b'TECHNICAL & RESEARCHP roperdetailingofroofpene- system. As part of that system, the primary andthese examples of incorrect tapering and flash-trationsisavitalpartofeveryoverflowdrainsperformindependentlyfroming, there are several issues:completed roofing assembly. Anyeachother.TheprimarydrainisgenerallyTheslope is greater than 2 in 12. penetration through a low-slopelocated at a low point of the roof area and is inHowever, there should not be any verti-roofassemblycouldrepresentplane with or set lower than the roof membranecal transitions. Instead, the sump should potential failure points and leaksplane so as to collect the vast majority of water.have gradual slope on all four sides. during the life cycle of the roof. Whether theThe overflow drains are generally set slightlyThere are field membrane splices closer project is new constructionorreroofing, theabove the roof plane as required by local rain- than 9 in. (225 mm) to the drain clamp-roofmanufacturersanddesignprofessionalsfall records, building codes, and environmentaling ring. Field splices are generally not developveryspecificdetailingprocedurestorequirements. permitted to be within 12 in. (300 mm) reducethepossibilityofbreachesoccurring.Insulationdrainsumpsinvolveaddition- of the clamping ring per the roof man-The roofing professionals who undertake thealconsiderations.Thetaperedsumpshouldufacturer specifications; each manufac-project must be capable of meeting the expec- have a four-sided, gradual slope (Fig. 1), andturer may have slightly different crite-tationsoftheowner,themanufacturer,andthe tapered insulation the design team. The roofing installation crewwithin the drain sump should be well trained and experienced in theshould not reduce the roof manufacturers recommended installationminimumR-value techniques as well as the architects and build- thicknessoftheroof ing enclosure consultants design details.insulationbymore Asmentionedinthefirstarticleofthisthan1in.(25mm). series, the intent of this series of articles is not toForinstance,section explain design requirements but rather to pro- 402.2.1.2 of the 2021 vide a roofing 101 narrative on best practices.InternationalEnergy To that end, this article describes selected issuesConservationCode 1related to detailing roof penetrations and theindicatesthatthe technical aspects of flashing related to drainageminimumthickness in the thermoplastic roof system; the article isofabove-deckroof not intended to provide technical specificationsinsulationatitslow-for design issues such as proper sizing, water- est point, gutter edge, flow, head of water, or drain locations.roof drain or scupper, shall not be less than ROOF DRAINS 1 in. (25 mm).Roof drains and overflow drains are amongFigures2and3 the most critical components of any internallyillustrateincorrect drained roof assembly because they are respon- tapering and flashing siblefortheremovalofwaterfromtheroofof the drain sump. InFigure 1. Diagram of a four-sided tapered drain sump.6 www.mrca.orgMidwest Roofer18'