T-bar Ceilings – A Structural Engineer’s Perspective in British Columbia
- Matthew Elgersma, P.Eng., P.E.
- Oct 13
- 16 min read
This document is intended to provide clarity on T-bar design in Canada and more specifically in British Columbia from an engineer’s perspective.
This document has several purposes:
It clarifies Thornfield Consulting Corp’s position on T-bar design,
It serves to provide other engineers with the resource for their T-bar design, and
It serves to educate our clients and the public on T-bar design.
Table of Contents
1. About
T-bar ceilings are everywhere—they can be found in doctor's offices, stores, residences, hospitals, schools, and office spaces.
T-bar offers several advantages as a ceiling system. It has excellent acoustic properties, helping to create a quieter space. It is also relatively easy to install compared to other ceiling types. Most importantly, it provides convenient access to mechanical, electrical, and plumbing (MEP) systems that may be located above the ceiling.
T-bar ceilings are used worldwide, meaning we have extensive data on how they perform under various conditions. One of the most well-documented conditions is earthquakes. Past earthquakes have shown that T-bar ceilings often fail. While their failure may not necessarily be fatal, falling tiles and tees can significantly obstruct a person's ability to exit a space quickly.
T-bar ceilings go by many names. Building codes often refer to them as acoustical tile or lay-in panels. However, for the purposes of this document, they will be referred to by their most common name: T-bar, a term derived from the T-shaped tees that form the ceiling grid.
At Thornfield Consulting, we’re often asked how T-bar ceilings should be designed and what the British Columbia Building Code actually requires. The answer isn’t always straightforward. Between the BCBC, CSA S832, and ASTM E580, there’s a maze of overlapping guidance, interpretations, and exceptions that can make even experienced professionals second guess what’s required.
This document clarifies Thornfield’s approach to T-bar ceiling design in British Columbia. It’s written for engineers looking for a clear framework, for architects seeking confidence that their projects meet code intent, and for clients who want to know their buildings are safe.
2. Codes
We will begin by determining which codes apply to T-bar design. This requires reviewing the relevant schedules and identifying the specific codes they mandate. From there, we can examine the codes referenced by the governing regulations, continuing the process as needed.
a) Schedules
At a basic level, schedules serve as an “Assurance of Professional Design and Commitment for Field Review.” Engineers signing off on T-bar ceilings typically provide a Schedule S-B/S-C[1] to the Architect of Record for the project. In this role, the engineer acts as a Supporting Registered Professional (SRP).
The engineer submits this schedule to the architect because the architect has typically provided a Schedule B[2] to the Authority Having Jurisdiction (AHJ). In this Schedule B, the architect often assumes responsibility for Section 1.6: “Structural capacity of architectural components, including anchorage and seismic restraint.” However, because most architects lack the structural engineering expertise required to design T-bar ceilings, they rely on the SRP to provide the necessary structural design and supporting documentation.
b) BCBC and VBBL
Schedule S-Bs state that “The applicable code is the British Columbia Building Code or the Vancouver Building By-law, hereinafter referred to as the Code”. The person signing off a Schedule S-B, also states that their “design and supporting documents [ ]substantially comply with the Code and other applicable enactments respecting safety except for construction safety aspects”.
This establishes that the governing code for T-bar ceiling design must be either the British Columbia Building Code (BCBC) or the Vancouver Building By-law (VBBL). Any design work must comply with these regulations.
Note: While the BCBC and VBBL are separate documents, they are highly similar. For the purposes of this document, references to the BCBC will also imply the VBBL where applicable. Direct code citations will be from the BCBC 2024.
c) BCBC as the Code to Rule Them All
The BCBC contains several clauses relevant to ceiling design and also incorporates multiple external codes that must be followed. However, a particularly significant clause is 1.5.1.2, which states:
“In case of conflict between the provisions of this Code and those of a referenced document, the provisions of this Code shall govern.”
From this, it follows that any standard referenced by the BCBC must align with its provisions. If a referenced standard conflicts with the BCBC, the conflicting clause cannot be followed.
The BCBC in Section 1.3 in Table 1.3.1.2, brings in one particular code relevant to ceiling design, namely CSA S832:14 Seismic risk reduction of operational and functional components (OFCs) of buildings. S832 is referenced in the Notes to Part 4 Structural Design in A-Table 4.1.8.18. which states:
Non-structural Components and Equipment. The failure or detachment of nonstructural components and equipment during an earthquake can present a major threat to life safety. The design requirements presented in Article 4.1.8.18. are intended to ensure that such components and their connections to the building will retain their integrity during strong ground shaking. Guidelines for the seismic risk reduction of such components are given in CSA S832, "Seismic risk reduction of operational and functional components (OFCs) of buildings."
From the note above, it is evident that the structural integrity of T-bar ceiling elements is addressed in Article 4.1.8.18. Additionally, it appears that CSA S832 provides further guidelines for risk reduction.
Notably, while the BCBC could have directly incorporated ASTM E580 – Standard Practice for Installation of Ceiling Suspension Systems for Acoustical Tile and Lay-in Panels in Areas Subject to Earthquake Ground Motions, it chose not to do so. This omission is particularly significant given that the BCBC references numerous other ASTM standards.
d) BCBC Article 4.1.8 Earthquake Loads and Effects
Clause 4.1.8.1 Analysis states that
1) Except as permitted in Sentence (2), the deflections and specified loading due to earthquake motions shall be determined according to the requirements of Articles 4.1.8.2. to 4.1.8.23.
From this clause, it can be seen that the deflections and loading of ceilings (covered in clause 18 as shown below) must be designed per the BCBC. The only exceptions as discussed in sentence two are “Where IE Fs Sa(0.2,X450) and IE Fs Sa(2.0,X450) are less than 0.16 and 0.03 respectively”. In that case, only a few requirements apply. Therefore, for these very low seismic zones, section 4.1.8.18 need not apply. However, we do not have areas in the lower mainland of BC which would fall into this zone.
In light of the fact that clause 4.1.8.18 applies in BC, we can now review its requirements.
Clause 4.1.8.18 Elements of Structures, Non-structural Components and Equipment states that
Except as provided in Sentences (2), (7) and (16), elements and components of buildings described in Table 4.1.8.18. and their connections to the structure shall be designed to accommodate the building deflections calculated in accordance with Article 4.1.8.13. and the element or component deflections calculated in accordance with Sentence (9), and shall be designed for a specified lateral earthquake force, Vp, distributed according to the distribution of mass.
The above clause informs us that the T-bar ceiling must be designed to take the seismic loads. The sentence does provide a few exceptions in sentence 2,7, and 16, but these do not apply, as we shall see below.
Sentence 2 states:
2) For buildings in Seismic Category SC1 or SC2, other than post-disaster buildings, seismically isolated buildings, and buildings with supplemental energy dissipation systems, the requirements of Sentence (1) need not apply to Categories 6 through 22 of Table 4.1.8.18
Since the lower mainland does not fall into SC1 or SC2, we must still design ceilings for seismic loads, even though they are in category 7.
Sentence 7 provides additional requirements for the connections and so does not remove the need for ceilings to be designed for seismic loads.
Sentence 16 provides additional requirements for determining the earthquake force in buildings with supplemental energy dissipation systems and so also does not remove the need for ceilings to be designed for seismic loads.
e) CSA S832 Seismic risk reduction of operational and functional components (OFCs) of buildings
Now that we’ve established that ceilings must be designed for the seismic loads as specified in Section 4.1.8.18 of the BCBC, we will look at the additional requirements in CSA S832: 14 Seismic risk reduction of operational and functional components (OFCs) of buildings.
Clause 1.1.1 of CSA S832 states “This Standard applies to OFCs in buildings with seismic hazards as defined in Article 4.1.8.1 of the NBCC.” Therefore, CSA S832 applies the ceilings.
Clause 1.3.1 of the same standard states that “This Standard does not address the integrity of the structural systems of buildings. Structural aspects are covered by the building codes and other publications referenced in Clause 2.” This would imply that structural aspects of the ceilings, e.g. loads, would not be covered by this standard. This clause is interesting as Annex I of the same standard gives an example of how to calculate the loads in a T-bar ceiling brace.
Section 5 covers “Design and procedure for OFCs in new buildings”. Section 5.3.3.1 states “Except as permitted in Clause 5.3.7 all OFC restraints and their connections shall be designed to resist a minimum lateral force calculated in accordance with Article 4.1.8.18 of the NBCC. See Annex F.” This again reinforces that the BCBC must be used for calculating and resisting ceiling forces.
Somewhat strangely, Annex I also says:
“Prescriptive methods outlined by the American Society for Testing and Materials (e.g., ASTM E580) and the Ceilings and Interior Systems Construction Association (CISCA) have proven effective in reducing the risk of suspended acoustic ceiling failure in an earthquake.”
This statement seems to attempt to provide an alternate to the methods in the BCBC, however it seems that this statement must be ignored in light of clause 1.5.1.2 of the BCBC.
The only times that ASTM E580 is referenced is in Section 2 Reference Publications, Section 9 OFC problems and risk mitigation procedures, and Annex I as mentioned above.
Section 9 includes Table 9 which details Typical OFC problems and mitigation techniques.
Table 9 is referenced by a few clauses, namely:
- Clause 8.2 which states:
The prescriptive method consists of the application of typical details published in selected industry associations’ guidelines and references that describe the design concepts and construction features that protect OFCs against seismic hazards. In this method, OFCs and their anchorages or restraints are assessed for compliance with the published standards and guidelines that are referenced in the Standard (see Table 9). Due consideration shall be given to Canadian seismicity, codes, and industry practice when applying those standards and guidelines.
- Clause 9.1 which states:
Typical problems and their mitigation techniques are listed in Table 9 for OFCs from each component category (architectural, building services, and building contents) defined in the Standard. These problems have been observed in past earthquakes and documented in damage reconnaissance reports. Therefore the list might not be exhaustive and require updating as more data become available from new earthquake occurrences around the world.
- And Clause B2.6 which states:
Based on the earthquake experience with respect to OFCs, Table 9 itemizes various problems noted or anticipated. This list is not exhaustive; the intent is to expand this list as more information becomes available.
From the above clauses, it can be seen that Table 9 does not appear to be something which must be followed. It is more of a compilation of issues and mitigation techniques that building owners can implement to improve the safety of their buildings. Clause 8.2 seems to imply the Table 9 can be followed as an alternative to the BCBC 4.1.8.18, but that is not the case as has been discussed at length above.
However, even if table 9 were a mandatory part of the code (it's not as it only provides “suggested mitigation techniques”) and was to be used alongside the BCBC, it still would not bring in the requirements of ASTM E580. This is because where the table mentions ASTM E580 as a way to mitigate damage to ceilings in an earthquake, it also says that “This is not a problem with light weight panels (less than 10 kg/m2).[3]” Nearly all ceiling tiles weigh less than 2 psf.
To summarize, given that Table 9:
Only provides “suggestions”,
Is only referenced as an alternative to the force-based methods,
and does not apply to ceilings less than 2 psf,
it can be reasonably concluded that the requirements of ASTM E580 do not apply in BC.
f) Feedback from the CSA S832 Code Committee
I reached out to the CSA S832 Technical Committee in early October of 2024 to ask specifically if Table 9 of CSA S832 meant that force effects did not need to be considered. Their response was as follows:
“The mention in Table 9 is that lightweight suspended T-bar ceilings are not a concern for force effects as they typically do not generate large seismic forces either horizontally or vertically under seismicity levels in Canada. What is important is that the suspension wires need to be firmly secured to the structural support above. Very large ceiling areas may be prone to sway effects if not braced.” - CSA S832 Technical Committee
A good friend and engineer at another local engineering firm also reached out to the same committee in late October 2024, further pressing the issue. They responded:
They do not need a detailed force-related calculation and the prescriptive solution for bracing is deemed adequate. - CSA S832 Technical Committee
Based on the analysis presented in this document, it appears that the CSA S832 Technical Committee’s interpretation of Table 9 may not fully align with the intent of the BCBC. The key difference lies in how load effects are treated. Table 9 of CSA S832 indicates that certain load effects need not be considered, whereas the BCBC explicitly requires that these load effects be accounted for. For this reason, Table 9 of CSA S832 should not be relied upon for projects governed by the BCBC when determining force effects.
g) SEABC Technical Committee Discussion
The Structural Engineers Association of British Columbia (SEABC) briefly addressed this topic in their February 2025 Newsletter. The questioner noted that while CSA S832 includes a prescriptive requirement for lightweight suspended ceilings using 4–12 gauge wires at 12' o/c, BCBC Section 4.1.8.18 indicates that a force-based analytical approach should be used for operational and functional components (OFCs). In response, SEABC encouraged engineers to stay current with the latest standards and apply sound professional judgment when interpreting potential conflicts between CSA S832 and the BCBC. However, they did not explicitly answer the question posed.
3. Project Specs or Statement of Requirements (SOR)
It is worth noting that the previous discussion on applicable codes for T-bar design does not reference the project specifications or the Statement of Requirements (SOR) for a building project. This omission is intentional. When an engineer signs their schedules, they are not certifying compliance with the project specifications or SOR—only with the applicable building codes. Therefore, the engineer is not liable for conformance with the SOR or project specifications in the same way they are for compliance with the building code. This, of course, assumes the engineer has not signed an additional document—such as a modified Schedule S-B—explicitly confirming that all project requirements or the SOR have been met.
However, that is not to say that the project specs or the SOR can be ignored. Doing so would open up your client to enormous liability as well as yourself potentially. Whenever possible or reasonable, the project specs and SOR should be followed. This can be difficult as sometimes the project specs for SOR specify things which are not possible.
4. ASTM E580 Standard Practice for Installation of Metal Ceiling Suspension Systems for Acoustical Tile and Lay-In Panels
ASTM E580 is an American standard that outlines the installation requirements for T-bar ceilings based on seismic zone classifications. Depending on the seismic design category, different installation criteria apply, including:
Design Category C: Regular-duty tees are permitted, wall moldings must be at least 7/8" wide, and vertical posts are required in rooms larger than 144 sq. ft.
Design Categories D–F: Heavy-duty tees are required, wall moldings must be at least 2" wide, and vertical posts must be installed in rooms exceeding 1,000 sq. ft.
Additional requirements—such as wire placement within 8" of all main and cross tee ends (even where riveted) and measures to prevent tee spreading—are also specified.
Some of these requirements are further detailed in our guide to ceiling design for different areas. However, I strongly recommend that any T-bar engineer read the full ASTM E580 standard. It is relatively short but contains critical information essential for proper ceiling design and installation.
a) When the Requirements of ASTM E580 Apply
From the above analysis, it can be seen that the requirements of ASTM E580 are likely NOT brought into the BCBC via CSA S832.
With that said, the requirements of E580 are founded in best practice and based on an analysis of several past earthquakes. Therefore, engineers should only ignore its requirements if they have sound reasons for doing so. The Code of Ethics[4] as required under the Professional Governance Act, S.B.C. 2018, c. 47 still applies which states that registrants must:
Hold paramount the safety, health, and welfare of the public, including the protection of the environment and the promotion of health and safety in the workplace
b) The BCBC as a Reflection of Society’s Current Appetite for Risk
In many ways, the BCBC ultimately reflects society’s collective tolerance for risk. It represents a balance between the economic cost of enhanced safety measures and the consequences of not implementing them. Over time, that balance has shifted. Earlier building codes permitted lower seismic performance levels, but as society has become more affluent and our technical proficiency has advanced, expectations have evolved. With greater resources and a deeper understanding of structural behavior, our tolerance for earthquake-related injuries and damage has decreased. This shift is evident in the increasingly stringent seismic provisions found in the BCBC.
Currently, the BCBC does not appear to directly adopt ASTM E580, as discussed above. As a result, T-bar ceilings with tiles weighing less than 2 psf are not required to conform to ASTM E580. Expecting engineers to follow E580 in all cases would impose an unreasonable burden—there would be no end to how much stronger steel beams should be, how much additional load guardrails should resist, and so forth.
For this reason, it appears that engineers in BC are neither legally (nor ethically) obligated to follow all the requirements of ASTM E580 unless explicitly required by the BCBC.
That said, this could change in future editions of the BCBC. A new version could reference an updated CSA S832, potentially removing the ceiling exemption from Table 9, or it could directly adopt ASTM E580 as a requirement.
5. Loads
From the above discussion, it has been clearly established that T-bar ceilings must be designed to withstand seismic loads as defined in the BCBC, as outlined below. This requirement applies regardless of the prescriptive methods outlined in ASTM E580, any exemptions specified in CSA S832, or even statements from the S832 code committee indicating that ceilings do not need to be designed for seismic loads.
Figure 1: Formula for Seismic Forces for Elements and Components of Buildings (BCBC 2024)
T-bar Requirements
Below, we outline the general requirements for T-bar ceilings in British Columbia. These requirements are currently followed by Thornfield Consulting and by several local engineering firms we collaborated with during this T-bar research.
a) Ceilings less than 144 sf
Per ASTM E580, ceilings less than 144 sf are exempt from the standard. This is presumably because the tees are strong enough to transfer the loads out to the walls.
While ceilings less than 144 sf still must be designed to the loads of the BCBC, a check of the tees should indicate that they are adequate to transfer the loads out to the walls without braces.
With regard to wires within 8” of the end of the main and cross tees, this is a requirement at the terminal end of non-riveted tees to prevent the tees from falling down in an earthquake.
b) General requirements for ceilings greater than 144 sf
The following general requirements apply:
Two sides of the ceiling must be riveted
All main and cross tees must have a wire within 8” of the end of the tee.
Even where the ends are riveted
Cross tees can be supported on a sloping 20 ga wire
A min 3/8” gap to the wall is required
A few of these requirements differ from ASTM E580 (see reasons for this in sections above).
They are as follows:
Clips or spacer bars at the ends of tees are not always required to prevent spreading, except on post-disaster projects. This is because ASTM E580 does not apply to ceilings weighing less than 2 psf, and the support wires already prevent the tees from falling. While clips and spacer bars do help reduce the risk of progressive ceiling collapse, their omission appears to have been considered acceptable by the authors of the BCBC. That said, using clips remains good practice and may still be preferred by the project owner.
A 2″ wall molding or clip isn’t typically required. The 7/8″ gap specified in ASTM E580 may exceed the wall deformation expected at ceiling level during an earthquake. For this reason, a 3/8″ gap is used instead, which provides sufficient clearance while maintaining alignment and finish quality. In addition, 2″ wall moldings are often difficult to source and can noticeably alter the ceiling’s aesthetic, making the smaller molding both practical and visually preferable.
Where the project specs of SOR mandate following ASTM E580, we would issue drawings in complete conformance with sections D-F of E580.
c) Requirements specific to ceilings more than 144 sf but less than 1000 sf
While the lower mainland likely falls within Zones D-F, we allow regular duty tees in this zone. However, when regular duty tees are used, seismic posts must be installed on a 12x12 grid once the room exceeds 144 sf.
This is for a few reasons.
Zone D-F must use heavy duty mains per ASTM E580, however this is along with a 1000 sf area not needing braces. Since we require braces after 144 sf for regular duty tees, this seems like a reasonable trade off.
As discussed above, the prescriptive requirements of ASTM E580 do not apply to projects in BC.
We still design the posts for the forces which they will experience.
If heavy duty tees are used, no posts are required for areas less than 1000 sf.
d) Requirements specific to ceilings more than 1000 sf but less than 2500 sf
If heavy duty tees are used, posts must be installed on a 12×12 for areas greater than 1,000 sf. It is NOT one post every 1,000 sf. Again, if possible, evaluate the tees to ensure they indeed have the strength to transfer the seismic forces to the exterior walls without any braces.
e) Requirements specific to ceilings greater than 2500 sf
Ceilings greater than 2500 sf must have a seismic separation joint.
Conclusion
At Thornfield, we view these standards not as obstacles but as tools for building safer, more resilient spaces. Conversations like this one are how our industry continues to evolve.
This topic touches on an area of ongoing interpretation within our industry, and I’d value hearing how others are approaching it. If you’ve encountered similar questions regarding the interaction between the BCBC, CSA S832, and ASTM E580, I’d welcome your feedback or perspective. Open discussion on these details helps strengthen our collective understanding and improve how we apply these standards in practice. And if you disagree with any part of this analysis, I’d genuinely appreciate hearing your reasoning or suggested corrections. It’s also worth noting that future revisions to the BCBC could change or even render parts of this analysis moot, so continued dialogue and awareness of code updates remain essential.
P.S. If you’re wondering what the point of this very long post is, it’s partly because we’d like to see more clarity on this topic in the NBCC and BCBC. Clearer direction would help engineers understand exactly what’s expected when it comes to T-bar designs and reviews. We’ve spoken with several other engineering firms, and the same questions keep coming up. This article is an effort to shed some light on the issue and maybe even help get a reference to ASTM E580 added to the BCBC.
Footnotes
[3] This clause sounds ambiguous. But as is discussed in section 3 (f), the CSA S832 Technical Committee has on two separate occasions confirmed that that clause intends to remove the requirement to follow force effects. Conceivably, this also means that the reference standards, which help mitigate force effects, are not required.
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