Canopy Gutter Design Considerations

Gutter End Assembly Axonometric

Canopy gutters often become a hot potato in terms of who owns them – handed off between trades because of their unique challenges: They can leak, clog, and they require regular maintenance for proper long term operation. Over the years, we have found the following considerations to be most important when designing a gutter from the start.

1. When possible, consider design strategies that don’t require a gutter.
While a water management system is a critical component of a canopy, they are often difficult to work into the minimal aesthetic design of many canopies – especially minimal, all-glass ones. Additionally, the downspouts are directly in view below the canopy. For canopies over city sidewalks, a gutter is a necessary evil. But canopies that completely extend over a directional entrance can sometimes be designed to shed the water off to one side, and onto adjacent landscaping, which is specifically designed to handle the force and volume of the water runoff.

We have seen many designs with a call-out for diverter strips on the edge of the glass to channel the water in a specific direction. However, diverter strips can be another eyesore, and can retain dirt and debris that would otherwise naturally run off the canopy glass. To replace the functionality of diverter strips, we recommend handling the direction of the runoff through slope, sometimes even designing the glass to slope in two directions. This can be done with minimal tweaks to the plane of the glass, often imperceptible to the viewer.

2. A one piece design works best
Gutters have a reputation for leaking. This is often due to two poor design choices: First, gutters are often constructed with steel or aluminum, and then lined with a thin stainless, aluminum, or even membrane material. The joints between the two materials become difficult to seal, and the liner is often installed and/or manufactured by a different team than the gutter. Second, since gutter scuppers can become clogged if not properly sized or maintained, the standing water will find its way through the weakest joints.

We always recommend a one-piece, welded stainless steel gutter design. It is completely fabricated in a shop with consistent quality controls, and designed to be impermeable. Installation is simply about anchoring, with no weathersealing component.

3. Don’t run the downspouts through the exterior cladding and inside the building

The desire to eliminate the aesthetics of a downspout, and the liability of spilling water on the sidewalk leads many designers to propose a downspout system that runs through the curtain wall system and inside the building. We can’t recommend against this strategy strongly enough. Whenever possible, it is important not to penetrate the air/water barrier of the exterior cladding system. The problems that arise include thermal transfer, water intrusion, freezing within the system, and problems with identifying clogged pipes somewhere in the concealed run. For these reasons, we recommend stainless pipes, either round or rectangular, that provide the most attractive material, while keeping outdoor water outdoors. From there, an drain system should be designed to manage water runoff below grade.