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Paris Santa Fe-Frisco Depot Rehabilitation © KEYSTONE ARCHITECTS <br /> July 10, 2001 <br /> <br /> 1. Where existing mortar has been removed to a depth of greater than 1 inch, <br /> these deeper areas should be filled first, compacting the new mortar in several <br /> layers. The back of the entire joint should be filled successively by applying <br /> approximately .25 inch of mortar, packing it well into the back corners. This <br /> application may extend for several feet. As soon as the mortar has reached <br /> thumb-print hardness, another .25 inch layer of mortar-approximately the <br /> same thickness--may be applied. Several layers will be needed to fill the joint <br /> flush with the outer surface of the brick. It is important to allow each layer <br /> time to harden before the next layer is applied; most of the mortar shrinkage <br /> occurs during the hardening process and layering thus minimizes overall <br /> shrinkage, <br /> <br /> 2. The rate of hardening can be controlled by dampening the brick and the old <br /> mortar before beginning to fill the joint, but free water or excessive dampness <br /> in the joint should be avoided. Too much water will delay the tooling or cause <br /> excess shrinkage; too little water will be absorbed from the mortar before it is <br /> properly set, thus reducing bond strength. <br /> <br /> 3. When the final layer of mortar is thumb-print hard, the joint should be tooled. <br /> Proper timing of the tooling is important for uniform color and appearance, ff <br /> tooled when too soft, the color will be lighter than expected, and hairline <br /> cracks may occur; if tooled when too hard, there may be dark streaks called <br /> "tool burning," and good closure of the mortar against the brick will not be <br /> achieved. <br /> <br /> 4. Joint profile: Match existing original profile for both horizontal and vertical <br /> joints. <br /> <br /> 5. If existing original bricks have worn, rounded edges, recess the final mortar <br /> slightly from the face of the bricks. This treatment will help avoid a joint <br /> visually wider than the actual joint width; it will also avoid creation of a <br /> large, thin feathered edge which is easily damaged, thus admitting water. <br /> <br /> 6. After tooling, remove excess mortar from edges of joints by brushing with a <br /> bristle brush. <br /> <br /> Section 04200 <br /> Page 5-6 <br /> <br /> <br />