The 2016 TMS 402/602 Masonry Code and Specification
By Richard M. Bennett
The 2016 TMS 402/602 Masonry Code Requirements for Masonry Structures and the TMS 602 Specification for Masonry Structures were recently published. The 2018 International Building Code (IBC) will adopt this code and specification. It typically takes several years for jurisdictions to adopt the latest edition of the IBC, so it will be a few years before the code is legally adopted. However, there are some changes that will benefit masonry designers and mason contractors, and with approval from the local building authority, those can be implemented now.
Although codes and specifications seem to be increasing in length, the 2016 TMS 402/602 code is a few pages shorter than the 2013 edition, a trend the committee hopes to continue. The next edition of the code will be in six years instead of three, or in 2022. This change recognized the burden on the industry when codes change too frequently and has been welcomed by designers and contractors.
Prior to delving into the 2016 TMS 402/602 Masonry Code, two changes in the 2013 edition that have a positive impact on masonry construction are reviewed. One change relates to the first course of masonry. Previous editions had restricted the first bed joint to be between 1/4 inch and 3/4 inch. This did not match foundation tolerances and potentially created problems for the contractor. Based on testing performed for the Concrete Masonry Association of California and Nevada and the Masonry Institute of America, the TMS 602 specification was revised to allow the initial bed joint to be up to 1 ¼ inch thick when the initial course is fully grouted. (See Figure 1, p. 15.) While this may not take care of every case in which foundations are grossly out of tolerance, it does provide some relief.
The other major change in the 2013 edition of TMS 402/602 relates to the strength of the masonry. First ASTM C90 was revised to increase the strength of concrete masonry units (CMU) from 1,900 psi to 2,000 psi. By itself, this change is not significant. More important, a recalibration of something called “the unit strength method” in TMS 602-13 occurred, which determines f’m value, the specified strength of the masonry assemblage. Previously, the value of f’m was 1,500 psi for units meeting the 1,900 psi strength of ASTM C90 and laid with type S mortar.
TMS 602-13 increased f’m to 2,000 psi for units meeting the new 2,000 psi strength of ASTM C90 and laid with type S mortar. This higher strength results in the masonry being used more efficiently. A contractor should be aware of this, because current plans and specifications are likely based on the former unit strength method. With stronger units and the new unit strength method, meeting higher f’m values specific on some jobs is easier, perhaps without the added expense of prism testing.
Many of the changes to 2016 TMS 402/602 Masonry Code are technical changes related to design, but will have a positive effect on masonry construction. One change is related to anchor bolts. The TMS 402-16 relaxed anchor bolt requirements, providing greater capacity for anchors loaded in combined shear and tension.
In addition, the shear strength of anchor bolts, based on the crushing capacity of masonry surrounding anchor bolts, was increased. Outside masonry codes, the loading standard (ASCE 7-16) was revised to reduce the required loads that anchor bolts must be designed to resist. All of these changes mean a reduction in the number of anchor bolts required. In one trial design, the number of required anchor bolts was cut in half.
A second major technical change to TMS 402 was the addition of shear friction provisions. Testing has shown that some masonry walls are susceptible to sliding at the base during a strong earthquake. The shear friction provisions address this possibility. From a construction perspective, the code defines two surfaces. A “rough” surface is concrete with an unfinished surface, or concrete with a finished surface that has been intentionally roughened. The commentary states that concrete roughened to a full amplitude of 1/16 inch meets this requirement. A “smooth” surface is finished concrete. From a shear friction viewpoint, a “rough” surface is better.
There were several changes in the veneer provisions. The prescriptive veneer anchor requirements were changed from a maximum cavity width of 4 1/2 inches to 6 5/8 inches under some conditions. The larger cavities do require more robust anchors, including ¼-inch diameter barrel anchors, and plate and prong anchors with minimum thickness and dimensions.
The motivation for this change was the ever-increasing energy code requirements, which in some areas is being met by insulation of 3 or even 4 inches. The small change from ½ inch to 5/8 inch was due to 5/8 inch sheathing increasingly being used over wood and steel stud backing. Although these larger cavities could have been used before, they required specific design.
The prescriptive requirements enable masonry veneer to remain a competitive cladding system and shows the industry commitment to respond to changing building performance requirements. From a materials perspective, TMS 602-16 now allows cast stone conforming to ASTM C1364 and manufactured stone conforming to ASTM C1670 to be used for appropriate veneer applications.
Figure 1: Reprint of TMS 402-16 Figure SC-9 showing permitted initial bed joint thickness for walls with the first course fully grouted
The 2013 TMS 402/602 had three quality assurance tables (Quality Assurance Level A, B, and C), and the tables were repeated in both the code (TMS 402) and the specification (TMS 602). For the 2016 edition, the tables were removed from TMS 402, and TMS 402 now just references TMS 602. This avoids duplication and the possibility for conflicting requirements.
The tables were also modified so that there are now two tables, one table for Minimum Verification Requirements, and one table for Minimum Special Inspection Requirements. This approach segregates minimum test requirements from the inspection provisions. It also keeps the required tasks consistent and removes the duplicative listing of Reference for Criteria between QA Levels B and C. Additionally, the QA levels were changed from A, B, and C to 1, 2, and 3, primarily to avoid confusion of “C” for Level C and “C” for Continuous.
While not requiring masonry testing, TMS 602 was changed to say that, if testing is required, only qualified testing technicians are permitted to conduct the tests. Masonry tests being performed by technicians who are not familiar with masonry or masonry tests has been an unfortunate experience for many of us. The result is sometimes-poorly executed tests, leading to erroneous results that can slow down or even stop masonry projects.
Thus, if masonry testing is to be performed, it needs to be conducted by someone familiar with masonry and those specific tests. Commentary was added to note that those certified as Masonry Testing Field (MFTT) or Laboratory (MLTT) Technicians by the American Concrete Institute (ACI) are considered qualified.
The Masonry Society (TMS) and other standards-writing organizations value input from contractors and others using the standards that they produce. Contractors who are members of TMS assist in ensuring these standards are reasonable, yet safe. TMS encourages your participation to ensure your views, opinions and ideas are considered. For additional information, visit the TMS website at www.masonrysociety.org.
Richard Bennett is a Professor of Civil and Environmental Engineering at the University of Tennessee, Knoxville. Dr. Bennett has been active in developing the TMS 402/602 Masonry Code. He was vice-chair of the 2013 committee, chair of the 2016 committee, and is currently 2nd vice-chair of the 2022 committee. He can be reached at rmbennett@utk.edu.
