TB-0005B — Mortar Joints and the DRY-BLOCK® System

Mortar joints in masonry construction can account for up to 15% of the surface area of a wall. To maximize water repellency, selecting a weather-resistant mortar joint profile is an important design consideration. Below are a few common mortar joint profiles. For exterior DRY-BLOCK® applications a “V” or Concave profile results in a well-compacted joint and is strongly recommended. Weathered, flush, raked, struck, beaded, or weeped joint profiles provide poor water resistance and are not recommended for exterior applications.

When tooling a joint the mortar should be thumbprint hard. A joint is thumbprint hard when it will retain the imprint of a thumb. This will aid in developing a smooth dense surface, create intimate contact between the mortar and the adjacent masonry unit and reduce the potential for hairline cracks.

Since DRY-BLOCK provides water repellent properties to cured mortar, premature drying of the mortar will activate these properties and subsequent hydration will be hindered. Proper curing and construction techniques can be found in technical literature published by the National Concrete Masonry Association (www.ncma.org).

* Not recommended for exterior use.

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Last Updated: 2023-06-28