Lipped bricks are frequently specified in brick masonry veneer wall construction to conceal the toe of steel relieving angles, which are typically located at each floor level to support the weight of the bricks above. These bricks have a unique design with a protrusion along one edge of their exterior face to hide the underlying angle, ensuring the horizontal joints at angle locations remain consistent in width with the surrounding mortar bed joints. Some designers prefer this to maintain visual appeal.
Brick, a fired clay material, is initially at its smallest size when it emerges from the kiln. Over its service life, it gradually increases in size due to moisture absorption, a slow and irreversible process known as ceramic expansion. Additionally, reversible in-plane expansion and contraction occur due to thermal changes in brick masonry during in-service conditions. To accommodate both vertical and horizontal expansion in brick masonry construction, it is common practice to incorporate appropriately spaced and positioned expansion joints in the facade design. Guidance on the size and spacing of these expansion joints can be found in industry standards such as ASTM International C 1472, Standard Guide for Calculating Movement and Other Effects when Establishing Sealant Joint Width, as well as publications from the National Concrete Masonry Association (NCMA) and the Brick Industry Association (BIA).
Horizontal expansion joints, often located at the relieving angles attached to the building structure, allow unrestrained vertical expansion in exterior cladding due to moisture and thermal changes, maintaining the wall’s structural integrity. These joints need to maintain an unobstructed gap between the shelf angle and the brick course directly below the angle. Rigid obstructions within the plane of the horizontal expansion joint can hinder cladding movement and create undue stress in bricks, angles, and building structural components.
If not properly detailed and/or constructed, lipped brick installations can lead to distress, often within a few years of construction. The unique shape of lipped bricks, along with the complexity of underlying wall details like through-wall flashing, can increase the risk of obstructions in the horizontal expansion joint. This can accumulate compressive stresses, eventually causing cracking, spalling, and out-of-plane displacement in the brick masonry, potentially leading to structural problems, instability, and water infiltration issues, which may increase the potential for freeze-thaw damage in colder climates.
If this distress occurs, repairs are needed to clear and replace the entire length of the horizontal expansion joints and damaged masonry. To reduce potential problems with lipped brick, the BIA offers guidelines for minimizing the visual impact of expansion joints and provides best practices for detailing lipped brick when chosen.
Alexandar J. Mlynarczyk, PE, is a senior associate with Wiss, Janney, Elstner Associates (WJE) in Princeton, N.J. He specializes in investigation and repair of the building structures. He can be reached at amlynarczyk@wje.com.
The opinions expressed in Failures are based on the authors’ experiences and do not necessarily reflect that of The Construction Specifier or CSI.
