Be on Your Guard
SBCA Provides Design Tips for Guard Support Assemblies in the 2024 IRC
By Greg Greenlee, P.E. and Sean Shields
AS ADOPTION OF THE 2024 INTERNATIONAL Residential Code (IRC) spreads, component manufacturers (CMs) are facing an important new structural design consideration related to guard supports around stair openings, lofts, balconies, and other elevated walking surfaces (Figure 1). Section R502.11 of the 2024 IRC establishes new provisions for minimum framing, bracing, and reinforcement requirements for floor systems supporting guards, while also requiring that the effects of the guard loads be specifically considered in the design of the edge member when trusses or I-joists are used. These new provisions are intended to address long-standing concerns about the ability of floor systems to adequately resist the torsional and overturning forces created when guards are subjected to required code loads.
Recognizing the significant impact these code changes will have on CMs, the Structural Building Components Association (SBCA) has taken a proactive role in helping manufacturers understand and adapt to the new requirements. Through the development of its guidance document, IRC Floor Framing Guard Assembly Support Recommendations, SBCA is providing practical design recommendations tailored for wood floor truss applications. The goal is to help all stakeholders better coordinate guard support details early in the design process, rather than relying on field modifications after construction has already begun.
SBCA’s guidance underscores the fact that guard support can no longer be treated as an unconnected trade responsibility separate from floor member design. Do CMs undertake floor system design? No. However, the new code provisions now require that the floor member must consider the guard loading. To accomplish this, component manufacturers may need to proactively address the situation.
Industry Action
In the fall of 2021, the Stairbuilders & Manufacturers Association (SMA) introduced a significant change to the 2024 International Residential Code (IRC) to address what they viewed as a long-standing structural safety issue involving guard post connections at the edges of floor systems. During the ICC code hearings, SMA argued that floor systems, including those constructed with engineered wood products, such as floor trusses and I-joists, were rotating or failing too often when guards were subjected to required code loads. Although these floor systems were structurally code-compliant, they often lacked sufficient edge reinforcement to properly resist the torsional forces created when a 200-pound load was applied horizontally outward at the top of a guard assembly.
At issue is the fact that stair and guard installers frequently arrive on projects after finishing materials are already installed, leaving little project personnel visibility into whether the underlying framing is capable of supporting guard loads. In many cases, installers improvised field fixes by adding blocking or reinforcement after the fact, providing a solution that may or may not have been adequate. SMA viewed this as a serious gap in the code that created unnecessary safety risks and inconsistent construction practices.
SMA organized an industry-wide task group that included engineers, truss and I-joist manufacturers, builders, hardware manufacturers, railing fabricators, and stair builders. Working collaboratively, the group developed a proposal that was ultimately approved and incorporated into Section R502.11 of the 2024 IRC. SMA is currently advocating for early adoption of these changes by local jurisdictions to improve guard safety prior to widespread adoption of the 2024 IRC occurs.
CMs, truss technicians, building designers, and framers can no longer treat guard attachment locations as something completely outside their scope of work.
SBCA Guidance
The IRC provision explicitly states that when trusses or I-joists are used as edge framing members supporting guards, “the effects of the guard loads shall be specifically considered in the design of the edge member.” In practical terms, this means CMs, truss technicians, building designers, and framers can no longer treat guard attachment locations as something completely outside their scope of work. Instead, the guard assembly and floor framing system must be coordinated early in the design process to ensure that a complete structural load path exists.
The changes to the IRC create an important new requirement for floor framing systems that support guards around stair openings, balconies, lofts, and other elevated walking surfaces. While the code introduced prescriptive framing solutions for dimensional lumber, glued-laminated timber, and structural composite lumber floor systems, SBCA has developed additional guidance specifically tailored for component manufacturers for wood floor truss applications entitled, IRC Floor Framing Guard Assembly Support Recommendations, which can be found on SBCA’s Center, kcenter.sbcacomponents.com.
SBCA’s guidance explains that guards are required by Section R502.11 to resist a concentrated 200-pound load applied horizontally outward and vertically downward at any point along the top rail. These forces create significant overturning moments at the base of guard posts that can twist or rotate perimeter framing members if they are not properly reinforced or braced. The issue becomes especially important with engineered floor systems because open-web floor trusses and I-joists behave differently than solid sawn lumber members when subjected to torsional loading.
To help component manufacturers comply with the new requirements, SBCA’s guidance provides several prescriptive framing recommendations for floor truss systems. The document identifies three common floor truss configurations and outlines practical solutions for each. These include trusses spanning parallel to the edge member (Figure 2), hanger-supported bottom chord bearing trusses spanning perpendicular to the edge member (Figure 3), and bottom chord bearing trusses spanning perpendicular to a bearing wall (Figure 4). The third option is highlighted as particularly useful when guard post locations are not known prior to floor system installation.
Properly detailed roll braces and blocking help transfer these loads into the floor diaphragm rather than forcing the perimeter truss alone to resist the torsional force.
The recommendations are based on several defined assumptions, including a 200-pound outward load, a maximum guard height of 44 inches, maximum post spacing of four feet, and minimum floor truss depths of 9¼ inches. SBCA also stresses the importance of roll bracing and diaphragm action in resisting the torsional forces generated by guard loads. Properly detailed roll braces and blocking help transfer these loads into the floor diaphragm rather than forcing the perimeter truss alone to resist the torsional force.
Another major focus of this guidance is the connection between the guard post and the framing member itself. SBCA warns that many common construction practices may not adequately account for the forces imposed at this connection. Whether or not the guard posts are mounted to the top or side of the framing, the fasteners connecting the post base to the perimeter member must have adequate withdrawal and shear capacity. Responsibility for designing these connections typically lies with the building designer or guard assembly supplier, but component manufacturers still play an important role in ensuring that the framing system can properly support the applied loads.
The guidance also addresses an additional design consideration when the guard assembly doubles as a handrail, or when an inspector believes a guard system should be treated as a handrail. In those situations, IRC Table R301.5, footnote i requires the assembly to resist both a horizontally inward and horizontally outward load. SBCA notes that additional hardware, such as straps installed at the bottom chord of the floor truss, may be necessary to properly transfer these forces.
Bottom Line
SBCA’s recommendations emphasize communication and coordination. CMs, building designers, guard assembly suppliers, and framing contractors should discuss guard layouts and installation details early in the project. Further, CMs should call out roll braces and include guard support details directly on truss placement diagrams to help avoid field improvisation and reduce the likelihood of inspection failures or unsafe installations. Figures addressing this condition can be found in the new guidance document (Figures 5 and 6).
As jurisdictions across the country begin adopting the 2024 IRC, SBCA’s guidance provides CMs with a practical roadmap for adapting floor truss designs to satisfy these new code requirements.
Access more SBCA technical resources and guidance on SBCA’s Knowledge Center: kcenter.sbcacomponents.com.