As a follow up to a recent Technical Bulletin (11-13) We would like to offer some additional options for
flashing steep drain sumps. Sika Roofing promotes the proper roofing practice of creating sufficiently sized
sumps at all roof drains. A proper sump will help direct water to the drain, expedite removal and minimize
ponding. Sika- Roofing offers prefabricated polyisocyanurate drain sumps to simplify this application.
Flashing Steep Drain Sumps
Sika Roofing would like to offer another method for flashing steeply sumped drains. This method involves creating a slight cone shape out of the membrane. Typically the roof drains are flashed with Sarnafil G410 or Sikaplan Adhered. When Sarnafil S327 or Sikaplan Fastened is used in the field of the roof, they may also be used in the drains.
Using a Cone Flashing Detail
This cone flashing detail will result in a seam going through the drain clamping ring. Traditionally,
positioning a seam through a drain clamping ring has not been allowed. With this detail the seam must be
completely welded on the front and back side. This will prevent water from entering the roofing system
through the seam in the event of a drain backup.
Click here to download Technical Bulletin 15-10 This Flashing Deep Sump Drains PDF includes a great step by step pictorial and drawings showing how to build a funnel for a step drain sump detail.