Flat Roof Rainwater Management

Not all flat roofs are created equal. We did not want to risk waterproofing properties of ours by creating back scoopers to direct rainwater into the downspouts. Instead, we went with the open concept by eliminating back parapets and letting the rainwater pour into the conventional gutter system and then channeled into the underground drain. The number and size of the downspouts were calculated based on the roof’s area and pitch. Here is a closer look at the Passive House roof construction.

Helpful rainwater draining considerations

Unfortunately, periodical gutter clogging from nearby maple trees made rainwater spill over the gutters during a hard rain. After unsuccessfully trying out all available and more trivial solutions, I came across the downspout extension by InvisaFlow. Instead of blocking leaves and any tree debris at the downspout entry points (our main reason for clogging), it lets it go through downspouts freely and has a catch-all filter at the bottom. This allows easy access for occasional cleaning and saves me from unnecessary trips to the roof. It also keeps the gutters relatively clean.