For the Brickyard Campus project, the TCNA Handbook on installation method W231/W241 for exterior walls with a waterproof membrane over a plaster substrate (scratch coat and mortar bed) as well as metal studs was specified. The handbook explains the tile assembly configuration, product types, methods, requirements, and standards for completing the installation. The method described in the handbook is an effective means for the architect
to provide thin briks installers with unambiguous instructions.
Quality assurance
QA is a useful tool to ensure appropriate products and methods are vetted in advance, thereby avoiding project delays. It can also be used to verify the application performs as intended during the installation process.
Much like other finish materials, thin brick has certain physical properties and tolerances. According to ASTM C1088, Standard Specification for Thin Veneer Brick Units Made From Clay or Shale, the maximum saturation coefficient (i.e. the ratio of absorption by 24-hour submersion in cold water followed by a five-hour submersion in boiling water) is an average of 0.78 for exterior grade thin veneer brick or maximum permissible warpage for maximum face dimension of 203 mm (8 in.) is 1.6 mm (1/16 in.) for Type TBX thin veneer brick.
The thin brick specified on the Brickyard project had to meet ASTM C1088. The thin brick veneer was specified to be tested per ASTM C67, Standard Test Methods for Sampling and Testing Brick and Structural Clay Tile. In particular, the project team wanted to ensure the 92 x 297 x 20-mm (3 5/8 x 11 5/8 x ¾-in.) thin brick met the sizing and warpage tolerances. This was important because of the different-sized windows and the design. The thin brick had to be within the allowable tolerances that is anticipated for the specified layout, such as:
- ground short edge dimensional tolerance of + 0 mm (0 in.);
- 2.4 mm (3/32 in.) for the 297-mm (11 5/8-in.) side;
- +/– 1.6 mm (1/16 in.) tolerance on the 92-mm
(3 5/8-in.) side; - thickness tolerance maximum of +/– 3.2 mm (1/8 in.);
- out of square tolerance maximum of +/– 1.6 mm (1/16 in.); and
- warpage maximum of +/– 1.6 mm (1/16 in.).
Thin bricks, considering their size, have a greater degree of allowable warpage than tile. Warpage contributes to tile lippage where one edge between two adjacent edges of a thin brick is higher or lower than the other. This creates a shadowing condition making a façade appear to be irregular under certain lighting conditions, which in this case, means relative to the position and exposure to the sun. So, excessive thin brick warpage not only makes for a more difficult installation, but also affects the appearance of the finished work. It was also specified to verify how the ceramic engobe coating covering the face of the thin brick would hold up over time.
Lesson learned
The QA process included visiting the thin brick manufacturer to inspect the plant, manufacturing process, and end product. The inspection team (without the thin brick consultant) visited the plant and was impressed with the manufacturer. As a result, the client did not perform the specified QA testing of the thin brick. Unfortunately, all 10,219 m2 (110,000 sf) of thin brick had to be returned post-delivery because they were out of tolerance in size and warpage. This caused disputes, delays, inconvenience, and loss of time. Implementation of a proper QA plan would have helped prevent this situation. Therefore, it is advisable to not assume anything and verify everything. The added cost for QA is cheap insurance.
Bond strength tests in the laboratory per ASTM C482, Standard Test Method for Bond Strength of Ceramic Tile to Portland Cement Paste, were also specified. This is not only a code requirement, but also important when considering the liability if a thin brick falls off a five-story building. It is a health and safety concern and due diligence should be employed to ensure the thin brick is properly attached to the structure. The California Building Code (CBC) 1405.10 Adhered Masonry Veneer, and 1411.2.1, Bond Strength and Tests, references ASTM C482 by requiring compliance with sections 12.1 and 12.3 of The Masonry Society (TMS) 402, Building Code Requirements for Masonry Structures/American Concrete Institute (ACI) 530, Building Code Requirements and Specification for Masonry Structures and Companion Commentaries/American Society of Civil Engineers (ASCE) 5, Building Code Requirements and Specification for Masonry Structures. Section 12.3.2.4 says adhesion developed between adhered veneer units and backing shall have a shear strength of at least 345 kPa (50 psi) based on gross unit surface area when tested in accordance with ASTM C482.
