A Fire at Notre-Dame de Paris: A Look at the Wood-framed Historic Landmark, the Mass Timber Movement, and Modern Building Codes - AKF Group LLC
←
→
Page content transcription
If your browser does not render page correctly, please read the page content below
A Fire at Notre-Dame de Paris:
A Look at the Wood-framed Historic Landmark, the Mass Timber
Movement, and Modern Building Codes
The recent fire at the iconic Notre-Dame de Paris cathedral left many people around the world feeling
a sense of loss that’s not commonly felt for inanimate architecture. Although there was no loss of life,
the pain and sadness etched on the faces of Parisians watching the blaze emphasized the significance
of the building. The cathedral is a religious, historical, and architectural landmark that’s been brought
to life through 850 years of history. Thus, when a fire ravages a building such as Notre-Dame, the
damage leaves a wound in the fabric of our history.
Unfortunately, catastrophic fires are also a part of our history. In over 850-years since Notre-Dame was
built, construction methods and building codes have evolved to better protect buildings from fire.
Advancements in fire science have also given the design and construction industry a better
understanding of how timber structures like Notre-Dame perform in fire conditions. These
advancements, coupled with rising steel costs and sustainability benefits, have led to a recent resurgence
in the use of one of the world’s earliest building materials.
In the months before the fire at Notre-Dame, numerous headlines heralded examples of mass timber at
the heart of high-profile projects across the globe. An article on Bloomberg.com proclaimed,
“Skyscrapers Made of Wood Are Making a Comeback,” highlighting the plan by Alphabet Inc.
(Google’s parent company) to use mass timber to build a new mixed-use community in Toronto.1 A
column in The New York Times noted, “builders are choosing timber for offices, apartments and campus
buildings, rather than the concrete and steel that dominated construction for decades.” 2 Even the Tokyo
2020 Summer Olympic and Paralympic Games are set to showcase 70,000 cubic feet of wood sourced
from across Japan at the Kengo Kuma-designed National Stadium.3
This resurgence in mass timber is made possible by numerous advancements in building codes and
industry practices. By better understanding the capabilities of mass timber construction, modern building
codes are able to specify additional safety measures to maintain the fire safety of mass timber buildings.
As a result, Notre-Dame is not only unique because of its historical significance, it’s also unique because
a cathedral built under modern building codes would look significantly different than the historic
landmark.
1
Skerritt, J. (2019, February 8). Skyscrapers made of wood are making a comeback. Retrieved from Bloomberg:
https://www.bloomberg.com/news/articles/2019-02-08/skyscrapers-made-of-timber-make-comeback-nudged-
by-google-unit
2
Hughes, C. (2019, January 1). Log Cabins? No, These Wooden Buildings Are High-Rises. Retrieved from The
New York Times: https://www.nytimes.com/2019/01/01/business/timber-wood-construction-real-estate.html
3
Hilburg, J. (2019, January 16). Kengo Kuma is crafting a timber temple to sports for the 2020 Olympics.
Retrieved from ArchitectsNewspaper: https://archpaper.com/2019/01/kengo-kuma-2020-tokyo-olympic-
national-stadium/#gallery-0-slide-0
| 99 Bedford Street, 2nd Floor, Boston, MA 02111 | T: 617.737.1111 | akfgroup.com |
The Construction of Notre-Dame
Construction of Notre-Dame cathedral began in 1163 and continued until the mid-1200s. The
cathedral has undergone several reconstructions and renovations up until the current renovations that
were underway when the recent fire started. The majority of the outer structure of the building is
constructed of stone, while the framing for the roof and iconic spire consisted of solid wood beams. The
wood framing contained so many beams that the structure was nicknamed “the forest”. The roof framing
supported a lead roof weighing approximately 210 metric tons.4, 5, 6
The footprint of the cathedral is approximately 67,000 SF. The building was equipped with a fire alarm
system, which activated during the fire. While the cathedral did not have a sprinkler system, the activation
of the fire alarm system alerted the occupants of the building and all were able to evacuate safely.6, 7, 8
Modern Code Requirements
The International Building Code (IBC) is published by the International Code Council and used as a
model code throughout the United States and other countries around the world.9 The IBC contains
design and construction requirements for various types of buildings, including places of religious
worship. The latest edition of the IBC is the 2018 edition; however, the 2021 edition is under
development.10
While in general, there are specific exemptions from certain code requirements for religious buildings,
such buildings must still comply with several general construction requirements. For example, based on
the construction materials used for Notre-Dame cathedral and the lack of an automatic sprinkler system
in the building, a similar building constructed under the IBC would be limited to 15,000 SF. Notre-
Dame cathedral is over four times that size. In addition, the IBC requires sprinklers to be installed in
places of religious worship that exceed 12,000 SF. Therefore, a sprinkler system would have been
required in Notre-Dame had it been built under the current edition of the IBC. 11
4
Notre-Dame De Paris. (n.d.). Construction history. Retrieved from Notre-Dame De Paris:
http://www.notredamedeparis.fr/en/la-cathedrale/histoire/historique-de-la-construction/
5
Notre-Dame De Paris. (n.d.). The Frame. Retrieved from Notre-Dame De Paris:
http://www.notredamedeparis.fr/en/la-cathedrale/architecture/la-charpente/
6
Irfan, U. (2019, April 17). Why the Notre Dame fire was so destructive, according to fire experts. Retrieved
from Vox: https://www.vox.com/2019/4/16/18312072/notre-dame-cathedral-fire
7
Ries, B., Rocha, V., Picheta, R., McKirdy, E., Yeung, J., Mezzafiore, G., & Murphy, P. P. (2019, April 17). Fire
at Notre Dame Cathedral. Retrieved from CNN: https://www.cnn.com/world/live-news/notre-dame-
fire/h_73a6f83bc82d99151da5a7b2208f94f3
8
The Editors of Encyclopedia Britannica. (2019, April 16). Notre-Dame de Paris. Retrieved from Encyclopedia
Britannica: https://www.britannica.com/topic/Notre-Dame-de-Paris
9
International Code Council. (2019). United States Usage of the I-Codes. Retrieved from International Code
Council: https://www.iccsafe.org/about-icc/overview/international-code-adoptions/
10
International Code Council. (2019). Overview of the International Building Code (IBC). Retrieved from
International Code Council: https://www.iccsafe.org/codes-tech-support/codes/2018-i-codes/ibc/
11
International Code Council. (2017). 2018 International Building Code. Country Club Hills: International Code
Council.
| 99 Bedford Street, 2nd Floor, Boston, MA 02111 | T: 617.737.1111 | akfgroup.com |
While there are specific exemptions in the IBC that allow religious buildings to be unlimited in area,
there are several safety measures required to use such exemptions (Figure 1). Most notably, regardless
of the type of construction materials, the building would need to be fully sprinklered under the IBC in
order to take advantage of the unlimited area allowance.11
Some Combustible
Noncombustible
Building Elements
Building (Type II)
(Type III or IV)
Maximum of Maximum of
one story one story
Fully Fully
sprinklered sprinklered
building building
Cannot Cannot
contain a contain a
stage stage
60' of open 60' of open
space around space around
the building the building
Exits at or near
grade level
Figure 1 - IBC Exemptions for an Unlimited Area Religious Building11
In addition to the basic size and construction requirements for buildings similar to Notre-Dame, current
building codes require additional safety features such as emergency lighting, exit signage, and minimum
number and size of exits. The IBC also places a significant emphasis on automatic sprinkler systems in
modern buildings. Based on a report from the National Fire Protection Association (NFPA), in structure
fires in the United States between 2010 and 2014, automatic sprinklers were able to control 96% of
the fires in which they activated. Automatic sprinkler systems have shown significant effectiveness in
limiting the property damage, loss of life, and injuries sustained during a building fire.12 As a result,
such systems have become a staple in modern building design.
12
Ahrens, M. (2017). U.S. Experience with Sprinklers. Quincy: National Fire Protection Association. Retrieved
from https://www.nfpa.org/-/media/Files/News-and-Research/Fire-statistics-and-
reports/Suppression/ossprinklers.pdf
| 99 Bedford Street, 2nd Floor, Boston, MA 02111 | T: 617.737.1111 | akfgroup.com |
The Future of Mass Timber
Timber construction similar to that used in Notre-Dame is still permitted in modern buildings (designated
as heavy timber construction). Designers are also starting to turn to even larger timber members, referred
to as mass timber. While steel and concrete have historically been standard building materials for large-
scale buildings, mass timber has started to emerge as a more favorable option. Due to the rising cost
of steel, a lower carbon footprint, and faster construction schedule, mass timber has become
increasingly popular in modern buildings.1 However, modern-day mass timber is distinctly different than
traditional heavy timber.
The IBC prescribes minimum dimensions for heavy timber members, to ensure the members have a
certain amount of inherent fire resistance (Figure 2).11 Although wood is combustible, larger timber
members have an inherent fire resistance due to the char layer that forms on the member when
exposed to fire. As the outer layer of a wood member degrades during a fire, that wood is converted
into a layer of char. This char layer insulates the rest of the wood and slows the degradation of the
member.13
Figure 2 - 2018 IBC Heavy Timber Dimensional Requirements11
As a result of this inherent fire resistances, members with the minimum dimensions specified
in Figure 2 are recognized by the IBC as generally equivalent to 1-hour fire-resistance rated
construction.11 However, even if the wood structure in Notre-Dame was consistent with the
dimensions in Figure 2, the building is still over four times larger than the current IBC allows.
13
White, R. H. (2016). Analytical Methods for Determining Fire Resistance of Timber Members. In SFPE
Handbook of Fire Protection Engineering (pp. 1979-2011). Springer.
| 99 Bedford Street, 2nd Floor, Boston, MA 02111 | T: 617.737.1111 | akfgroup.com |
Modern construction techniques have introduced composite mass timber members such as cross-
laminated timber (CLT). CLT consists of at least three layers of solid-sawn or structural composite lumber
that are bonded by structural adhesive. CLT and other composite mass timber members are also
considered heavy timber construction and can be used under the IBC.11
The development of CLT and other composite timber members has led to the ability to construct larger
structural members out of wood. As a result of the insulating properties of char layers, these mass timber
members can provide greater fire resistance and structural capacity. Coupling larger timber members
with noncombustible components such as gypsum and concrete can achieve an even greater level of
fire-resistance than exposed timber members.
As a result of the advancements in timber construction and recent fire testing of modern timber
assemblies, approved changes to the 2021 IBC will allow larger timber structures than previous editions.
The existing timber construction classification (Type IV) will remain unchanged, but the 2021 IBC will
introduce three new timber construction types, each with an increased level of fire-resistance and
decreased amount of exposed wood (Figure 3). Type IV-C construction is considered similar to
the existing heavy timber construction classification; however, a greater level of fire-resistance is
provided by using larger timber members. Type IV-B construction has similar fire-resistance to Type IV-
C construction; however, less exposed wood is permitted in Type IV-B construction. Finally Type IV-A
construction provides the greatest level of fire-resistance and does not allow any exposed timber. 15
Figure 3 - 2021 IBC Timber Construction Classifications
15
International Code Council. (2018). 2018 Group A Proposed Changes to the I-Codes Columbus Committee
Action Hearings. Columbus: International Code Council. Retrieved from http://media.iccsafe.org/codes/2018-
2019/GroupA/CAH/IBC-G.pdf
| 99 Bedford Street, 2nd Floor, Boston, MA 02111 | T: 617.737.1111 | akfgroup.com |
The ability to create larger timber members with greater fire-resistance now allows timber buildings to
be larger than previously permitted by the IBC. Advancements in construction techniques and fire science
have given the construction industry a better understanding of the allowances and limitations of wood
construction. These advancements now allow designers to safely use wood construction in larger
buildings.
Conclusion
A modern Notre-Dame would have several noticeable differences from the historic landmark. Under
today’s building codes, a religious building of similar size requires either an automatic sprinkler system,
noncombustible construction, larger timber members, and/or less exposed wood. Such safety measures
are now required to reduce the fire hazard in modern buildings. While Notre-Dame and other historic
buildings are not built to modern codes, many historic buildings are retrofitted to include modern fire
safety technology (including Notre-Dame). While the damage to the structure is tragic, the fire could
have been much more tragic had occupants not been given the advanced warning provided by the fire
alarm system.
Ultimately, it isn’t fair to compare an 850-year old structure to the requirements and advancements of
modern building codes. However, the building can be used to reflect on how far such codes have come.
Since the construction of Notre-Dame, architects and engineers have continued to push the boundaries
of construction. With today’s advancements in construction techniques, modern buildings are able to
harness the benefits of wood construction, while still achieving fire safety. It’s buildings like Notre-Dame
that have helped to advance the world’s collective understanding of what can be achieved through
architecture and engineering. As a result, buildings have continued to be built stronger and safer than
those before.
About the Author:
Mariah Seaboldt is a registered fire protection engineer in the state of Massachusetts.
She has a bachelor’s degree in civil engineering and a master’s degree in fire
protection engineering from Worcester Polytechnic Institute. Mariah is part of the
Architectural Code Consulting team at AKF Group in Boston, MA, where she
specializes in building, fire, life safety, and accessibility code consulting for both
existing building renovations and new construction projects.
About AKF Group:
AKF delivers innovative solutions and leadership to optimize the built environment and redefine the
edge of what’s possible. With more than 500 dedicated team members and eleven offices
throughout North America, AKF provides a robust offering of Integrated Services, including:
Mechanical, Electrical, Plumbing, Fire and Life Safety Engineering, Architectural Code Consulting,
BIM Management, Building Controls, Central Utilities, Cogeneration, Commissioning, Critical
Systems, Energy + Performance, IT/AV/Security, Lighting Design, Special Inspections, and Vibration
Analysis & Testing.
For additional information about AKF, please visit www.akfgroup.com.
| 99 Bedford Street, 2nd Floor, Boston, MA 02111 | T: 617.737.1111 | akfgroup.com |
You can also read
