b'Drainage Unhealthy Roof Environment DiseasessuchasLegionnaires disease (breathing in bacteria-infect-ed water), West Nile (bitten by an in-fected mosquito) and inhaled mould spores causing allergic reactions can arise from standing water. Sensitive buildings such as hospitals or long-term care homes can be at high risk from these situations. Where build-ing air intakes have compromised fil-ters, the concern can quickly spread through the building.Better Roof Drainage to Avoid Rubber Boots Toavoidtheneedforrubber boots, there are proactive design op-tions to assist in promoting drainage andavoidingwaterconcernsona low-sloped roof.Designingthedrainagesystem to code is always the first step. The NationalPlumbingCode(NPC) ofCanadacontainsroofdrainage capacity calculation procedures, in-cludinghydraulicloadtablesthat enable you to identify drain quan-tity, size and slope required for low-sloped roofs. Roof drainage require-ments, in respect to drain quantity, location and need for control flows or scuppers, are summarized in the NPC under Hydraulic Loads from Roofs or Paved Surfaces.Designloadchecksarecalcula-tionstoconfirmbothhowmuch water the roof deck can hold, as well as the capacity of the hydraulic load on each roof drain. This is essential to prevent a roof collapse by allow-ing a specified drain downtime. The Rooftop standing water. Photo courtesy of W. Allen Partners. structural load needs to be calculated by a structural engineer during new construction and, if not document-12ONTARIO ROOFING NEWSISSUE 4 2023/24 THE ONLY SOURCE FOR PROFESSIONAL ICI ROOFING CONTRACTORS IN ONTARIO ORN'