Stack and decorative pattern masonry veneers always require joint reinforcement when constructed according to CSA A371-14. This is something addressed by CSA A371-14, Clause 8.1.3: This weak bond along the height of stack pattern masonry needs to be supplemented in order to ensure the veneer does not suffer cracking beyond what would be typically expected in a masonry veneer with a running bond pattern. Unreinforced masonry veneers built with stack pattern can display significant vertical cracking at the vertical and continuous mortar joints shortly after installation. Without sufficient unit overlap between adjacent courses in running bond construction, it has been observed through decades of field experience that continuous mortar head joints, when left unreinforced, are insufficient to hold the vertical “stacks” of units together and to resist even nominal movement within the wall due to moisture, temperature, or loading related strains. The use of the word “bond” is explicitly excluded from stack and decorative pattern terminology in the CSA Standards to avoid the implication that there is sufficient bond across continuous head joints alone. An explicit distinction was made in Canada to differentiate between running bond patterns and stack and decorative patterns. There is a common terminology misconception with use of the term stack bond from the perspective of Canadian Codes and Standards. Designers should consider the limitations for use of stack or decorative patterns in non-veneer walls contained throughout CSA S304-14. Stack or decorative patterns used in masonry walls other than veneers may also require additional design considerations and could be subject to explicit restrictions on their use for some applications. The purpose of this page is to highlight horizontal joint reinforcement requirements when selecting a stack or decorative pattern for a masonry veneer instead of a running bond pattern. The key consideration here is that stack and decorative patterns where less than 50 mm of the unit overlaps, are not considered to have sufficient bond in the horizontal direction alone and must be reinforced in the horizontal direction. There may also be “decorative patterns” of masonry where there is some unit overlap, but it is insufficient to be considered a running bond pattern. When there is no unit overlap from adjacent courses the term used is “stack pattern” and, in this case, head joints form a continuous vertical line in the wall. CSA S304-14 defines running bond patterns as those with head joints in successive courses that are horizontally offset at least 25% of the unit length. 50% running bond is when one-half of the unit overlaps the unit from an adjacent course), sufficient to provide bond in the horizontal direction of the wall. In masonry construction, a “running bond pattern” is the term given when masonry units overlap from course to course, typically expressed as portion of the unit length that overlaps (e.g. One option which has become increasingly popular across Canada is to change a running bond pattern to a stack or decorative pattern. Masonry also allows designers the creativity in determining how individual units will come together in a larger wall panel to form a desired aesthetic. Masonry veneers are known for being a high-quality building envelope material and providing exceptional durability.
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