|
|
| Line 18: |
Line 18: |
| | | | |
| | ====<big><span class="reference">Notes to Part 3</span></big>==== | | ====<big><span class="reference">Notes to Part 3</span></big>==== |
| − | <div id=A-3.1.1.1.></div>
| |
| − | :<big>'''A-3.1.1.1.'''</big> ('''Scope''')
| |
| − | :{{hilite | Wind exerts tremendous forces on a ''roof system'', regardless of roof type. While wind is commonly experienced as a “pushing” force, wind also generates “negative” (pulling or “uplift”) forces, particularly on flat roofs. These powerful forces can, if the ''roof system'' is poorly secured to the building’s structural elements, detach a portion or all of a ''roof system'' from the building|| 2021-October-30 }}.
| |
| − |
| |
| − | :{{hilite | The Code refers to these calculated forces as ''Specified Wind Loads'', which act in concert with the “responses of the roof system…[and therefore] are time-and-space dependent, and thus are dynamic in nature.” (CSA Standard ''A123.21 Standard test method for the dynamic wind uplift resistance of membrane-roofing systems'' (latest edition), 4.1). Because of this dynamic interplay between loads and a building’s structural capacities (the load paths between the roof system and other structural elements of the building), the ''Design Authority'' must design a roof capable of effectively absorbing and mitigating ''Specified Wind Loads''|| 2021-October-30 }}.
| |
| − |
| |
| − | :{{hilite | As stated earlier, the calculation of ''Specified Wind Loads'' falls under ''Division B, Part 4 Structural Design,'' '''4.1.7 Wind Loads''', while the securement of the roof components system to resist ''Specified Wind Loads'' is governed by ''Division B, Part 5 Environmental Separation,'' '''5.2.2.2 Determination of Wind Load'''|| 2021-October-30 }}.
| |
| − |
| |
| − | <div id=A-3.1.1.2.></div>
| |
| − | :<big>'''A-3.1.1.2.'''</big> ('''Intent''')
| |
| − | :{{hilite | In December 2018 the Province of British Columbia released a revised edition of the || 2021-October-30 }}[http://free.bcpublications.ca/civix/content/public/bcbc2018/?xsl=/templates/browse.xsl ''British Columbia Building Code''] {{hilite | (the "Code"), based on the 2015 ''National Building Code of Canada''. The 2018 Code includes a considerable expansion of the requirements in ''Division B, Part 4'' (see|| 2021-October-30 }} [http://free.bcpublications.ca/civix/document/id/public/bcbc2018/bcbc_2018dbp4s41r2 ''4.1 Structural Loads and Procedures'']{{hilite |, '''4.1.7 Wind Load''') applicable to the loads exerted on a roof system by wind. The careful reader will note that these Part 4 requirements apply to all Part 3 buildings and to some Part 9 structures|| 2021-October-30 }}.
| |
| − |
| |
| − | :{{hilite | While the expansion of Part 4 addresses the calculation of dynamic wind loads experienced by a roof assembly, Part 5 (Environmental Separation) specifies how a roof system should be secured to resist ''Specified Wind Loads'' (see || 2021-October-30}} [http://free.bcpublications.ca/civix/document/id/public/bcbc2018/bcbc_2018dbp5s52 ''5.2 Loads and Procedures'']{{hilite |, ''5.2.2.2 Determination of Wind Load'')|| 2021-October-30 }}.
| |
| − |
| |
| − | :{{hilite | Article 5.2.2.2 of the Code applies almost exclusively to ''Conventionally Insulated Roof Systems'' and is specifically oriented to sheet membrane roof systems. While sheet membrane ''Conventionally Insulated Roof Systems'' are prolific and perhaps the most common type of waterproofing roof system, the Code offers little guidance for other roof types, including uninsulated roof systems, liquid membrane systems and systems insulated above the membrane (referred to as “inverted” or “protected”). This Standard incorporates design and construction guidance, even where the Code appears to offer little or no support|| 2021-October-30 }}.
| |
| − |
| |
| − | :{{hilite | Proper securement of the roof system, to resist wind uplift loads, is good practice. It also fulfills the design and construction objectives of the Code, to guard public safety, and it supports the design objectives of the '''''RoofStar Guarantee Program''''', to keep weather outside of the building. In this Part, the reader will find explanatory notes and aids in the design and construction of a roof intended to be Code-compliant|| 2021-October-30 }}.
| |
| − |
| |
| − | <div id=A-3.1.4.2.></div>
| |
| − | :<big>'''A-3.1.4.2.'''</big> ('''Specifying a Tested Assembly''')
| |
| − | :''Tested Assemblies'' are roof assemblies that have been selected by the membrane manufacturer, installed on a specific ''deck'' type, secured using one of three systems, and tested by an independent certified laboratory to determine the limits of the assembly’s ability to resist negative wind pressure (loads), or ‘wind uplift’. Each of the three methods is expressed with an acronym:
| |
| − | ::[http://rpm.rcabc.org/index.php?title=MARS_Tested_Roof_Systems '''MARS'''], or ''Mechanically Attached Roof Systems'' – these ''systems'' are held in place only with mechanical fasteners that are installed at the membrane layer.
| |
| − | ::[http://rpm.rcabc.org/index.php?title=PARS_Tested_Roof_Systems '''PARS'''], or ''Partially Adhered Roof Systems'' – both mechanical fasteners and adhesives are used as a hybrid method of securement; the membrane is always adhered, using an applied adhesive or heat-welding.
| |
| − | ::[http://rpm.rcabc.org/index.php?title=AARS_Tested_Roof_Systems '''AARS'''], or ''Adhesive Applied Roof Systems'' – these are membrane roofs secured only with adhesives or heat-welded components.
| |
| − |
| |
| − | <div id=A-3.2.1.1></div>
| |
| − | :<big>'''A-3.2.1.1'''</big> ('''Substituting Materials Used in a Tested Assembly''')
| |
| − | :{{hilite |''Tested Assembly'' values (Dynamic Uplift Resistance) are predicated on a specific combinations (system) of materials. Each material in the ''system'' possesses unique "cohesive properties" (internal strength and integrity) and is linked to the adjacent material in a particular way that may depend on a material’s unique "adhesive properties"|| 2021-October-30 }}.
| |
| − |
| |
| − | :{{hilite |The substitution of material components in a ''Tested Assembly'' is not contemplated by ''CSA-A123.21'', but Annex F (a non-mandatory part of the CSA Standard, included at the back of the Standard document for information only) includes three decision processes for MARS, PARS and AARS assemblies, to guide the ''Design Authority'' when a substitution is desirable or necessary (ref. ''A123.21 Standard test method for the dynamic wind uplift resistance of membrane-roofing systems'', Annex F (informative) Component swap flow diagrams). Using Annex F as a basis for guidance, the following standards and guiding principles apply for the purpose of issuing a '''''RoofStar Guarantee'''''|| 2021-October-30 }}.
| |
| | | | |
| | ====<big><span class="reference">Notes to Part 4</span></big>==== | | ====<big><span class="reference">Notes to Part 4</span></big>==== |
| | | | |
| | ====<big><span class="reference">Notes to Part 5</span></big>==== | | ====<big><span class="reference">Notes to Part 5</span></big>==== |
| − | <div id=A-5.1.3.1.></div>
| |
| − | :<big>'''A-5.1.3.1.'''</big> ('''Required Use of Overlays''')
| |
| − | :A roof ''deck'' overlay (also called a system underlay) is installed as part of the ''roof system'', on the top surface of the roof ''deck'' but beneath other roofing materials. These products are most commonly affixed to steel ''decks'' to provide a level surface for the roof membrane, to support air or vapour control layers, or to serve as a thermal barrier between the roof deck and combustible insulation. Roof ''deck'' overlay materials may also be applied to other types of supporting ''deck'' structures, depending on the roof design criteria.
| |
| | | | |
| | ====<big><span class="reference">Notes to Part 6</span></big>==== | | ====<big><span class="reference">Notes to Part 6</span></big>==== |
| − | <div id=A-6.1.1.1.></div>
| |
| − | :<big>'''A-6.1.1.1.'''</big> ('''Design''')
| |
| − | :Air and vapour control layers, along with thermal barriers, water resistive barriers and water-shedding surfaces, serve to separate the outside environment from the interior environments of a structure. Continuous air control layers are perhaps the most critical. Codes in each jurisdiction, and the '''National Energy Code''' (2011), require the selection and proper installation of “a continuous air barrier system comprised of air-barrier assemblies to control air leakage into and out of the conditioned space” (NEC 2011).
| |
| − |
| |
| − | :'''Air control layers''' regulate and often prohibit the “flow of air through the building enclosure, either inward or outward” (''Guide for Designing Energy Efficient Building Enclosures'', '''Homeowner Protection Office'''). Controlling air flow into and out of conditioned spaces affects the performance of “thermally efficient enclosure assemblies” (ibid), impacts the potential for condensation in between materials, and directly influences rain water penetration of the building envelope.
| |
| − |
| |
| − | :'''Vapour control layers''' regulate or prohibit the movement of water vapour from one space to another by means of diffusion. Consequently, these control layers are referred to as either vapour-permeable or impermeable. Diffusion is a slow process, in contrast to air movement, and its regulation is not always mandatory or even desirable.
| |
| − |
| |
| − | :Any references in this ''Manual'' to installation methodologies, and any construction details that show air and vapour control layers, are merely illustrative and not prescriptive. Installers of continuous air and vapour control layer ''systems'' are urged to understand and comply with best practices for their application.
| |
| | | | |
| | ====<big><span class="reference">Notes to Part 7</span></big>==== | | ====<big><span class="reference">Notes to Part 7</span></big>==== |
| Line 99: |
Line 57: |
| | | | |
| | ====<big><span class="reference">Notes to Part 9</span></big>==== | | ====<big><span class="reference">Notes to Part 9</span></big>==== |
| − |
| |
| − | <div id=A-9.1.3.2.></div>
| |
| − | :<big>'''A-9.1.3.2.'''</big> ('''System Securement''')
| |
| − | :SBS-modified bituminous membranes are fabricated as rolled sheets and, when specified for use on roofs, are normally designed for application only on ''Flat'' or ''Low Slope'' structural roof decks and come in a variety of thicknesses and surface finishes. They may be reinforced with different materials (each reinforcement material exhibiting particular properties and offering different benefits), and may each be applied in one or more ways.
| |
| − |
| |
| − | :Most SBS-modified bituminous membranes are designed as two separate plies – a base and cap membrane – which are heat-welded together as a 2-ply assembly. Some are self-adhered or adhered to each other and to a substrate with mop-applied hot bitumen or with an adhesive (see below). A third ply is occasionally part of the manufacturer's specified ''system'' and may be required or simply is prudent for additional waterproofing protection in certain circumstances.
| |
| − |
| |
| − | :Common applications include:
| |
| − | :*'''Mechanically fastened''' (where the base membrane is affixed to the roof ''deck'' with self-drilling screws and load-distributing plates; the cap membrane is then torch-applied or adhered to the base)</span>.
| |
| − | :*'''Torch-applied''' (where torch heat brought to bear on the both the base and cap membranes liquefies the modified bitumen in the membrane so that it bonds with the substrate below)</span>.
| |
| − | :*'''Adhered'''</span>:
| |
| − | ::*'''Self-adhering''' (SA) (using a proprietary adhesive film bonded to the modified bitumen, SA membranes are often adhered with the help of a primer; occasionally, the base membrane is self-adhering, and the cap membrane is then torch-applied to the base)</span>.
| |
| − | ::*'''Cold-adhered''' (using bitumen-based or synthetic adhesive, this may sometimes be referred to as 'cold-applied’)</span>.
| |
| − | ::*'''Hot bitumen adhered''' (sometimes referred to as 'hot-mopped', 'hot-applied' or simply 'mopped', this application method applies to both the base and cap membranes, or may apply only to the base membrane; the cap, then, is torch-applied to the base membrane)</span>.
| |
| − |
| |
| − | <div id=A-9.3.3.3.></div>
| |
| − | :<big>'''A-9.3.3.3.'''</big>
| |
| − | :"Adhered" refers to a broad category of membranes that may be self-adhering, typically requiring a primer to enhance adhesion (refer to the manufacturer's published instructions), adhered with cold adhesives (synthetic or bitumen-based), or mop-applied with hot bitumen (bitumen that is melted in a kettle). Different requirements apply to each of these, depending on the membrane type, the method of application and the slope of the roof.
| |
| | | | |
| | ====<big><span class="reference">Notes to Part 10</span></big>==== | | ====<big><span class="reference">Notes to Part 10</span></big>==== |
| | | | |
| | ====<big><span class="reference">Notes to Part 11</span></big>==== | | ====<big><span class="reference">Notes to Part 11</span></big>==== |
| − | <div id=A-11.2.1.2.></div>
| |
| − | :<big>'''A-11.2.1.2.'''</big> ('''Roof Drains and Scuppers''')
| |
| − | :Roof drains are comprised mainly of two parts: a bowl or flange that is affixed to the roof deck with mechanical fasteners or a proprietary clamping mechanism; and an integral drain stem that connects the bowl or flange to the leader. Roof drains are sized according to the diameter of the drain stem. The appropriate size and number of roof drains for any given roof area is determined by the relevant building code in force (ref. ''British Columbia Plumbing Code, Division B, Part 2''; Article '''2.4.10.4 Hydraulic Loads from Roofs or Paved Surfaces''').
| |
| − |
| |
| − | :Roof drains can be further classified as {{hilite | '''''internal''''' or '''''external'''''. ''Internal roof drains''|| 2020-February-15 }} are connected to leaders located and connected to a storm building drain or sewer inside the exterior surface of a building. {{hilite | ''Internal roof drains'' may be made of cast iron (secured to the ''roof assembly'' with clamps) or from copper or aluminum, fashioned from spun components that are welded together and incorporate a flange around the drain bowl.
| |
| − |
| |
| − | :''External roof drains'' direct|| 2020-February-15 }} storm water outside the exterior surface of a building. {{hilite | ''Scuppers'' and ''overflow drains'' are the common types of ''external roof drains'', and may connect to leaders or simply drain freely.|| 2020-February-15 }} Any requirements for leaders and connections to leaders may be found in the applicable municipal and provincial building and plumbing codes (ref. ''British Columbia Building Code, Division B, 5.6.2.2 Accumulation and Disposal'').
| |
| | | | |
| | ====<big><span class="reference">Notes to Part 12</span></big>==== | | ====<big><span class="reference">Notes to Part 12</span></big>==== |
| Line 134: |
Line 67: |
| | | | |
| | ====<big><span class="reference">Notes to Part 14</span></big>==== | | ====<big><span class="reference">Notes to Part 14</span></big>==== |
| − | <div id=A-14.1.></div>
| |
| − | :<big>'''A-14.1.'''</big> ('''Design''')
| |
| − | :Membrane ''roof systems'' may be utilized for more than simple weather protection; they can be occupied by casual or regular users, for gardening, playing, lounging, or other leisure activities. Roofs that serve as amenity spaces require that the ''Design Authority'' pay particular attention to the ''system'' selection itself and, especially, to the protection of the roof membrane.
| |
| − |
| |
| − | :A ''Conventionally Insulated System'' is not appropriate for all types of use or ''roof coverings''. For example, the designed live loading for occupied spaces, or the weight of a ''roof covering'', may require the ''Design Authority'' to specify particular materials, and consequently to design a roof as a ''Protected Membrane Roof System''. Furthermore, some ''roof coverings'' require maintenance that may result in damage to ''Conventionally Insulated Systems''; ''Protected Membrane Roof Systems'' shield the sensitive membrane from this inevitability.
| |
| − |
| |
| − | :A ''Protected Membrane Roof System'' (often referred to as an "inverted roof") offers the designer many benefits, including</span>
| |
| − | :*longer lasting membranes.
| |
| − | :*capacity for heavier dead and live loads</span>.
| |
| − | :*only one control layer to seal and join with the rest of the building envelope</span>.
| |
| − | :*fewer waterproofing challenges around penetrations</span>.
| |
| − | :*the capacity for electronic leak detection (whether passive or monitored)</span>.
| |
| − |
| |
| − | <div id=A-14.1.4.3.></div>
| |
| − | :<big>'''A-14.1.4.3.'''</big> ('''Gravel''')
| |
| − | :Gravel used as a roof covering is different from its function as ballast on a ''Protected Membrane Roof System'' or ''Modified Protected Membrane Roof System''; gravel used as ballast is considered a means of securement and is covered in '''Part 3 SECURING the ROOF ASSEMBLY''' and in Part 9.
| |
| | | | |
| | <div class="col-md-12"> | | <div class="col-md-12"> |
