Masonry Magazine October 1988 Page. 19
Weep Holes
Points where masonry walls are vulnerable to moisture are at grade line, sills and heads of openings, spandrel beams and at parapet walls. Requirements will vary for areas of different rainfall and wind pressures; and where exposure is slight, internal flashing, such as lintel or sill flashing may be eliminated. Typical flashing details are shown in Figure 3.
Staining
Staining, particularly on light-colored surfaces, can destroy the appearance of an otherwise attractive structure. In some buildings staining can be noticed below sills where concentrations of dirty water, washed from windows and wall areas above, is deposited. Other sources of staining include rust deposits where metal brackets, vents, railings, etc. are attached to the wall. Staining of the type described above can be prevented by considering a few simple details. Sills and other projections should be carried out at least 1" from the face of the wall and should be provided with a drip notch or groove on the underside to keep the water from running back under the sill and down the face of the wall.
Cleaning
Surface treatments which clean the wall as well as create subtle changes in its appearance include sand blasting and acid washing. Sand blasting will tend to round off aggregate particles at the surface, thereby creating a satiny sheen when light strikes the surface of the wall. Acid wash, although not generally recommended for concrete, can be effectively employed with customized concrete masonry. A weak acid wash removes laitance from the surface and leaves exposed aggregate particles sharp and angular. When light strikes the wall that has received an acid wash, the wall appears to have a much greater depth of color, sparkle, and life. A stronger acid wash yields a darker background or aggregate color. The "weak" acid for use with concrete masonry would consist of 1 part of muriatic acid to from 6 to 10 parts of water. The "strong" acid would consist of 1 part of muriatic acid to 3 parts of water. Of course, the wall surface should be wetted down prior to the application of acid and thoroughly rinsed afterwards.
Some manufacturers of customized masonry units have found it advisable to recommend coating the wall with one of the transparent water repellant coatings; the purpose of the coating would not be to waterproof the building, but rather to maintain a clean appearance. The transparent coating, while tending to shed water, would also prevent small dirt and soot particles from entering the surface and contributing to a stained appearance.
Summary
Customized concrete masonry construction possesses many advantages over competitive building materials. Among these are local availability and immediate delivery which eliminates costly delays, readily available assistance in problem solving and other special requirements, and more importantly, cost. In addition, the owner is assured of a building unique in design and appearance.