Code and Wind - Revision history

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2023-03-16T16:30:58Z

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James Klassen: /* Introduction */

2023-03-16T16:30:23Z

‎Introduction

James Klassen at 18:38, 3 November 2021

2021-11-03T18:38:23Z

James Klassen: /* A third way */

2021-10-22T15:17:49Z

‎A third way

James Klassen at 17:05, 24 September 2021

2021-09-24T17:05:58Z

James Klassen: /* Good neighbours */

2021-09-24T17:04:11Z

‎Good neighbours

James Klassen: /* A third way */

2021-09-24T16:53:13Z

‎A third way

James Klassen: /* Begin with the end */

2021-09-24T16:52:49Z

‎Begin with the end

James Klassen: /* Alterations and new roofing */

2021-09-24T16:50:42Z

‎Alterations and new roofing

James Klassen: /* Why wind matters */

2021-09-24T16:48:39Z

‎Why wind matters

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 </gallery>
 ==Introduction==
-Membrane roofs are ubiquitous on industrial, commercial, and institutional buildings and cover many multi-family and some single-family Part 9 structures.  But a poorly designed and constructed membrane roof can succumb to the powerful uplift forces of wind, leaving the building interior vulnerable to the weather.  Flying roof material can also pose a serious risk to public safety.  Designing a wind-resistant membrane roof system is prudent.   It is also a Code requirement.  In this article on the British Columbia Building Code, we look at why wind matters and what the Code has to say about wind-resistant membrane roofs for Part 3 buildings.
+Membrane roofs are ubiquitous on industrial, commercial, and institutional buildings and cover many multi-family and some single-family Part 9 structures.  But a poorly designed and constructed membrane roof can succumb to the powerful uplift forces of wind, leaving the building interior vulnerable to the weather.  Flying roof material can also pose a serious risk to public safety.  Designing a wind-resistant membrane roof system is prudent.   It is also a Code requirement.  In this article on the British Columbia Building Code, we look at why wind matters and what the Code has to say about wind-resistant membrane roofs for Part 3 buildings (to continue reading this article as a PDF, click [https://rpm.rcabc.org/images/1/12/The_Building_Code_and_Wind_-_Summer_2021_%28Roofing_BC%29.pdf '''here'''])
 ==Why wind matters==

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 :Part 2: The Building Code and wind
 :Part 3: Design Responsibility: from Code to Specification
-You can find these articles in both the printed and digital editions of Roofing BC, the trade magazine published by the RCABC. You can also watch the video presentation, “Blown Away: Code Requirements for Membrane Roofs”, that addresses several articles in this series.
+You can find these articles in both the printed and digital editions of '''Roofing BC''', the trade magazine published by the RCABC. You can also watch the video presentation, [https://www.youtube.com/watch?v=fvq5M_tQh4s “Blown Away: Code Requirements for Membrane Roofs”], that addresses several articles in this series.
 The content on this page has been adapted from the original published article in [https://www.mediaedgemagazines.com/roofing-contractors-association-of-british-columbia-rcabc/rc212/ ''Roofing BC'' (Summer 2021)].

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 ===A third way===
-Finally, we have to confront the ultimate question: what if neither a Tested Assembly nor an assembly with proven past performance will work?  The answer is (sort of) in the Notes to Part 5.  There, provision is made to extrapolate the roof securement using the ANSI-SPRI standard WD-1[[#Footnotes|<sup><small>14</small></sup>]].  However, that provision is not exactly a “Get out of Jail Free” card.  The extrapolation is limited to mechanically attached systems.  It does not apply to adhered systems or even to hybrid systems (secured with a combination of mechanical fasteners and adhesives).  For those, the securement of the roof system should be custom-engineered and may have to be extrapolated from Tested Assembly data.
+Finally, we have to confront the ultimate question: what if neither a Tested Assembly nor an assembly with proven past performance will work?  The answer is (sort of) in the Notes to Part 5.  There, provision is made to extrapolate the roof securement using the ANSI-SPRI standard WD-1[[#Footnotes|<sup><small>14</small></sup>]].  However, that provision is not exactly a “Get out of Jail Free” card.  The extrapolation method has some limitations, and the reader should become familiar with the latest edition of the Standard.
 ==Good neighbours==

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 Roof design is complicated business.  Ultimately, good roof design must be rooted in a commitment to take care of each other – our neighbours.  Experience tells us that designing and building a roof that is resilient under pressure, to serve those who will live and work inside the building it protects, simply is the right thing to do.  As designers and constructors, we do more than simply build roofs.  Together, we create safe, habitable communities.
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 ===A third way===
-Finally, we have to confront the ultimate question: what if neither a Tested Assembly nor an assembly with proven past performance will work?  The answer is (sort of) in the Notes to Part 5.  There, provision is made to extrapolate the roof securement using the ANSI-SPRI standard WD-1 .  However, that provision is not exactly a “Get out of Jail Free” card.  The extrapolation is limited to mechanically attached systems.  It does not apply to adhered systems or even to hybrid systems (secured with a combination of mechanical fasteners and adhesives).  For those, the securement of the roof system should be custom-engineered and may have to be extrapolated from Tested Assembly data.
+Finally, we have to confront the ultimate question: what if neither a Tested Assembly nor an assembly with proven past performance will work?  The answer is (sort of) in the Notes to Part 5.  There, provision is made to extrapolate the roof securement using the ANSI-SPRI standard WD-1[[#Footnotes|<sup><small>14</small></sup>]].  However, that provision is not exactly a “Get out of Jail Free” card.  The extrapolation is limited to mechanically attached systems.  It does not apply to adhered systems or even to hybrid systems (secured with a combination of mechanical fasteners and adhesives).  For those, the securement of the roof system should be custom-engineered and may have to be extrapolated from Tested Assembly data.
 ==Good neighbours==

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 The RPM classifies roof systems as either waterproofing or water-shedding.  The latter uses gravity to shed water away from the structure.  Water-shedding roofs are not designed to work under any kind of hydrostatic pressure and are commonly used on Part 9 structures.  Asphalt shingles, cedar shakes and shingles, and metal panel roofs, all are water-shedding materials.
-Waterproofing roof systems, on the other hand, resist hydrostatic pressure.  These roofs are usually (but not exclusively) “flat” (sloped toward drains less than 1:6), and most are insulated beneath the weathering surface.  Some are insulated above it .  The weathering surface is commonly referred to as a membrane, but not all membranes are the same; some are liquid-applied, others comprised of sheets of material welded together to form a monolithic covering (singular in form and function).
+Waterproofing roof systems, on the other hand, resist hydrostatic pressure.  These roofs are usually (but not exclusively) “flat” (sloped toward drains less than 1:6), and most are insulated beneath the weathering surface.  Some are insulated above it[[#Footnotes|<sup><small>10</small></sup>]].  The weathering surface is commonly referred to as a membrane, but not all membranes are the same; some are liquid-applied, others comprised of sheets of material welded together to form a monolithic covering (singular in form and function).
-Membrane-type assemblies are used on most “Part 3 buildings”, and on some “Part 9” structures.  While Division B, Part 9 does not provide expressed or even complete “acceptable solutions” for membrane roof systems , the requirements for membrane roofs employed on both Part 3 and Part 9 buildings find common ground in Division B, Part 5, which is where we now turn.
+Membrane-type assemblies are used on most “Part 3 buildings”, and on some “Part 9” structures.  While Division B, Part 9 does not provide expressed or even complete “acceptable solutions” for membrane roof systems[[#Footnotes|<sup><small>11</small></sup>]], the requirements for membrane roofs employed on both Part 3 and Part 9 buildings find common ground in Division B, Part 5, which is where we now turn.
 Part 5 (Division B) Environmental Separation is comprised of ten sections, each focused on a performance criterion or issue, like Heat Transfer or Air Leakage, rather than on a type of assembly, such as walls or the roof.  A brief examination of Section 5.6. Precipitation offers little about roofs beyond several broad functional statements – a roof must “minimize ingress of precipitation into the component or assembly” (don’t all roofs have to do this?) and it must “prevent ingress of precipitation into interior space” (yes, it says that).  Nothing is said about wind.
-In Section 5.1. General, we find a few clues to the subject of wind.  Article 5.1.4.1. addresses “environmental loads”.  That looks promising since wind is an “environmental” phenomenon.  A quick read leads us further along in our quest: roofing must be designed to conform to the requirements in Subsection 5.2.2. “with regard to wind up-lift imposed on roofing….”  In Section 5.2. Loads and Procedures  we find the grail – Article 5.2.2.2. Determination of Wind Loads.  Article 5.2.2.2. deals with membrane roof systems “that separate dissimilar environments or are exposed to the exterior”, and which may be “<span class="recommended">subject to wind load, and…[are] required to be designed to resist wind load</span>” (red colour added for emphasis).  The Article is reproduced below; blue text in the Code indicates new material introduced in the Code in 2018.
+In Section 5.1. General, we find a few clues to the subject of wind.  Article 5.1.4.1. addresses “environmental loads”.  That looks promising since wind is an “environmental” phenomenon.  A quick read leads us further along in our quest: roofing must be designed to conform to the requirements in Subsection 5.2.2. “with regard to wind up-lift imposed on roofing….”  In Section 5.2. Loads and Procedures[[#Footnotes|<sup><small>12</small></sup>]] we find the grail – Article 5.2.2.2. Determination of Wind Loads.  Article 5.2.2.2. deals with membrane roof systems “that separate dissimilar environments or are exposed to the exterior”, and which may be “<span class="recommended">subject to wind load, and…[are] required to be designed to resist wind load</span>” (red colour added for emphasis).  The Article is reproduced below; blue text in the Code indicates new material introduced in the Code in 2018.
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 [[File:Code and Wind - Image 6.jpeg|thumb|center]]<br clear=all>
-Article 5.2.2.2 is not new to the Code .  What is new in Part 5 are the options by which a design can conform to these requirements.  The 2012 Code offered no guidance.  The design authority knew that the roof had to conform to the Code but had to look elsewhere for solutions.  Many designs (if they even paid attention to this somewhat obscure requirement) referenced what few standards industry had to offer, such as FM Global’s design specifications and approvals.  Today, the Code is specific and offers three pathways for compliance; none include FM standards or test methods.  All are performance-based.  Sentence (4) requires a roof to be designed using a tested roof assembly (“Tested Assembly”) (Sentence (4)).  Sentence (5) permits the use of a membrane system with “proven past performance” as an alternative to Sentence (4).  And in the Notes to Part 5, a third way is offered, which I will deal with separately.  Each of the first two merits brief comments.
+Article 5.2.2.2 is not new to the Code[[#Footnotes|<sup><small>13</small></sup>]].  What is new in Part 5 are the options by which a design can conform to these requirements.  The 2012 Code offered no guidance.  The design authority knew that the roof had to conform to the Code but had to look elsewhere for solutions.  Many designs (if they even paid attention to this somewhat obscure requirement) referenced what few standards industry had to offer, such as FM Global’s design specifications and approvals.  Today, the Code is specific and offers three pathways for compliance; none include FM standards or test methods.  All are performance-based.  Sentence (4) requires a roof to be designed using a tested roof assembly (“Tested Assembly”) (Sentence (4)).  Sentence (5) permits the use of a membrane system with “proven past performance” as an alternative to Sentence (4).  And in the Notes to Part 5, a third way is offered, which I will deal with separately.  Each of the first two merits brief comments.
 ===Tested Assemblies and Proven Past Performance===

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 Anyone who works with the Code knows that it applies to new buildings.  However, it does not apply only to new construction, a common misconception.  It also can be enforced for existing buildings.
-Wait, what?  Yes, it can be applied to existing buildings.  In Division A, Part 1 (Compliance), Article 1.1.1.1. Application of this Code  reads, “This Code applies to… d) an alteration of any building.”  Pretty much to the point, isn’t it?  If you are still picking yourself up off the floor after reading that, take a little heart.  Not everything that might constitute an alteration is covered by the Code.  To discern what is and is not a Code matter, let’s briefly examine Article 1.1.1.1. through the lens of Code objectives, and then see what Article 1.1.1.1. means for roofing.
+Wait, what?  Yes, it can be applied to existing buildings.  In Division A, Part 1 (Compliance), Article 1.1.1.1. Application of this Code[[#Footnotes|<sup><small>5</small></sup>]] reads, “This Code applies to… d) an alteration of any building.”  Pretty much to the point, isn’t it?  If you are still picking yourself up off the floor after reading that, take a little heart.  Not everything that might constitute an alteration is covered by the Code.  To discern what is and is not a Code matter, let’s briefly examine Article 1.1.1.1. through the lens of Code objectives, and then see what Article 1.1.1.1. means for roofing.
-You will recall what the Code is not : it is not a quality assurance standard.  At the risk of sounding facetious, neither is it an interior decorating guide.  Its objectives are quite defined and establishes minimum requirements for occupant accessibility, health, and safety.  Even then, the stated objectives of the Code (''Division A, Part 2'', '''Section 2.2. Objectives''') do not apply to every type of building governed by the Code (see ''Division A, Part 2'', '''Section 2.1. Application''').
+You will recall what the Code is not[[#Footnotes|<sup><small>6</small></sup>]]: it is not a quality assurance standard.  At the risk of sounding facetious, neither is it an interior decorating guide.  Its objectives are quite defined and establishes minimum requirements for occupant accessibility, health, and safety.  Even then, the stated objectives of the Code (''Division A, Part 2'', '''Section 2.2. Objectives''') do not apply to every type of building governed by the Code (see ''Division A, Part 2'', '''Section 2.1. Application''').
 For example, consider Objective OH1 Indoor Conditions.  In a nutshell, Objective OH1 states that the Code intends to “limit the probability that, as a result of the design or construction of the building, a person in the building will be exposed to an unacceptable risk of illness due to indoor conditions” because of “contact with moisture” (OH1.3).  Said a different way, and framed in the context of roof replacement, if the failure of an altered roof exposes building occupants to moisture, which could then make them ill, the Code applies to roofs on existing buildings.
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 Alteration means “a change or extension to any matter or thing or to any occupancy regulated by this Code.”  None of the key words in the definition for alteration (except the word building) are further defined, but notice the use of “or”, which means that an alteration can mean a material change in the building or a change in its occupancy (which means the way in which the building is or will be used).  Therefore, we must take the common sense of the requirement, namely that when a “thing” on a building is changed (a roof, for example), the Code applies to the change.
-As stated earlier, there are limits to the application of the Code.  Changing the exterior paint colour on a building would not be considered an alteration.  For that matter, buying a new kitchen range and discarding the old one also does not concern the Code (“This Code does not apply to…mechanical or other equipment and appliances not specifically regulated in these regulations”) .  On the other hand, removing and replacing a structural element of a building certainly qualifies as a “change” that concerns the Code, for every type of building (see Objective '''OS2 Structural Safety''').  Code objectives are the key to understanding what “change” means.
+As stated earlier, there are limits to the application of the Code.  Changing the exterior paint colour on a building would not be considered an alteration.  For that matter, buying a new kitchen range and discarding the old one also does not concern the Code (“This Code does not apply to…mechanical or other equipment and appliances not specifically regulated in these regulations”)[[#Footnotes|<sup><small>7</small></sup>]].  On the other hand, removing and replacing a structural element of a building certainly qualifies as a “change” that concerns the Code, for every type of building (see Objective '''OS2 Structural Safety''' [[#Footnotes|<sup><small>8</small></sup>]]).  Code objectives are the key to understanding what “change” means[[#Footnotes|<sup><small>9</small></sup>]].
 So much for the scope of the Code.  What does the Code have to say about membrane roofs?

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 On July 18, 2019 a severe windstorm blew through part of Saskatoon, Saskatchewan.  Winds registering 85 km/h in the vicinity ripped away the entire membrane roof from the steel building occupied by EFL Flooring.  The roof system was lifted off en masse.  The force from the wind and the failing roof was so strong it pulled rooftop mechanical equipment away, leaving gaping holes through the deck.  One employee was nearly crushed in the parking lot by falling roof materials.  Roof debris scattered across the street and down the block.  Moments later, rains followed.
-This is just one story.  There are others.  And all of them might have ended differently had the roof been designed and built to resist strong wind .  Of course, insurance often pays for wind damage and resulting loss from rain, but that really misses the point.  Disasters like the one in Saskatoon alter the lives and livelihoods of people – folks who are our neighbours.   And some of them never recover, lacking the resilience to cope .  Roofs should stay where they are built.  As designers and constructors of roofs, we can do better.  We must do better.
+This is just one story.  There are others.  And all of them might have ended differently had the roof been designed and built to resist strong wind[[#Footnotes|<sup><small>1</small></sup>]].  Of course, insurance often pays for wind damage and resulting loss from rain, but that really misses the point.  Disasters like the one in Saskatoon alter the lives and livelihoods of people – folks who are our neighbours.   And some of them never recover, lacking the resilience to cope[[#Footnotes|<sup><small>2</small></sup>]].  Roofs should stay where they are built.  As designers and constructors of roofs, we can do better.  We must do better.
-We often think of wind as a phenomenon that pushes .  Trees bend because wind pushes against them.  Waves crash on a beach because they are driven by wind.  Sailboats ghost gracefully in a bay because wind presses against the sails.  All true, but not all there is to know about wind.
+We often think of wind as a phenomenon that pushes[[#Footnotes|<sup><small>3</small></sup>]].  Trees bend because wind pushes against them.  Waves crash on a beach because they are driven by wind.  Sailboats ghost gracefully in a bay because wind presses against the sails.  All true, but not all there is to know about wind.
-“Wind is air moving from a place that has higher pressure to one that has lower pressure.”   Sometimes, this is a localized phenomenon where a ‘thermal’ carries warm air aloft, pulling cooler air in behind it.  Here on the south coast of British Columbia, faster warming land masses pull cool air in from the water, creating “inflow” winds; the reverse happens in late day as the land cools quicker than the nearby sea.  Microsystems abound in a region freckled with islands, large and small.  Big weather patterns revolve around high and low-pressure systems that develop both offshore and inland, and when the low-pressure centre is very low, resulting winds from air pulled into it can be violent.
+“Wind is air moving from a place that has higher pressure to one that has lower pressure.”[[#Footnotes|<sup><small>4</small></sup>]]   Sometimes, this is a localized phenomenon where a ‘thermal’ carries warm air aloft, pulling cooler air in behind it.  Here on the south coast of British Columbia, faster warming land masses pull cool air in from the water, creating “inflow” winds; the reverse happens in late day as the land cools quicker than the nearby sea.  Microsystems abound in a region freckled with islands, large and small.  Big weather patterns revolve around high and low-pressure systems that develop both offshore and inland, and when the low-pressure centre is very low, resulting winds from air pulled into it can be violent.
 Inasmuch as wind pushes, it also pulls.  Flowing over surfaces, wind creates negative pressure that can cause objects to move.  Slopes cause horizontally flowing wind to deflect upwards and around objects, but when wind strikes a building with flat roof areas, the flow around these structures induces negative pressure over the roof surface.  Powerful ‘sucking’ action can occur, and if the roof is not properly secured, the results can be catastrophic.

Code and Wind - Revision history

James Klassen: Replaced content with "{{Template:RPM Info}} __NOTOC__ __NONUMBEREDHEADINGS__ {{DISPLAYTITLE:{{FULL..."

James Klassen: /* Introduction */

James Klassen at 18:38, 3 November 2021

James Klassen: /* A third way */

James Klassen at 17:05, 24 September 2021

James Klassen: /* Good neighbours */

James Klassen: /* A third way */

James Klassen: /* Begin with the end */

James Klassen: /* Alterations and new roofing */

James Klassen: /* Why wind matters */

James Klassen: Replaced content with "{{Template:RPM Info}} NOTOC NONUMBEREDHEADINGS {{DISPLAYTITLE:{{FULL..."