Serving WA • OR • ID • MT • AK — MG products also in Canada
Call us: 360-703-2960
Resources • Drainage

How to Choose the Right Roof Drainage Product

Ponding water shortens membrane life, voids warranties, and generates callbacks. Here's a practical framework for picking the right fix.

Home / Resources / Article

MG Building Supply • Resources

Start with why the water is standing

Every ponding problem has a cause: structural deflection, inadequate slope in the original design, a curb or penetration interrupting flow, or a clogged/undersized drain. Match the fix to the cause — not the symptom.

The main tool categories

1. Drains and scuppers

If water has nowhere to go, no slope product will save you. Confirm drains are clear, sized correctly, and positioned at low points. Prefabricated drain and scupper flashings (like those from Acme Cone) make retrofit tie-ins cleaner and faster.

2. Crickets and saddles

Behind curbs, skylights, and HVAC units, a cricket splits and redirects flow around the obstruction. Traditional builds use tapered insulation under the membrane — effective, but it means opening the roof system.

3. Tapered insulation systems

The right answer for large-area slope correction on reroofs, but heavy on design, lead time, and cost for a spot problem.

4. Pourable slope compounds

For localized ponding at curbs, a semi-self-leveling compound like Curb Slope creates positive slope from the curb to the field of the roof without tearing into the system. It's the service-call answer: fast application, fast return to service, no tear-off.

A simple decision path

  1. Is the drain working? Clear or upgrade it first.
  2. Is the ponding at a curb or penetration? Spot-fix with a pourable slope compound or a prefab cricket.
  3. Is the ponding field-wide? You're in tapered-insulation territory; plan it into the reroof.
  4. Is water actively leaking while you decide? Control it now with Flash Dam, then fix the drainage.

Don't forget the details

Whatever moves the water, the terminations decide whether it stays out. Membrane-clad metal (like Clad Rex laminated drip edge and gravel stop) and hand-welded prefab flashings keep edges and penetrations watertight where drainage changes direction.

Not sure which category your roof falls into? That's literally our job — send us the details.

Want this answered for your specific roof?

Send us the details — deck, membrane, and the problem. We'll match a product to it.

Ask MG