Page 358 - Construction Waterproofing Handbook

8.18 CHAPTER EIGHT
Only premixed materials specifically manufactured for tuck-pointing should be used.
These dry mixed cement and sand-based products contain proprietary additives for effec-
tive bonding and waterproofing, and are nonshrinking. Materials higher in compressive
strength than the masonry units are not recommended. If joints are stronger than the
masonry, spalling of masonry units during movement in the wall system will occur.
Materials should be mixed using only clean water in amounts specified by the manufac-
turer. Pointing materials are available in premixed colors, or manufacturers will custom-
match existing mortar. Field mixing for color match should be prohibited, as this results in
inadequate design strength and performance characteristics.
Pointing mortar must be applied using a convex jointer that compresses and compacts
material tightly into joints and against sides of masonry units. This creates an effective
waterproof mortar joint. The tooler or jointer should be slightly larger than joint width, and
enough mortar should be placed in joints so that after jointing, excess material is pushed
from joints. This ensures that joints are properly filled to capacity. Figure 8.14 summarizes
the steps involved in tuck-pointing.
After initial mortar set, joints should be brushed or scraped to remove fins formed by
applying this material. Finished joint design should be concave or weathered for longevity
and weathertightness. Refer to joint design in Chap. 10.
Priming of joints and bonding agents is not required. Dry mixes supplied by manufac-
turers contain all necessary components. Pointing should not be applied in conditions
under 40°F or over extremely wet surfaces.

FIGURE 8.14 Tuck-pointing processes.

FACE GROUTING

Certain restoration projects include deteriorated masonry units requiring remedial proce-
dures for both joints and masonry units. In a process referred to as face grouting or bag
grouting, a cementitious waterproofing material is brushed and scrubbed into mortar joints
and masonry faces. This grout is then brushed off just before complete curing of grout.
Grout materials are cement- and sand-based products with proprietary waterproofing
chemicals and bonding agents. Some materials contain metallic additives that may change
the color of a substrate when metallic materials begin oxidizing. Manufacturer’s data
should be reviewed, to judge product suitability for a particular installation.