Scuppers were originally openings in bulwarks on decks of sailing ships, draining water falling from crashing waves in storms. This kept the water away from deck houses and cabins and storage areas below. Flat roofs have similar challenges. It’s a good idea to install pipe to bring the runoff water gently onto the ground.
Three Ways to Install Water Drains on Flat Roofs
Most flat roofs have raised edges around them to prevent rainwater pouring down in uncontrolled fashion. This makes sense until it pools, and eventually follows cracks and saturates the concrete.
Most residential flat roofs slope gently towards a collection point, which may be at one edge, or at a midpoint somewhere. We discuss three strategies for draining it further with help from scuppers. Your best way to lead the water to the ground depends on the design of your roof.
Drainage Basins Where Water Collects at a Midpoint
The roof should slope towards a collection point. If you retrofit drainage basins these should be where water naturally pools. Advantages of this method include (a) pipes are inside the building and will not freeze, and (b) they are invisible from outside.
However, debris easily collects around the scupper, and blocks it causing potential complications. The only way to prevent this happening is to clear the roof regularly which is a chore. This method is unsuitable if you don’t want a drainpipe in the middle of your house!
Open Scuppers Draining from the Edges of Roofs
If the water pools against a parapet wall, you could make an opening and let it pour out. The leaves should follow the flow and not block it. However, this can cause people inconvenience when walking below. This is not a good solution if you want your walls dry!
Adding Down Spouts to Those Open Scuppers
Therefore, it’s more sensible and practical to connect drains to your scuppers as we show in one example above. This solution is cheaper than drainage basins. However, leaves can block the downspouts and they could freeze in winter!
How to Decide Which Option is Best for You
Speak to Valiant Exteriors if you are anywhere in Calgary. We’ll happily pop by and discuss solutions if you share a few photos first. We provide a full-on service keeping water where it belongs. That’s outside your house so you are dry inside!
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Discharging Flat Roof Water Into Outside Drains (Amzi Smith BY CC 3.0)