the name would imply, this product is used to terminate stucco at all openings and at the top of all walls. The accessory that is generally installed next is the casing bead or plaster stop. Image 1 shows the proper application of this bead. This shrinkage results in a minor crack at the junction of the angular ground and the stucco membrane, allowing moisture to escape. All Portland cement stucco shrinks slightly when hydration and curing occurs. Should moisture make its way to the water resistant building paper, it will flow down the surface of the paper to the foundation weep screed, follow the contour of the angular surface of the ground or screed edge, and exit the cementitious membrane. While the stucco membrane is quite water resistant, it is possible over time for structural cracks or separations of the stucco at accessory edges to occur. Attachment mechanisms must be spaced no more than 7 inches on center. The attachment flange is 3 1⁄2 inches long and also serves as a flashing mechanism when the building paper is installed to cover this flange. It is a good idea to install an 8- to 10-inch strip of reinforced asphalt saturated paper flashing over the sheathing behind this screed. If sheathed, the attachments must pass through the sheathing and into the framing members. This accessory is installed 2 to 6 inches above the ground (depending on whether it is paved or grade) and attached to the wooden foundation plate, or the bottom of the framing or studs in light-gauge steel frame construction. Installed at the bottom of all framed walls, it serves as one of the most important components of a redundant drainage system. The first accessory to be installed is generally the foundation weep screed.
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