For an interior “clean room” utilizing glazed masonry unit walls, how should mortar joints be specified to facilitate cleaning?

ANSWER: 

Glazed masonry units are a good choice for clean room walls because the glazed surface is relatively easy to clean.  Furthermore, glazed units (such as those complying with ASTM C7444 or ASTM C1262) are fabricated to be placed with 1/4-inch wide mortar joints while non-glazed units (such as those complying with ASTM C901 or ASTM C2123) are fabricated to be placed with 3/8-inch wide joints.  Narrower joints are preferred in a clean room because mortar is not as easy to clean as the glazed surface.  Larger masonry units, such as glazed concrete block or glazed hollow clay tile, are preferred to smaller masonry units, such as glazed brick, because the constructed wall has fewer mortar joints.

For mortar used with glazed concrete masonry units, the Portland Cement Association5 recommends adding a water-repellent admixture to the mortar to reduce absorption of the constructed mortar joints.

To improve resistance to biological growth, a mildewcide or fungicide that has been proven to be not detrimental to mortar properties may be added to the mortar that is used to set the glazed units.  Another option is to rake back the mortar joints after setting the units, and then pointing with a proprietary epoxy grout that is specifically formulated for this application.

Resources:

  1. ASTM C90 Standard Specification for Loadbearing Concrete Masonry Units
  2. ASTM C126 Standard Specification for Ceramic Glazed Structural Clay Facing Tile, Facing Brick, and Solid Masonry Units
  3. ASTM C212 Standard Specification for Structural Clay Facing Tile
  4. ASTM C744 Standard Specification for Prefaced Concrete and Calcium Silicate Masonry Units
  5. Jamie Farny, Portland Cement Association Market Manager Buildings

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