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Two general types of ashing in masonry construction. External flashing prevent moisture from penetrating into the masonry wall at its exposed top or where it Internal flashing (also known as concealed pr through-wall flashing) catch penetrated a masonry wall and drain it through weep holes back to home to the exterior. The external ashing at the intersection of a at roof and a wall parapet is usually constructed in two overlapping parts, a base flashing and a counter flashing of cap flashing. This makes installation easier and allows for some movement between the wall aunt roof components. Often the base ashing is formed by the roof embarrassing itself. The base ashing is normally turned up for a heights of at least 8 inches (200 mm). The counter ashing is embedded in the masonry wall above the base ashing and extends downward, lapping over the base ashing. Counter ashing are often made in two interlocking pieces, making them easier to install and easier to remove when the roof membrane must be replaced. Internal ashing are installed by mason as they construct the wall. We have already discussed the internal ashing that is placed that is placed at the bottom of the wall cavity. Additional ashing are required at every location where the cavity is interrupted: at heads of windows and doors, at window sills, at shelf angled, and at spandrel beams. Where an internal ashing crosses the wall cavity,it should be turned up 6 to 9 inches ( 150 225 mm) at the back face of the cavity and penetrate the inner why the by at least 2 inches (50 mm). In this manner, water draining down the cavity is intercepted by the ashing and directed toward the exterior of the wall. Example of this internal ashing can be seen in Figure. If the cavity is backed up by concrete beam or wall, it may terminate in a regret, a horizontal slot formed in the face of the concrete, as shows on the face of the aright-hand side of Figure . At the ashing should be carried at least 3/4 inch (19 mm) beyond the face of the wall and turned down at a 45-degree the ashing drips free of the wall, rather than being drawn under the ashing by capillary action and returning into the watt. It is common but dangerous practice to terminate the ashing just inside the face of the wall in order to hide the ashing; this can cause signi cant amount of water to be reabsorbed by the wall underneath the ashing.
Flashing may be made of sheet metal, modi ed asphalt membranes, plastic, rubbers or composite sheet. Sheet meta ashing are the most durable and the most expensive. Copper and stainless steel are the best; galvanized steel eventually rusts and disintegrates. Aluminum and lead are unsuitable for ashing in masonry wall because they react chemically with mortar. Asphaltic ashings are made of polymer modi ed asphalts laminated to plastic backing. Most are manufactured with preapplied adhesive on one side, for which reason they are frequently referred to as self-adhered flashing. In comparison to metal ashing, they can be more easily shaped and sealed at corner and laps. They are often use in combination with sheet metal. The sheet metal can support the exible asphaltic membrane where it spans the wall cavity and can extend beyond the outer face of the wall to form the recommend drip.
A solid masonry wall is a good conductor of heat, which is another way to say that it is a poor insulator. In many hot, dry climates, the capacity of an unisulated masonry wall ti tore heat and retard its passage keeps the inside of the building cool during the hot day and warm during the cold night. But in climates with sustained cold or hot season, measures must be taken to improve the thermal resistance of masonry walls. The introduction of any empty cavity into a wall improve its thermal insulating properties considerably, but not to a level fully suf cient for cold climates. There are three general ways of insulating masonry walls: on the out side face within the wall, and on the inside face. Insulation on the outside face is a relatively recent development.
25 Feb, 2018
NIMS offers a diverse and vibrant community where students can not only excel academically but also grow personally through engaging experiences and supportive networks. Help other students by share your experiences at NIMS.