Bonding with Masonry 2026: Q1

Words: David Biggs

This issue’s questions come from a Mason Contractor and an Engineer. What questions do you have? Send them to info@masonrymagazine.com, attention Technical Talk.

Q. A Mason Contractor states they were asked to construct a brick veneer on a multi-story project after the concrete frame was partially erected. The shelf angles were designed to be supported by the concrete structure. However, there was no allowance for the misplacement of the shelf angles due to the concrete floor being out-of-tolerance. What are the options?

A. This is a very good question! To maintain the anonymity of the Contractor, we will discuss this topic using a detail like the as-built detail you described. In a follow-up communication, you stated the concrete floor supporting the shelf angle on one floor was out-of-plumb outward by just over 2 inches at a level approximately 90 feet above grade. The CMU backup wall was placed plumb. Although not shown, the veneer bows back to plumb above and below the angle.

The allowable site tolerances for concrete frame construction are not consistent with those for masonry standards. For example, for a shelf angle at 60 ft above the ground level, the masonry standards, TMS 602-22, Article 3.3G, 2.b., allow the wall to be out-of-plumb +/- ½ inch. However, for concrete, ACI 117, Specifications for Tolerances for Concrete Construction and Materials, allows the concrete frame to be out-of-plumb by +/- 1 inch. So, for your project, the concrete is clearly out of tolerance and was not remediated.

For many projects, it is unrealistic to await completion of a concrete frame, then check for tolerances, and remediate before the veneer is started. This decision is usually schedule-driven by the general contractor or construction manager. But it comes with consequences. Ideally, the tolerances should be checked before concrete placement. It is also unreasonable to direct you to proceed and then reject the final project.

In your case, the construction manager asked you to build through the problem area instead of having the concrete subcontractor remediate their mistake. That then created a visually objectionable veneer. Without performing removals and correcting the underlying mistake, the option seems limited to evaluating the shelf angle support and the veneer ties, and the corbelling limitations. The visual issues cannot be corrected.

The prescriptive limitations for corbelling are needed to bow the veneer around the offset shelf angle. Figure CC-5.6-2 allows up to 1 inch offset. If the offset is greater, the corbelling needs to be engineered.

For future projects, this possible scenario could be discussed during pre-construction, including:
a. What inspection procedures are in place before concrete placement to avoid this from occurring? How are the tolerances being checked?

b. What flexibility is built into the details to accommodate the differences in allowable tolerances from the frame to the veneer? Are shims built into the shelf angle support to allow the angles to move inward? Are the bolts supporting the shelf angle have adequate length and sufficient capacity to allow additional shims for the shelf angle to move outward? Are the veneer anchors and ties capable of variations in tolerances? Can various-length veneer ties be provided to avoid delays?

Summary:
1. Masonry veneer tolerances are different from both steel and concrete framed structures.
2. Masonry shelf angle support details should accommodate the industry tolerance differences between the masonry veneer and the frame that supports it.
3. Frame tolerances should be checked during the erection of the frame. Corrections should be made before veneer installation.

Q. An Engineer asks whether GFRP bars can be used in masonry construction. Their use is becoming common in concrete construction. Is it also allowed for masonry?

A. Thank you for the question. Starting with the 2022 TMS 402, Building Code Requirements for Masonry Structures, and TMS 602, Specifications for Masonry Structures, which are masonry standards in the International Building Code (IBC), FRP bars are allowed, but for very restricted applications. So, the answer to your question is yes, but the limitations are considerable.

In TMS 402, Appendix D, Glass Fiber Reinforced Polymer (GFRP) Reinforced Masonry allows GFRP use only in non-participating walls constructed of concrete or clay masonry. That means no shear walls. In addition, walls with GFRP reinforcement cannot be used for walls that support service level loads over 200 lb. per linear foot, any wall with net tension, or columns.

Likely applications are where aggressive corrosion or electromagnetic effects may exist in partitions, retaining walls, walls in severe environments such as coastal construction, seawalls, chemical plants, near MRI equipment, or near high voltage electric cables or transformers. The standard allows the GFRP to be used for lintels within these walls, too. However, GRFP bars cannot be used for either shear reinforcement or compression reinforcement.

TMS 402 limits the maximum size bar to #6.

If a designer wants to use GFRP mixed with steel reinforcement, the standard requires only one type of reinforcement for each type of loading. An example given in the commentary is the GFRP bars being used for out-of-plane flexure for the walls, and steel horizontal joint reinforcement being used for crack control.

The limitations are primarily a result of a lack of testing with masonry. Future editions will be expanded as the research develops. The appendix will ultimately become a chapter in the code.

As to materials, TMS 602, Article 2.4C. GFRP Reinforcing Bars limits the bars to solid deformed GFRP reinforcing bars that conform to ASTM D7957/D7957M. Smooth bars or hollow bars are not permitted.

The masonry units, mortar, and grout used in the construction are the same as those used in reinforced masonry with steel reinforcement.

Summary:
1. Glass fiber reinforcement has officially been introduced in the masonry standards TMS 402/606 and the 2024 IBC.
2. The standards allow partitions and non-load bearing walls and their lintels to be designed with GFRP reinforcement.
3. The wall construction and materials are like those of walls constructed with steel reinforcement. Bar size is limited to #6.

Thank you again for following this column. Remember, by bonding, we get stronger! Keep the questions coming. Send them and your comments to info@masonrymagazine.com, with attention to Technical Talk. If you have missed any of the previous articles, you can find them online for Technical Talk, Bonding with Masonry at Masonry Design magazine.

David is a PE, SE with Biggs Consulting Engineering, Saratoga Springs, NY, USA (www.biggsconsulting.net), and an Honorary Associate Professor with the University of Auckland, NZ. He specializes in masonry design, historic preservation, forensic evaluations, and masonry product development.

Keywords for this issue: shelf angles, tolerances, frames, GFRP, partitions, lintels

Bonding with Masonry 2026: Q1

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