Page 144 - Construction Waterproofing Handbook

ABOVE-GRADE WATERPROOFING 3.33
Surface preparations of high-alkali substrates include acid washing with 5 percent
muriatic acid or primer application. In some cases, extending curing time of concrete or
stucco substrates will effectively lower their pH. Immediately after application stucco has
a high pH, but it has continually lower pH values during final curing stages. New stucco
should cure for a minimum of 30 days, preferably 60–90 days, to lower the pH. This also
allows shrinkage and thermal cracks to form and be treated before coating application.
Sealant installation should be completed before applying elastomeric coating to pre-
vent joint containment by the coating. This includes expansion and control joints, perime-
ters of doors and windows, and flashings. Small nonmoving cracks less than 16 in wide
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require filling and overbanding 2 in wide with a brushable or knife-grade sealant material
(Fig. 3.14).
Cracks exceeding 16 in that are also nonmoving joints should be sawn out to approxi-
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mately a 4-in width and depth and filled with a knife-grade sealant, followed by over-
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banding approximately 4 in wide (see Fig. 3.15). Changes in direction should be reinforced
as shown in Fig. 3.16.
Overbanding (bandage application of a sealant) requires skilled craftspeople to feath-
eredge banding sides to prevent telescoping of patches through the coating. Thick, unfeath-
ered applications of brushable sealant will show through coating applications, providing
an unacceptable substrate appearance.
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Large cracks over 2 in wide that are nonmoving, such as settlement cracks, should be
sawn out, and proper backing materials applied before sealant installation (Fig. 3.17).
Fiberglass mesh in 4-in widths can be embedded into the brushable sealant for additional
protection.

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FIGURE 3.14 Crack repair, under ⁄ in, for elastomeric substrate preparation. (Courtesy
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of Neogard)

FIGURE 3.15 Crack repair, over ⁄ in, for elastomeric substrate preparation. (Courtesy of Neogard)
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16