Adaptation of Low-Slope Roof Assemblies Against Projected Climate Severities: Evaluation of a New Standard

by the manufacturer. Low-slope roof assemblies,
excluding protected roof membrane assemblies,
are now required to resist the project-specific
wind uplift loads of three different zones of a roof
area: the field, edges, and corners. To meet this
requirement, each of the project team members,
including designers, manufacturers, and
installers, must play a pivotal role. However, there
have unfortunately been cases in which team
members have not adequately carried out their
responsibilities, and a combination of errors and/
or omissions have led to failures.
Addressing the project-specific challenges
related to the wind load is a crucial starting point in
achieving long-term durability of roof assemblies,
but it is not the only concern. The other main
challenge is to design roof assemblies that resist and
manage precipitation. To address that challenge,
project teams must take into account the NBCC2
requirements for sizing drains and rainwater leaders.
In addition, there are several qualitative measures
followed in the industry that are either industry
best practices or standards, including standards
published by roofing contractors’ associations,
for example Roofing Practices Manual of Roofing
Contractor’s Association of British Columbia.4
With the changing climate and anticipated
climate severities, there is a need to further
enhance the above mentioned requirements for
roof assemblies to resist increased wind load, to
control and manage increased precipitation, and
to counter increase in temperature from having
an impact on the durability. To meet this need,
NRC in collaboration with the SIGDERS committee
has developed Performance Requirements for
Climate Resilience of Low Slope Membrane
Roofing Systems (CSA A123.26),5 which addresses
the severities related to wind and rain.
THE PERFECT STORM—
A CASE STUDY
On December 14, 2021, a six-story multi-unit
residential building under construction in the
Adaptation of Low-Slope Roof
Assemblies Against Projected
Climate Severities: Evaluation
of a New Standard
Feature
By Sathya Ramachandran, Architect, OAA,
MRAIC, BArch, MASc, and Bruno Bernard
This paper was presented at the 2024 IIBEC/
OBEC BES.
Greater Toronto Area reported roof damage
caused by a strong wind event (Fig. 1).
The fully adhered thermoplastic polyolefin
(TPO) roof assembly over concrete deck
with a layer of vapor retarder, two layers of
polyisocyanurate insulation, and a layer of
high density polyisocyanurate coverboard had
experienced wind uplift damages due to high
wind conditions that reached up to 96.3 km/h
(59.8 mph), as recorded by the nearby weather
stations. The damage covered approximately
15 percent of the roof assembly, across four
different locations. At first glance, the roof
assembly failure appeared to be due to heavy
wind conditions experienced at the time of
the event that may have exceeded wind uplift
design parameters. However, subsequent
review determined that the wind conditions
were found to fall within the expected wind load
range for the site. The project experienced a
series of missteps leading to the failure event,
all potentially contributing to create a ‘perfect
storm’ scenario. The potential contributing
factors include: failure by the designer to specify
project-specific wind uplift values in the design
specification; alternative questionable methods
of compliance employed by the manufacturer;
and poor material handling, poor workmanship,
and poor quality control by the contractors
during construction (Fig. 2, 3, and 4). While
the primary cause of failure can be attributed
to one or more of the above missteps, this roof
failure incident provided some insights that are
valuable lessons learned. For further discussion
of the issues noted herein, refer to the article by
Ramachandran et al., “Wind Uplift Failure of a
Roof Assembly: The Perfect Storm.”6
MEETING CODE REQUIREMENTS
FOR WIND UPLIFT
To satisfy code requirements for wind uplift,
designers must first calculate and/or use
the available online calculator to determine
Interface articles may cite trade, brand,
or product names to specify or describe
adequately materials, experimental
procedures, and/or equipment. In no
case does such identification imply
recommendation or endorsement by
the International Institute of Building
Enclosure Consultants (IIBEC).
IN 1994, THE National Research Council
of Canada (NRCC) led the way to form a
consortium-based research and development
study group, the Special Interest Group
for Dynamic Evaluation of Roofing System
(SIGDERS), which includes representatives
of manufacturers, contractor’s associations,
testing laboratories, homeowners, and
insurance companies. The group’s research
led to the development of the CSA A123.21,
Standard Test Method for the Dynamic Wind
Uplift Resistance of Membrane- Roofing
Systems,1 which was first published in 2004 and
subsequently revised in 2010, 2014, and 2020.
Referenced in the National Building Code of
Canada (NBCC)2 since 2015 edition and adopted
by the provincial codes, including the Ontario
Building Code (OBC),3 CSA A123.211 specifies
the primary means of assessing a roofing
system’s resistance to counteract calculated
wind loads and has become a pivotal point in
the development of roofing specifications.
With the codification of CSA A123.21,1 the
design and construction of roof assemblies for
buildings built in Canada are no longer a simple
composition of layers of roof components,
relying on the proprietary design of the system
©2025 International Institute of Building Enclosure 18 • IIBEC Interface Consultants (IIBEC) July/August 2025
as offered by the manufacturer is to be used.
Additionally, crews must pay attention to
details at the time of construction, such as
temporary seals at perimeter scuppers and
openings, and along end of workday assembly
terminations, to avoid loss of integrity of
the roof assembly due to inclement weather
including extreme weather conditions that
may occur during installation. Quality control
measures by the general contractor and roofing
trades are essential to verify that materials and
components are properly installed. A general
conformance review by the designer and a
qualified consultant as required is imperative
during construction.
CALCULATING
PROJECT-SPECIFIC WIND
UPLIFT REQUIREMENTS
The project-specific wind uplift load values
are calculated based on load-resistance-factor
design (LRFD) with inputs including the
Figure 1. Failed roof assembly after heavy wind conditions. Figure 2. Poor installation practices observed and corrected.
the project-specific wind uplift values and
include them in the project specifications. In
addition, it is advisable for the designer to
specify a requirement for the contractor to
submit reports issued by third-party testing
laboratories to confirm that the procured roof
assemblies are rated to exceed the required
project-specific wind uplift values. If the
designer chooses to include basis-of-design
roof assemblies in the specification, the
designer may choose to research and/or work
with manufacturers to identify rated roof
assemblies that meet the project-specific
requirements. Some manufacturers and
third-party testing laboratories have posted
online the roof assembly resistance reports
with their ratings that can help the designer
identify appropriate roof assemblies. NRC
is in the process of developing a portal
with database of tested roof assemblies
from various manufacturers to provide a
centralized resource. At the time of the roof
assembly procurement, the roofing contractor
can work with manufacturers to identify
a roof assembly that is rated to resist the
project-specific wind uplift load requirements
of all zones at each of the roof areas of the
building, and present as a substitution
request for designer’s approval.
While the selection of a rated roof assembly
is an important step, the general contractor
and roofing trade must take responsibility for
good workmanship and the correct installation
of the selected system. It is critical to follow
the manufacturer’s instructions for the
tested assembly, including the use of proper
spacing, patterns, and installation timing
for each of the components. Materials must
be properly stored, and proper precautions
taken at the time of installation to ensure
the effective functioning of the components.
For installation of assemblies during winter,
those components that are affected by cold
weather conditions, a winter-grade product
Figure 3. Exploratory opening investigation conducted post failure. Figure 4. Removal of failed roof for repair.
July/August 2025 IIBEC Interface • 19
geographical location, terrain of the project
site, openings in the building, height of the
building, size of the roof area, and height of the
parapet. NRCC has developed and published
an online tool, Wind-RCI,7 that can calculate
these values based on the user’s project-specific
input. This tool can be used to calculate the
required size or width and corresponding wind
uplift resistance values for field, perimeter, and
corner zones of each roof area, as required, based
on the building information and site location
characteristics. The online tool has limitations:
it is not applicable to buildings exceeding 45 m
(150 ft) in height, and it should be cautiously
used for buildings located in dense metropolitan
locations where microclimatic site conditions
may influence load values in ways not captured
by the tool’s calculations, for instance locations
that experience wind tunnel effects in downtown
core of major cities. It is important to note
that, as is the case with any tool, it is the user’s
responsibility to verify the values generated by
Wind-RCI.7
THIRD-PARTY LABORATORY
TESTING TO RATE ROOF
ASSEMBLIES
CSA A123.211 is a rigorous test method that
simulates the effects of wind pressure on a
roof assembly specimen. The test method is
straightforward: a complete 3.7×7.3 m (12×24 ft)
specimen composed of the layers of the tested
roof assembly, which may include a thermal
barrier, a vapor retarder, insulation layers, cover
board, and a roofing membrane system, is
installed on a deck, usually of corrugated steel,
attached to a specially designed test rig (Fig. 5).
An airtight chamber is then placed on the
specimen to ensure airtightness at the junction
where the chamber meets the bench (Fig. 6).
An air suction system and computer-controlled
shutters modulate the pressure and duration of
the vacuum created in the chamber, simulating
the pressure effects experienced by roofs during
their service life.
The test procedure consists of consecutive load
cycles, in predetermined sequences, divided
into five levels and two methods, and it is carried
out to assess maximum stress until an evident
roof failure is observed. The test may last up to
10 hours, depending on the performance of the
assembly, during which time the test pressures
and behavior of the roof specimen are constantly
monitored. At the end of the test period, an
investigation is carried out to understand the
dynamics of the rupture, if any, and to assess
possible improvement options to enhance the
performance of the assembly (Fig. 7 and 8).
CHALLENGES EXPERIENCED
IN MEETING THE WIND UPLIFT
REQUIREMENTS
An issue experienced in the industry is for
the designers to transfer the responsibility
of determining wind uplift requirements to
roofing contractors and/or manufacturers
by referencing the building code in the
specifications, rather than specifying the
required project-specific wind uplift values.
However, it is prudent for the designers to be
informed of the code requirements and either
verify the project-specific wind uplift values
themselves or engage qualified professionals
to provide verified values. Doing so eliminates
ambiguity, upholds the standard of care, reduces
risk and liability, and prevents cutting corners.
In June 2018, the Canadian Roofing Contractors
Association issued an advisory bulletin8 to
communicate the responsibility of confirming
project specific wind uplift loads lies with the
designer and not the roofing contractor, and the
reasoning for this design responsibility has been
dissected at length by Klassen in a 2021 article.9
In addition to verifying the project-specific
wind uplift values, the designer must obtain test
reports supplied by a third-party testing facility
that uses apparatus properly calibrated as per the
CSA A123.211 protocol, and verify that the tested
rating of the proposed assembly meets the
project-specific wind uplift load requirements
for each of the roof areas for all zones. It is
also important that the designer understands
whether the manufacturer proposes to meet the
requirements by using the extrapolation method
set forth in the Wind Design Standard Practice
for Roofing Assemblies (ANSI/SPRI WD-1).10
ANSI/SPRI WD-1 that provides calculation
means to enhance securement. If that is the
manufacturer’s intention, the manufacturer
should provide the details of calculation and any
other information that the designer may require
to assess the risk. The designer should assess
the suitability of the extrapolation method by
verifying the calculation and taking into account
the mode of failure experienced during the
original test. While the extrapolation method
may be appropriate for mechanically attached
roofing systems (MARS), it is not suitable in all
circumstances for fully adhered roofing systems
or partially adhered roofing systems (PARS). For
instance, if a roof assembly’s mode of failure is
due to cohesive failure of one of the layers of a
roof assembly at its ultimate capacity, improving
the adhesion of the layers by reducing the
spacing of the adhesives (which is a common
approach for extrapolation) will not improve
the overall performance of the roof assembly.
Regardless of the amount and spacing of the
adhesive, the roof assembly will experience
cohesive failure of the layer at its ultimate
capacity before reaching the project-specific
wind uplift resistance values. The designer may
specifically note that extrapolation methods of
compliance and the use of noncalibrated testing
facilities are unacceptable. The safest approach
is to ensure that the rating of the proposed roof
system is confirmed through third-party testing
and meets or exceeds project-specific wind uplift
resistance values for all roof zones.
Figure 5. Installation of a roof assembly specimen. Figure 6. Airtight chamber mounted over the roof specimen.
20 • IIBEC Interface July/August 2025
Canada’s requirements. The objective of CSA
A123.265 is to outline specific quantitative
and qualitative requirements in the selection
and detailing of low-slope membrane roofing
systems to resist the impacts of anticipated
climate severities. The standard addresses
two main elements of the anticipated climate
severities: wind and rain. Regarding wind, the
pivotal requirement for the roofing system’s
long-term performance is resistance to wind
loads, which includes the determination of
project-specific wind uplift loads and selection
of an appropriate assembly that can resist
the determined load. Additional qualitative
requirements in the standard are in line with
the determined wind uplift loads. Regarding
rain, the standard has design requirements
for the roofing system to collect, manage, and
dispose of anticipated additional rainwater due
to climate severities, as well as several qualitative
requirements.
CSA A123.265 provides three performance
levels for low-slope membrane roofing systems:
Bronze, Silver, and Gold. The Bronze level
represents the current requirements included in
the NBCC2 and National Energy Code of Canada
for Buildings (NECB),12 which do not take into
account anticipated future climate severities.
The Silver and Gold levels include provisions
to counter the impacts of anticipated climate
severities and the level of resilience required for
the type of building and use.
NRCC has developed an online tool,
Climate-RCI,13 based on the information from
Environment and Climate Change Canada. This
tool allows users to input a building’s location in
Canada and select a magnitude of global warming
(0.5°C to 3.5°C [0.9 to 6.3F]). Based on these
inputs, the tool classifies the severity of wind,
rain, and temperature for the building’s location
Figure 7. Destructive testing upon completion of a test to evaluate the
mode of failure. Figure 8. Mode of failure observed upon completion of testing.
While it is critical that the designer exercise
prudence during the design stage and
verification at the procurement stage, these
precautions will not be sufficient if the installers
on site are not informed of or do not follow the
same configurations of assembly securements
that were used for the tested specimen (i.e., if
they do not use the same attachment methods
for the roof assembly layers). To ensure that
the constructed roof assembly meets the code
requirements, it is imperative that the project
includes standard of acceptance or mock-up
reviews, general conformance reviews, and
quality assurance inspections.
The wind uplift loads at the corner are typically
higher than at the edge and field conditions.
Therefore, there is technically an option to install
a roof assembly at the field and edge conditions
that is rated lower than the assembly for the
corner conditions. Choosing to install varied
assemblies at the field, edge, and corner will
have cost benefits, particularly on larger roofs.
Such installations with varying performance
ratings should be carefully evaluated on a
case-by-case basis to verify that the variation will
not have a performance impact at the transitions
between the assembly types. Certain conditions
may apply in projects that allow different
roof assemblies for each of the zones; these
conditions include maintaining the same roof
composition for all zones in terms of materials,
positioning of layers, and thickness of layers;
maintaining a consistent thickness for all the
assemblies; or using roof area dividers where
variations are distinct.
PROJECTED CLIMATE
SEVERITIES
In addition to meeting current code
requirements, designers and contractors also
need to understand that further enhancements
to the way roof assemblies are constructed
for long term durability may be necessary to
prepare for climate-change-driven events such
as intense windstorms, heavy precipitation,
and increased temperature. With the Earth’s
current surface temperature already reaching
1.5°C (2.7F) warmer than pre-industrial levels,
the occurrence of severe climate-related
conditions is anticipated immediately and
throughout the course of the service lives of
existing and to-be-built building stocks. Among
building envelope components, roofs tend to
be especially vulnerable to climate-related risks
due to their exposure to increase and variation
in temperature, windstorms causing wind uplift
failures, and extended water and snow retention.
According to Engineers Canada,11
Engineers have a significant role to play
in addressing climate change issues and
incorporating them into engineering
practice in Canada… Engineers, under
their professional code of ethics, play a
fundamental role in ensuring construction
and operation are continuously adapted
to the impacts of climate change to ensure
public safety.
SCOPE AND APPLICABILITY
OF CSA A123.26
To support the design community in countering
the anticipated effects of climate severities, the
Task Group on Climate Resilience of Low Slope
Membrane Roofing Systems developed CSA
A123.265 under the authority of the Technical
Committee on Bituminous Roofing Materials
and the Strategic Steering Committee on
Construction and Civil Infrastructure. The
document was published in 2021 as a national
standard that meets the Standard Council of
July/August 2025 IIBEC Interface • 21
as normal, severe, or extreme. Additionally, the
tool provides quantitative design parameters:
1/50 hourly wind pressure and 1/50 one day rain,
representing a 50-year mean recurrence for wind
and rain, respectively, and anticipated maximum
daily temperature for heat. The tool then requires
the user to select a resiliency index of 1, 2 or
3, wherein the selection of a higher resiliency
index, means the intent to achieve higher roof
resilience. Resiliency index 1 aligns performance
requirements with current provisions of NBCC2
and NECB.12 Resiliency index 3 is defined as
follows: “Roofing systems are fully functional with
required performance for normal and emergency
operations irrespective of the climate conditions.
Damage to contents is minimal in extent and
minor in cost. Resiliency index 2 is for any level
of performance requirement between Resilience
Index 1 and 3. The user should select the resiliency
index based on the expected function of the
building (especially importance category and risk)
and the resiliency required in terms of recovering
from disturbances and adapting to climate
severity. After the resiliency index for the project is
selected, the tool produces a summary of design
parameters for the project, including required roof
performance level, whether Bronze, Silver, or Gold.
When the combination of climate index and
resiliency index identifies a Bronze level roofing
system for the entered inputs, the performance
requirements are the current NBCC2 and NECB12
requirements, and the project-specific wind
uplift values can be determined using Wind-RCI.7
When the roofing system is classified as Silver,
it is assumed that the roof assembly will comply
with the NBCC22 and NECB12 requirements
as well as some additional requirements
specified in CSA A123.26.5 Similarly, in case
of the Gold performance level, the roofing
assembly must meet the Bronze and Silver level
requirements plus additional requirements
specified in CSA A123.26.5 In the event of a
conflict in requirements between the levels,
the requirements of the highest level would
take precedence. Figure 9 illustrates the various
relationships between the climate category and
resiliency index in the selection of the required
performance.
CSA A123.265 is applicable to adhesive
applied roof systems (AARS), partially adhered
roof systems (PARS), and mechanically attached
roof systems (MARS). An AARS involves using
adhesives to bond the roofing layers, mainly
the cover board and insulation, on to lower
layers. A PARS involves using a combination of
adhesive and mechanical fasteners to secure the
roofing system to the substrate. In a MARS, the
roofing system is secured to the substrate with
mechanical fasteners such as screws or nails.
CSA A123.265 does not address the climatic
adaptation requirements for the structural
support (deck) below the roof assembly, which
should be handled through enhancements to the
structural design of the buildings.
RESISTANCE TO WIND
UPLIFT LOADS
Using Climate-RCI,13 by inputting the project
location and global warming magnitude,
designers can determine the qualitative severity
of the anticipated future wind conditions
as either normal, severe or extreme and a
quantitative 1/50 hourly wind pressure. For
instance, the severity and wind uplift pressure
value for a project located in Toronto (City Hall)
with a global warming magnitude of 2°C (3.6F)
is ‘severe’ and 0.46 kPa (9.67 psf) respectively.
For the same location and a global warming
magnitude of 3.5°C the severity is ‘extreme’ and
wind pressure value is 0.50 kPa (10 psf). The
wind pressure value is then used to calculate
the factored wind loads either following the
procedure outlined in section 4.1.7 of NBCC2 or
using Wind-RCI.7 It is to note that the required
performance level for the roof, whether Bronze,
Silver or Gold may vary depending on the
selection of Resiliency Index.
Table 1 presents the wind uplift pressures
determined for a hypothetical building of
9 m (30 ft) height in Toronto (City Hall), and
its corresponding factored wind uplift loads
Climate Category Resiliency Index 1 Resiliency Index 2 Resiliency Index 3
Normal Bronze Silver Gold
Severe Silver Silver Gold
Extreme Gold Gold Gold
Figure 9. The application of climate category and resiliency index to identify a roofing assembly’s
performance level.
TABLE 1. Wind load determination for Toronto using Climate-RCI,13 Ontario
Global Warming
Magnitude
Climate Severity
for Wind
Wind Pressure
Value
Factored Wind
Uplift Load
Resiliency
Index
Required Performance
Level for Wind
Source: Climate-RCI13 Source: Wind-RCI7 Source: Climate-RCI13
0.5°C Normal 0.44 kPa
Corner -2.6 kPa 1 Bronze
Edge -1.3 kPa 2 Silver
Field -1.0 kPa 3 Gold
2°C Severe 0.46 kPa
Corner -2.7 kPa 1 Silver
Edge -1.4 kPa 2 Silver
Field -1.1 kPa 3 Gold
3.5°C Extreme 0.5 kPa
Corner -2.9 kPa 1 Gold
Edge -1.5 kPa 2 Gold
Field -1.2 kPa 3 Gold
Note: Above values are for a roof with no parapet
22 • IIBEC Interface July/August 2025
and required performance levels for different
resiliency indices.
WIND UPLIFT RESISTANCE AT
CORNERS AND EDGES
The presence of roof parapets can significantly
minimize the effect of wind load at the roof
perimeters, i.e., corners and edges. When
calculating the factored wind uplift loads per
NBCC2 or using Wind-RCI7 to meet current code
(Bronze level), the presence or absence of a
parapet is one of the factors in determining the
project specific requirements. For instance, for the
above Toronto example, the factored wind uplift
loads for the roof assembly with no parapet are
Corner -2.6 kPa; Edge -1.4 kPa; and Field -1.1 kPa.
The same roof with a 1 m (3 ft) parapet will
have reduced factored wind uplift values of
Corner -2.2 kPa, Edge -1.3 kPa, and Field -1.0 kPa.
While the presence of a parapet reduces the wind
uplift loads within the roof area, the wind loads
against the parapet cladding and its components,
particularly the top edge of the parapet, will be
higher and is to be determined. For instance, in
the above scenario, the factored wind loads for
parapet cladding and metal edge components
will be -2.9 kPa in suction for Corner and -1.7 kPa
in suction for Edge, and a positive load of 1.4 kPa
at the face of the parapet.
For the Silver and Gold level roofs, the values
determined are required to be increased by 30%
and 50% respectively if a parapet is not installed.
Table 2 presents the wind uplift values for each
of the performance levels for the above example.
The alternative option of installing a
0.9 m (3 ft) high parapet must be installed as
an extension of the main structural system of
the building and meet the determined wind
uplift loads. Installation of a roof parapet as an
extension of the main structural system poses
challenges in achieving continuity of the air
barrier at the intersection detail between the
exterior wall and roof assemblies. Lack of air
barrier continuity may contribute to wind uplift
failures in addition to the potential condensation
issues within the parapet assembly. Hence, the
roof-to-exterior wall junction detailing at the
base of a roof parapet installed as part of the
main structural system requires special attention
to ensure that the continuity of the air barrier is
maintained.
In addition to the requirement to either
install a 0.9 m (3 ft) high parapet or increase
the performance requirements to counter
the higher wind uplift loads for the roof
perimeters, CSA A123.265 includes a
requirement to reinforce the field membrane
termination using metal bars or plates with a
maximum spacing of 152 mm (6 in.) to provide
secondary protection against membrane
lifting and peeling or pulling away from the
roof perimeter. The required use of metal
components to secure membrane termination
to the structural elements such as metal
decks may cause some thermal bridging
around the fasteners. However, the risk of
wind uplift failures and consequential repair
or replacement of roof assembly trumps the
marginal increase of thermal bridging at the
roof perimeters. Another possible challenge
with the installation of term bars and plates is
the potential inhibition of rainwater drainage.
As an alternative to the requirement to install
the term bar and plates, the standard includes
an option to further increase the wind uplift
loads for the perimeter zones by 30% for
parapets with a height greater than 914 mm
(3 ft) and 50% for parapets with a height lower
than 914 mm (3 ft).
Wind uplift loads are significant at parapets,
particularly at the top edges, which experience
complex wind aerodynamics. Cap flashings,
including cleats and their fasteners, require an
appropriate thickness and attachment spacing
to resist the determined wind uplift load
requirements as that of the roof assembly. The
wind forces on the parapet and cap flashing
are complex and depend on the roof slope,
parapet height, parapet shape, and internal
pressure between the wall and edge metal. The
cap flashings, particularly at the corners, have
a high probability of failure, which can lead to
further failure of the rest of the flashing, other
parapet components, and the membrane of the
roof system. In addition to the requirements
listed in CSA A123.26,5 refer to ANSI/SPRI ES-1,
Wind Design Standard for Edge Systems Used
with Low Slope Roofing Systems,14 for further
guidance. The CSA A123.265 requires that the
membrane flashing be fully adhered on the
vertical upturn of the parapet, and wrapped
over the top edge of the parapet, with fasteners
securing the membrane flashing through cleats
to limit failure.
ROOFTOP ADD-ONS
A critical issue related to the rooftop add-ons
is their resistance to wind uplift loads. With
regard to the design of rooftop add-ons, CSA
A123.265 requires that add-on components
and their anchorages meet the wind uplift
load requirements for the roof assembly. For
vegetated roof assemblies, CSA A123.265
references CSA A123.24, Standard Test Method
for Wind Resistance of Modular Vegetated Roof
Assembly,15 to determine the project-specific
wind uplift loads and airflow conditions for
either the built-in-place vegetated systems or
the modular vegetated system. The intent of
the test is to evaluate the overturning and/or
displacement of the vegetated roof components
mounted on the roof assembly samples when
wind uplift loads are applied.
When there are exterior-mounted rooftop
units such as mechanical, electrical, and
communications equipment, air intakes, vent
stacks, guywires, or solar panels, the attachments
for the rooftop units and the supporting frames
can be insufficient or missing. When the wind
TABLE 2. Wind load determination for Toronto (City Hall), Ontario
Location-specific wind loads per Wind-RCI7 Location-specific wind loads per Wind-RCI7 and Climate-
RCI13 with increase of 30% for Silver and 50% for Gold
Roof Performance
Levels
Field wind
load, kPa
Edge wind
load, kPa
Corner wind
load, kPa
Field wind
load, kPa
Edge wind
load, kPa
Corner wind
load, kPa
Bronze -1.0 -1.3 -2.6 -1.0 -1.3 -2.6
Silver -1.1 -1.4 -2.7 -1.43 -1.82 -3.51
Gold -1.1 -1.4 -2.7 -1.65 -2.1 -4.05
Note: 1kPa = 20.9 lb/ft2.
Wind loads for Bronze categories are compliant with current NBCC requirements; wind loads for Silver and Gold categories are increased 30% and 50%,
respectively, from the NBCC code requirements.
July/August 2025 IIBEC Interface • 23
uplift load exceeds the self-weight of a rooftop
unit, the unit could tip over, causing damage
to the roof membrane. While CSA A123.265
includes some prescriptive requirements for the
anchorage of rooftop units, the main intent is to
design rooftop units, including their components
and anchorage, to meet the wind uplift loads
required for the roof assembly.
CSA A123.265 also addresses an issue related
to the rubbing of rooftop components against
the roof membrane system causing reduced
service life. The standard requires that gas lines
are mounted on supports at a minimum of
304 mm (12 in.) over the membrane surface to
limit the potential for gas lines to rub against
the roof membrane due to deflections between
the supports. Similarly, the standard requires
that lighting protection cables are secured to
thermally nonconductive supporting elements
to limit rubbing of the cables on the roof
membrane. The minimum spacing requirements
for the securement of cables are 914 mm
(36 in.), 304 mm (12 in.), and 203 mm (8 in.),
respectively, in the field, edge, and corner areas.
CSA A123.265 addresses the common issue of
corrosion of metal components in rooftop units
and resulting damage to the roof membrane
by requiring that rooftop units and their
components, including body stands, anchors,
and fasteners, be made out of nonferrous metals,
stainless steel, or hot-dip galvanized steel with a
coating designation of at least G-90.
RESISTANCE TO RAIN LOAD
Rainwater resistance of a roof assembly is a
function of the watertightness of the membrane
and flashings, the roof slope, drainage, flashing
construction, and the ability of the system to
evacuate the water.
The primary function of a roof assembly
is to prevent precipitation from entering the
space below by controlling and discharging the
rainwater collected on the roof to either a storm
water drainage system or the terrain adjacent
to the building. To ensure that roof assemblies
meet this objective, designers calculate rain
loads and design a roof drainage system.
The design process involves determining the
appropriate number of drains and size of drains
and scuppers, taking into account the roof
slope, the type of roof finish, and the type of
rainwater leaders. The number and size of drains
are calculated based on the rainfall information
from NBCC2 and the maximum permitted
hydraulic load of leader pipe available in OBC.3
The intent of the code is to ensure that the roof
drainage system can carry off rainwater from
the most intense rainfall that is likely to occur.
Therefore, to meet current code requirements
(which would be applicable to a Bronze
project), the designer needs to determine the
maximum 15-minute rainfall intensity for the site
location (1 in 10-year return), referred to as the
“concentration time.” This rainfall information
can be obtained from Table C-2 in the NBCC2
Appendix or the Ministry of Municipal Affairs and
Housing’s Supplementary Standard SB-1, Climate
and Seismic Data.16 The hydraulic load in liters
from a roof is equal to the maximum 15-minute
rainfall intensity multiplied by the sum of area
of the horizontal surface and one-half the area
of the adjoining vertical surface (with the areas
measured in square meters). For instance, based
on the NBCC2 Table C-2, the maximum 15-minute
rainfall intensity (1 in 10-year return) for Toronto
(City Hall) is 25 mm. NBCC2 Table C-2 also
provides information on 1-day rainfall that has
1 chance in 50 of being exceeded in any single
year. The 1-in-50-year return value 1-day rainfall
is used mainly to determine the additional
(structural) dead load due to ineffective drains.
Anticipated rain loads for Silver and Gold
level roof assemblies can be determined using
the Climate-RCI13 tool. Unlike the NBCC2 tables
used for Bronze assemblies, Climate-RCI13 only
provides 1-day rainfall projections. In absence
of the maximum 15-minute rainfall intensity
information, the extrapolation of 1-day rainfall
data in the Climate-RCI13 tool is suitable as long
as the structural systems will be designed to
handle the weight of the projected 1-day rainfall.
The 15-minute rainfall intensity can be calculated
using the percentage difference between the
1-day rainfall data for Silver and Gold roofs
from Climate-RCI13 and the 1-day rainfall
values from the 2020 edition of NBCC.2 Refer
to Table 3 showing an example of the rain load
determination using extrapolation for ‘severe’
and ‘extreme’ conditions.
Table 7.4.10.9 of Ontario Building Code
provides the maximum permitted hydraulic
load drained to a horizontal storm drainage
pipe at 2% roof slope. Based on the determined
rain load, assuming a drain and leader size of
152 mm (6 in.) with a drain slope of 2% under
the roof and a roof area of 9290 m2 (100,000 ft2),
a total of 14 drains is required. Refer to Table 4
showing comparative calculations for a 4” drain
and for ‘severe’ and ‘extreme’ conditions.
ROOF DRAINAGE SYSTEM
DESIGN
The intent of the building code is to discharge
rainwater off the roof at the earliest possible time,
but without adding stress to the drainage system
during rapid acceleration of rainfall intensity; this
purpose is achieved by allowing a certain amount
of time for the rainwater to flow across and down
the roof before it enters the gutter or drainage
system. To determine the drain size and number
of drains for an effective rooftop drainage system,
the building code directs the designer to use
the maximum 15-minute rainfall intensity and
hydraulic load calculations.
In addition to the current building code
requirement, CSA A123.265 prescribes maximum
runoff for rainwater by limiting the distance
between the roof perimeter and drains and
limiting the spacing between the drains. For
roofing systems in the Silver category, the
standard specifies that water on the surface
cannot run more than 10.7 m (35 ft) to a drain and
scupper. In the Gold classification, the maximum
distance to a drain or scupper is 6.1 m (20 ft).
Analysis shows that this maximum water runoff
distance requirement overwrites the current
code, adding a significant number of drains to the
roof and limiting the current industry practice of
using two-directional slopes and valleys. When
the limiting distance for maximum runoff for
rainwater is applied, to a 9,290 m2 (100,000 ft2)
roof, 45 roof drains are required for a roofing
system in the Silver category. The SIGDERS
TABLE 3. Rain load determination for Toronto, Ontario
Rain Load Calculation
Roof Area 9290 m2
15-minute rain intensity per NBCC2 25 mm
One Day rainfall per NBCC2 97 mm
15-minute rain intensity for ‘severe’ condition per Climate-RCI13 Unavailable
One Day rainfall for ‘severe’ condition per Climate-RCI13 116.69 mm
Extrapolated 15 min rain intensity = (25 mm * 116.69 mm) / 97 mm 30 mm
One Day rainfall for ‘extreme’ condition per Climate-RCI13 126 mm
Extrapolated 15 min rain intensity = (25 mm * 116.69 mm) / 97 mm 32.5 mm
24 • IIBEC Interface July/August 2025
committee intends to review this CSA A123.265
requirement given the impracticality of such an
installation, questionable performance in terms
of thermal bridging, and challenges related to
the continuity of air barrier and waterproofing.
Also, this drainage system requirement conflicts
with the intent of the building code to reduce
overstress on the drainage system.
RAINWATER RUNOFF
MANAGEMENT ON ROOF
SURFACES
Current industry practice in roof drainage design
is to achieve a 2% minimum positive slope toward
roof drains; typically, the roofing system will have
two-directional drainage achieved using sloped
structure toward a central valley with crickets
built using tapered insulation at the center that
lead runoff water to drains. This industry practice
is further reinforced in CSA A123.26,5 which
requires that roofing assemblies in the Silver
and Gold categories achieve the minimum 2%
positive slope for the main roof surface, which
also includes a back slope at the crickets that
is double the slope of the main roof. The Gold
requirement prescribes that the entire roof
structure to have a minimum of 2% positive slope.
Current industry practice also limits the
interference to free drainage on the roof surface
by suitably positioning rooftop units, rooftop
accessories, and other openings or by using
crickets around such interferences. For effective
management of the drainage path, CSA A123.265
includes a prescriptive requirement to position
rooftop units, rooftop accessories, and other
openings a minimum of 1.8 m (6 ft) away from
roof drains, low points, or valleys to avoid
restricting the flow of water to drains or scuppers.
RAINWATER DISCHARGE
Ensuring the effectiveness of drains and scuppers
is a critical part of handling the discharge
of rainwater. In addition to a prescriptive
requirement for the minimum drain diameter,
CSA A123.265 includes several qualitative
requirements for drains, such as the requirement
for a sump at drains, specifications regarding
the size and slope of the sump, and installation
of strains and screens with specific material
choices and securement. CSA A123.265 requires
a minimum drain diameter of 76 mm (3 in.) for
roofing assemblies in the Silver category and
102 mm (4 in.) for those in the Gold category. A
sump is required at each main drain measuring
minimum 1.2 × 1.2 m (4 × 4 ft), with a minimum
4% slope toward the drain. In the Silver and
Gold classifications, every drain is required to
have a corrosion-resistant metal strainer that
is compatible with the adjacent materials and
secured in place, and there must be drain screens
secured to the drain strainers in a minimum of
four locations to catch roof debris. These screens
must be at least 609 mm (24 in.) in diameter
and made from a corrosion-resistant material
that is compatible with the adjacent materials.
The screen must be installed with a zinc strip to
minimize the unintentional growth of vegetation.
In alignment with the current industry practice
to install secondary drainage for every roof area,
CSA A123.265 includes requirement to install
secondary drains or scuppers to manage the
overflow of rainwater in case of drain failures. The
standard requires a minimum scupper opening
height of 102 mm (4 in.) for roofing assemblies
in the Silver classification and 152 mm (6 in.) for
those in the Gold classification, and it prescribes
that a scupper must be installed a minimum of
51 mm (2 in.) above the finished roof surface
with proper flashing detail and located at the
lowest point of roof or roof perimeter. The
standard also prescribes that the width of a
scupper opening must not be less than the
circumference of the roof drain in the same roof
area. However, upon evaluation, it was noted that
a requirement to install scuppers with a width
equal to the circumference of the main drains
is excessive. For instance, the circumference
of a 76 mm (3 in.) diameter drain is greater
than 228 mm (9 in.) and the circumference of a
101 mm (4 in.)-diameter drain is greater than
305 mm (12 in.) This requirement is currently
being reviewed by the SIGDERS committee for
modification; in future editions of CSA A123.26,5
the requirement may specify that scuppers must
have the same diameter as the main drains or a
diameter equal to the height of the scupper.
Regarding the rainwater discharge onto
grade, CSA A123.265 calls for the termination
of drainpipe 457 mm (18 in.) above grade with
an elbow extension of 914 mm (3 ft) from the
building onto splash pads at the outlet and/
or counter-flashings on the wall. While this
arrangement is a common industry practice,
the requirement in the standard reinforces the
significance of keeping the water away from the
building as it is being discharged.
CONTINUITY OF
WATERPROOFING,
AIRTIGHTNESS, AND
WEATHER RESISTANCE
The CSA A123.265 roof performance
requirements for the ‘Silver’ and ‘Gold’
categories specify that roof membranes,
flashing systems, and other roof penetrations
must be designed to be watertight and comply
with CAN/ULC-S742, Standard for Air Barrier
Materials—Specification.17 These requirements
align with current industry practices for
waterproofing and air barriers in roof assemblies.
In addition, CSA A123.265 includes
requirements to enhance the weather resistance
of roof assemblies by limiting the impacts of
snow accumulation, wind-driven rain, and
water splashing off the roof membrane surface.
The current common industry practice is for
a 203 mm (8-in.) membrane upturn at roof
penetrations and openings, including skylights,
fire walls, roof curbs, transitions, and changes in
plane in the interior field of the roof. According
to CSA A123.26,5 roof assemblies in the Silver
category must have an upturn of 355 mm (14 in.)
and those in the Gold category must have a
457 mm (18 in.) upturn. The membrane upturn
requirement on an exterior wall assembly within
the field of a roof assembly may pose challenges
TABLE 4. Number of drains and drain size determination for Toronto, Ontario
Determination of Drains
Volume of rainwater (9290 m2 x 25 mm = 232.25 m3) 232,250 liters
Hydraulic load of 4 in. diameter drain/drainpipe and 2% slope of drainpipe per
Table 7.4.10.9 in OBC3 5,970 liters
Number of 4 in. drains = 232,250 liters / 5,970 liters 39 drains
Hydraulic load of 6 in. diameter drain/drainpipe and 2% slope of drainpipe per
Table 7.4.10.9 in OBC3 17,600 liters
Number of 6 in. drains = 232,250 liters / 17,600 liters 14 drains
Volume of rainwater for ‘severe’ condition (9290 m2 x 30 mm = 278.70 m3) 278,700 liters
Number of 6 in. drains = 278,700 liters / 17,600 liters 16 drains
Volume of rainwater for ‘extreme’ condition (9290 m2 x 32.5 mm = 301.92 m3) 301,925 liters
Number of 6 in. drains = 301,925 liters / 17,600 liters 18 drains
Note: 1 in. = 25.4 mm; 1 ft =0.305 m; 1 gal. = 3.79 L.
July/August 2025 IIBEC Interface • 25
when the insulation is positioned within stud
cavities. It could create a situation in which
vapor retarder is doubled in the wall assembly.
The upturn for the membrane flashing at the
parapets is required to be at 304 mm (12 in.).
INSPECTION REQUIREMENTS
The wind and rain sections of CSA A123.265
both specify need for independent inspectors
to conduct quality assurance observations. For
the Silver category, the requirement is to retain
an independent inspector for at least 25% of
the days of work, during major stages of the
roofing application, including completion. The
intent is for the inspector to review whether
the work conforms to the standard, to the
applicable governing building code, and to any
quality assurance metrics established by the
design specifications. For the Gold category, the
requirement is to retain an independent inspector
for 100% of the days of work. CSA A123.265 offers
alternative options such as in situ testing of the
roof assembly for wind uplift, leak detection
system for rain penetration, and flood testing of
penetration flashings to either substitute for or
reduce the 100% inspection requirement. These
alternatives are discussed in later sections.
CSA A123.265 requirements for quality
assurance inspections conveys the criticality of
construction reviews for a proper installation of
the roof assembly. However, when a building
envelope consultant with expertise in roofing
is involved in the project, the intent of this
requirement can be met without engaging an
independent quality assurance inspector. If the
requirement were modified to include a review
by the already involved building envelope
consultant with expertise in roofing as an
alternative to a quality assurance inspector, that
would avoid duplication in some projects and
thus lower the costs of Gold and Silver projects.
In addition to the construction reviews
as mandated by the CSA A123.26,5 it is
recommended to conduct the following:
review of project specifications (including
project-specific wind uplift loads); shop drawings
and submittals; wind uplift resistance report
from the third-party laboratory; and mock-ups to
establish the standard of acceptance. The above
is recommended to be conducted by a qualified
building envelope consultant or an independent
quality assurance inspector.
In Situ Negative Pressure
Uplift Test Option
Annex B of CSA A123.265 includes an alternative
option for PARSs and AARSs to reduce the quality
assurance inspections particularly related to wind
uplift resistance for the Gold category. In lieu
of construction reviews for 100% of the project
days, in situ negative pressure uplift testing as
described in Annex B of CSA A123.265 allowing
reduction of quality assurance inspections to
50% of project days. A minimum of two tests is
required for every 5600 m2 (60,300 sq. ft.) of roof
area. The testing uses an in-situ pressure chamber,
with deflection and pressure sensors mounted on
the selected roof areas. The deflection of the roof
membrane is monitored visually through a port
and deflection sensor as the pressure differential
is increased by increments of 720 Pa (0.104 psi)
at 60-second intervals to a termination test
pressure meeting project-specific requirements.
While there is no direct correlation between this
field test and the laboratory testing specified in
CSA A123.21,1 the in-situ testing results provide
a good understanding of the performance of the
roof assembly and may identify noncompliant
installation.
Leak Detection System Option
Leak detection systems may be installed as
an integral part of the assembly at the time of
construction, or they can be installed using a
nondestructive technique within one or two years
after completion of construction. CSA A123.265
specifies that an integral leak detection system
installed during construction is suitable to
reduce the Gold category requirement for quality
assurance inspections from 100% to 25% of days.
Watertightness Testing Option
As an alternative option to the Gold category
requirement of quality assurance inspection for
watertightness on 100% of days, CSA A123.265
allows the option of conducting flood testing.
The specified testing method is a modified
version of ASTM D5957, Standard Guide for Flood
Testing Horizontal Waterproofing Installations,18
wherein a minimum test area of 3 × 3 m
(9.8 × 9.8 ft) with at least one plumbing vent
or any other roof penetration is flooded to a
minimum depth of 25 mm (1 in.) for 24 hours to
evaluate for water leaks.
While the test area is defined, the
CSA A123.265 standard does not indicate the
number of such tests per roof or the number of
tests for a certain extent of roof area. It is the
authors’ opinion that the number of tests be
determined by the number of roof areas defined
by the direction of slope and the selection of the
test area by the quality assurance inspector.
SUGGESTIONS FOR FURTHER
DEVELOPMENT OF CSA A123.26
AND ASSOCIATED TOOLS
In general, CSA A123.265 streamlines various
requirements to meet the wind and rain
effects of anticipated climate severities on roof
assemblies. As the first design standard of its
kind, it addresses several of the critical issues
related to roof assemblies. However, it could be
further enhanced to address the following:
• Given the projected increase in temperature
due to climate change, in addition
to the measures to counter the high wind
conditions and increased rainfall, the standard
may include in the future additional
requirements focused on roof membrane
material performance countering the temperature
increase. It is recognized that additional
research is required in this regard.
• Climate-RCI13 estimates anticipated climate
severities for wind, rain, and heat;
this tool may require further refinement to
include additional metrics for freeze- thaw
cycles, snow accumulations, hail, and
so on. Similarly, CSA A123.265 could be
expanded to include requirements to
counter such climate severities.
• CSA A123.265 includes prescriptive
requirements, both quantitative and qualitative,
for the Silver and Gold categories,
while defaulting to current codes and
industry practices for the Bronze category.
However, qualitative industry practices
vary significantly across regions, provinces,
and jurisdictions. It may therefore
be prudent to revise the standard to document
qualitative prescriptive requirements
for the Bronze category. For example, the
requirement for membrane upturns at
penetrations might be specified.
• CSA A123.265 clearly illustrates the significance
of the high wind conditions anticipated
at the parapet and includes some
recommendations for the structural integrity
of the parapet assembly, membrane,
and cladding components attached to the
parapet, including cap flashings and their
components. This topic, particularly the
requirements for the substrate to which
these components are secured, can be
further detailed. Additional requirements
could help address air-barrier continuity
challenges at the base of parapet where
the parapet is part of the main structure.
• CSA A123.265 may further develop the
mounting requirements for rooftop
add-ons, specifying whether they are
allowed to be floating (not secured to the
roof deck, but supported by self-weight
or added weight) on the roof assembly
or secured to main structural system. If
floating, the standard may further include
requirements about the required compressive
strength of the roof assembly and
26 • IIBEC Interface July/August 2025
components, and about required isolators
to reduce damage to the roof assembly.
• As discussed, CSA A123.265 could be
expanded to include requirements for specification
review, preconstruction meetings,
submittals (including the test reports), shop
drawing reviews, and mock-up reviews for
standard of acceptance. These requirements
would be in addition to the requirements for
periodic quality assurance reviews. Also, as
discussed, a review by a qualified building
envelope consultant might be offered as an
acceptable alternative to the requirements
for third-party quality assurance inspections.
• Considering that the intent of CSA
A123.265 is to help sustain the service life
of the roof assembly, the standard may
be expanded to include requirements for
maintenance during operation, such as
requirements for periodic reviews and predetermined
maintenance activities, including
repairs and renewals.
CONCLUSION
With the changing climate and the likelihood
of adverse weather conditions in the future,
the design and construction of roof assemblies
capable of resisting project-specific wind uplift
values as required by the building code is just a
starting point to achieve durable and resilient roof
assemblies with long service lives. CSA A123.265
aims to enhance the resilience of roof assemblies,
particularly low-slope membrane roofs, against
future climatic conditions by incorporating
anticipated wind and rain loads, using data
from Climate-RCI13 and improving the quality
of roofing details. The requirements in the
standard, both quantitative and qualitative, are
intended to improve the performance of the roof
assemblies and ensure durability by countering
future climate severities, by reducing wind uplift
failures, water ingress issues, safety issues, and
maintenance. The standard also provides clearer
guidelines for construction practices, which can
support designers across regions, provinces and/
or jurisdictions.
REFERENCES
1. CSA Group. 2020. Standard Test Method for the
Dynamic Wind Uplift Resistance of Membrane-Roofing
Systems. CSA/A123.21:20. Toronto, ON: CSA Group.
2. National Research Council of Canada (NRC). 2020.
National Building Code of Canada. Ottawa, ON; NRC.
3. Ministry of Municipal Affairs and Housing. 2012.
Ontario Building Code (OBC). Toronto, ON.
4. Roofing Contractors Association (RCABC), “Roofing
Practices Manual – Official Manual of the RoofStar
Guarantee Program.” https://rpm. rcabc.org/index.
php?title=Main_ Page. Langley, BC.
5. CSA Group. 2021. Performance Requirements for
Climate Resilience of Low Slope Membrane Roofing
Systems. CSA/A123.26:21. Toronto, ON: CSA Group.
6. S. Ramachandran, M. Summerfield, and A.E. Perri.
2023. “Wind Uplift Failure of a Roof Assembly:
The ‘Perfect Storm.’ Pushing the Envelope Canada
(Spring): 17-21. https://obec.on.ca/sites/default/
uploads/files/newsletter/Spring- 2023-articles/
article5.pdf.
7. National Research Council of Canada (NRC). 2023.
“Wind Load Calculators for Roof Cladding and
Vegetated Roof Assembly.” https://nrc.canada. ca/
en/research-development/ products-services/
softwareapplications/wind-load-calculatorsroofcladding-
vegetated-roof-assembly.
8. Canadian Roofing Contractors Association (CRCA).
2018. “Roofing Contractors and Designers
Responsibility.” https:// roofingcanada.com/
bulletin/ roofing-contractors-and-designers-responsibility.
9. Klassen, J. 2021 “Understanding the British
Columbia Building Code. Part 3: Roof Design: From
Code to Specification.” Roofing BC Magazine 18 (3):
16-26. https://www. mediaedgemagazines.com/
roofingcontractors-association-of-britishcolumbiarcabc/
rc213.
10. Single Ply Roofing Industry (SPRI). 2020. Wind
Design Standard Practice for Roofing Assemblies.
ANSI/SPRI WD-1. Waltham, MA: SPRI. https:// www.
spri.org/download/ansi-spri_ standards_2020_
800.992.7663 | www.versico.com
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CALIFORNIA
NEVADA
OREGON IDAHO
WASHINGTON
MONTANA
WYOMING
SOUTH DAKOTA
NORTH DAKOTA
MINNESOTA
WISCONSIN
MICHIGAN
INDIANA
ILLINOIS
NEBRASKA
KANSAS
NEW MEXICO
OKLAHOMA
LOUISIANA
TEXAS
MISSISSIPPI ALABAMA
TENNESSEE
KENTUCKY VIRGINIA
MARYLAND
DELAWARE
MASSACHUSETTS
NEW YORK
MAINE
WEST
VIRGINIA
PENNSYLVANIA
MISSOURI
IOWA
OHIO
GEORGIA
ARKANSAS
UTAH
ARIZONA
FLORIDA
NEW JERSEY
RHODE ISLAND
CONNECTICUT
NEW HAMPSHIRE
Helena
Billings
Casper
Havre
Jeffery City
Cody
Miles City Bismarck
Minot
Fargo
Minneapolis
Des Moines
Springfield
Hot Springs
Dallas
Austin
El Paso
Albuquerque
Colorado Springs
Roswell
Santa Fe
Denver
Cheyenne
Breckenridge
Grand Junction
San Antonio
New Orleans
Boothville
Houston
Cedar Rapids
Iowa City
Columbia Indianapolis
Cincinnati
Charlotte
Columbia
Raleigh
Roanoke
Fort Wayne
Milwaukee
NORTH CAROLINA
SOUTH
CAROLINA
Augusta
Valdosta
Tallahassee
Brownsville
COLORADO
VERMONT
July/August 2025 1160462_Editorial.indd 1 IIBEC Interf2a0c/06e/2 5 • 4 :1267ĐAM
restructure/wd-1/ANSI-SPRI-WD-1-020-Wind-Design-
Standard-Practice-for-Roofing- Assemblies_v2.pdf.
11. Engineers Canada. “Public Policy. Climate Change
and Engineering.” https://engineerscanada.ca/publicpolicy/
climate-change-and-engineering.
12. National Research Council of Canada (NRC), 2020.
National Energy Code of Canada for Buildings. NECB.
Ottawa, ON.
13. National Research Council of Canada (NRC). 2021.
“Climate-RCI.” https://nrc.canada.ca/en/researchdevelopment/
products-services/ software-applications/
climate-rci.
14. SPRI. 2011. Wind Design Standard for Edge Systems
Used with Low Slope Roofing Systems. ANSI/SPRI/FM
4435/ES-1. Waltham, MA; SPRI. https://www.spri.org/
download/ansispri_ standards_2020_restructure/
es-1/ANSI_SPRI_FM-4435- ES-1_2011_08042020.
pdf
15. CSA Group. 2021. Standard Test Method for Wind
Resistance of Modular Vegetated Roof Assembly.
CSA A123.24:21. Toronto, ON: CSA Group.
16. Ministry of Municipal Affairs and Housing (MMAH).
2014. Supplementary Standard SB-1– Climate and
Seismic Data. Toronto, ON: MMAH Building and
Development Branch.
17. ULC Standards. 2016. Standard for AirBarrier
Materials—Specification. CAN/ULC
S742:2011-R2016. Northbrook, IL: ULC Standards.
18. ASTM International. 2021. Standard Guide for Flood
Testing Horizontal Waterproofing Installations. ASTM
D5957-98(2021). West Conshohocken, PA: ASTM
International.
ABOUT THE AUTHORS
Sathya
Ramachandran has
24 years of experience
in building science
consulting and research,
with a focus on such
high-performance goals
as durability, resilience,
energy conservation,
and occupant comfort
of building envelope
assemblies. He has
provided consulting services for various building
types across North America and has advanced
education in building science. He has strong
knowledge, experience, and attention to detail in
the areas of building science principles, material
composition, regulations, different assemblies,
and components. He is a voting member of
the ASTM International E06 Committee for
Performance of Buildings and represents EXP at
SIGDERS committee meetings.
Over his 30-year career,
Bruno Bernard has
developed an in-depth
knowledge of roofing
materials and their
behavior. Since 2016,
he has headed the
EXP roofing testing
laboratory, the only
laboratory recognized
by UL DAP in Canada
for the CSA A123.21
standard (Standard Test Method for Dynamic
Wind Uplift Resistance of Membrane Roofing
Systems). His duties include laboratory testing,
in situ testing, and consulting expertise. He
sits on the SIGDERS (Special Interest Group for
the Dynamic Evaluation of Roofing System)
committee and other related task groups.
Please address reader comments to
chamaker@iibec.org, including
“Letter to Editor” in the subject line, or
IIBEC, IIBEC Interface Journal,
434 Fayetteville St., Suite 2400,
Raleigh, NC 27601
SATHYA
RAMACHANDRAN
BRUNO BERNARD
Unburdening Overburden
Considerations for Commercial
Roofing
MATT BRAUN, PE
Designing Low Slope Roofing for
Climate Change
ROBERT HEMPHILL, RBEC,
RRC, RWC, REWC
KIMBERLY FAJARDO,
RRO
IIBEC REGION V SUMMER
WORKSHOP
AT THE WSRCA CONVENTION
Please join us at the IIBEC Chapters of Region V Technical Seminar on October 1, 2025 at the
Paris Hotel in conjunction with the WSRCA 2025 Convention.
The program include five (5) sessions and provides 6.0 IIBEC and/or AIA learning units which.
The cost of this program is $250.00 for IIBEC members and $300.00 for non-members.
Registration for this program includes admission to the Western Roofing Expo trade
show on both Monday (9/29/25) and Tuesday (9/30/25)
What Does a Building Enclosure
Consultant Need to Know About
CLT?
Fene-frustration: The Headaches
of Windows
Code Updates: Learn about
important roofing related building
codes that affect both steep and
low slope roofing projects
DARBI KRUMPOS, CDT,
BECXP, CXA+BE
ERICA REYNOLDS, PE, RA,
FMPC
DANIEL J CUPIT
11620846 4•_E d IitIoBriaEl.Cind Idn t1erface 20/06/25 3:56ĐAM July/August 2025