Besides mortar being used to adhere thin-brick units, adhesives can also be employed. In most cases, the adhesive is used in combination with a grooved panel to set the brick in the correct location. Special adhesives are made to perform in this system and are usually proprietary, depending on the panel manufacturer. Panels are screwed to the substrate and brick are adhered to the panel with adhesive or held from sliding by ridges or tabs while the adhesive dries. The joints are then filled with mortar.
Precast concrete with brick facing, known as brick-faced precast panels, have been used for decades and have a good track record. In this system, the thin brick are placed into forms face down and cast integrally with concrete. The concrete panel will be designed for the appropriate loads and incorporate reinforcing steel. The units themselves may be full-depth or half-depth (soaps), but are most commonly thin units. The units may or may not have a dovetail on the backing, although many precasters request it. Since concrete can act as a WRB and air barrier, it does not need these layers, but the joints should be treated to provide continuity to the air barrier.
The Precast/Prestressed Concrete Institute (PCI) has some additional requirements their members use in addition to those of BIA and ASTM. Although these can be followed, BIA feels these PCI requirements do not provide any additional protections or performance. For the association, ASTM C1088 is sufficient.
As mentioned, the thin brick are set into rubber forms to keep them in place as concrete is poured over the backing. The tolerance of the unit is important so the concrete does not run onto the face of the brick. After the concrete cures, the wall is set upright and any forms are removed. The rubber form creates mortar joints. While these could be left unfinished, it is generally recommended the joints be filled with mortar. When cured, the panels are erected or lifted into place by a crane as you would do with any precast panel. The size of the panels may be dictated by transportation issues or distance between expansion joints. The panels are then attached to the frame with anchors.
Conclusion
In summary, one should design thin-brick veneer systems as barrier walls, as this leads to the required water protection measures. It is important to choose the appropriate system according to its use, while remembering not all backings perform the same.
Thin brick should be specified according to ASTM C1088, along with the appropriate mortar. Since this system does not have the redundancies of full-brick systems, design/construction professionals must pay more attention to the details. Further, additional field observation may be required to ensure proper installation.
Brian Trimble has more than 25 years of experience in the masonry industry, assisting design professionals in the design of brick and masonry structures. He is a frequent lecturer to local, regional, and national construction industry groups. He has authored many articles and papers on various masonry subjects. Brian has worked at the Brick Industry Association (BIA) for over 20 years, serving in various positions. He previously worked for a brick manufacturer and the International Masonry Institute (IMI), and now heads up architectural and builder outreach in the 17-state Midwest/Northeast Region for BIA. He can be contacted by e-mail at btrimble@bia.org.
I have seen a few buildings recently that use thin brick paneling and I have wondered what they’re all about. It’s interesting how you point out that they need to be installed with extra precision to ensure that they are as sturdy as possible. I imagine that it would be a good idea for anyone thinking of using this to do their research and look for a company that has good reviews and has done well on previous jobs.
Just a note for your web developer: your “Figure 1” appears to have a couple of mistakes in it; for both columns (“adhered veneer” and “anchored veneer”), the 4th and 5th lines both state the parameter of “maximum unit thickness”. I suspect that one of them should read “minimum unit thickness”.
Within TMSn402’s section on adhered veneers, there are some general design requirements for all types of brick veneers, including water-resistant membranes, flashing, weeps and movement joints. Thank you so much for sharing the information.