b'This requirement has been somewhat migated by the ability to e into the primary roof drain (previously not permied), but the storm drain has to be sized to accommodate 200 per cent of the hydraulic load if that approach is taken. Below is an illustraon of that: BUILDING CODEemergency roof drainIn my view, besides potential aestheticroof membrane 150 mm maximumconsiderations, there are no drawbacks or negatives from having excessprimary roof drainoverflow drainage capacity installedon the building. storm building drain to be sized for 200% of the calculated hydraulic loadFigure [A-2.4.10.4.(5).]: Storm building drain serving both the primary and emergency roof drainage systems.This may be an aempt to migate costs of the rst change, but while this proposed change will Get A Roof Your reduce costs, it may not be a best pracce. There have been examples of ice blocking drains in date 200 per cent of the hydraulic load if extreme cold events that could block all drainage altogether. that approach is taken. Above is an illus-Roofers Proud Of For the rst change, it can be easily incorporated into current designs, and building to that tration of that; see Figure A-2.4.10.4.(5).standard would meet todays code as adopted. The second change would not meet todays code This may be an attempt to mitigate as adopted and should not be incorporated into designs unl this has been formally approved costs of the first change, but while this by the Authority Having Jurisdicon where a project is located. proposedchangewillreducecosts,it may not be a best practice. There have While this is not an exhausve review of roof drainage, it seeks to highlight some of the issues been examples of ice blocking drains in around overow drains, both in current code and upcoming proposed changes. It is important extreme cold events that could block all to consider overows as a required and specied part of the design, as opposed to something drainage altogether.for the contractor compleng the work to gure out. In addion, consideraon should be given For the first change, it can be easily to increased severity of weather events. In my view, besides potenal aesthec consideraons, incorporatedintocurrentdesigns,and there are no drawbacks or negaves from having excess overow drainage capacity installed on buildingtothatstandardwouldmeet the building. That decision may save a building or a life.todayscodeasadopted.Thesecond change would not meet todays code as adopted and should not be incorporated into designs until this has been formally approvedbytheAuthorityHaving Jurisdiction where a project is located.Whilethisisnotanexhaustive reviewofroofdrainage,itseeksto highlightsomeoftheissuesaround overflowdrains,bothincurrentcode andupcomingproposedchanges.It isimportanttoconsideroverflowsas arequiredandspecifiedpartofthe design,asopposedtosomethingfor the contractor completing the work to figureout.Inaddition,consideration shouldbegiventoincreasedseverity of weather events. In my view, besides potential aesthetic considerations, there 604-882-9734 arenodrawbacksornegativesfromrcabc.org for full member details having excess overflow drainage capacity rcabc.org installed on the building. That decision may save a building or a life.30 lROOFINGBClFALL 2024'