Flat roofs catch rainwater and snow, but they don’t have the advantages of peaks and valleys to direct moisture away to drainage points. We therefore need another way to remove the water and lead it off safely. We discuss the three main methods to achieve this, before focusing on flat roofs and gutters and sharing a few tips.
The Three Main Ways of Draining Flat Roofs
Flat Roofs with Internal Drains
Flat roofs with drains slope gently towards internal drainage points on their upper surface. Some architects prefer this method, because it contributes to clean building design. However, the drains can block with wind-blown debris out of sight of people on the ground. Down pipes pass through the building structure and may cause damp if they leak.
Flat Roofs and Scuppers
Flat roofs with parapets surrounding them drain through chutes called scuppers penetrating the upper wall. These must be at the lowest point, or points on the gentle slope. They are simple to install, but may give trouble if wind-blown debris blocks them. Scuppers may connect to down pipes that should lead the water safely away.
Flat Roofs and Gutters
Gutters are in many ways the best solution for draining flat roofs that slope directly in a particular direction. Good care needs to be taken with the roof-to-gutter interface though, to avoid drips and leaks. Gutters may also block with wind-blown debris. However, unlike the other two solutions discussed, overflows from stoppages are easily spotted from below.
The Flat Roof and Gutter Interface
Care must be taken to ensure all the water flows off the roof and into the gutter, so there is no splashing that could cause damp down below. The best solution is often a hard fascia partly overlapping the gutter line, although this must be positioned correctly.
We recently assisted a client whose home featured flashing that almost completely covered the gutter. We had to cut away some of this material to get the gutter in the correct position to receive the water, as we show in our picture above.
Check List for Ideal Flat Roof and Gutter Alignment
Make sure the roof slopes gently towards the gutter without any noticeable ridge on the edge. Double check that the gutter brackets and hangars are tightly in position. Ensure the down pipe leader extensions drain the water away from the foundations. Call Valiant Exteriors on (403) 829-1661 if you still have damp problems. We are Calgary’s acknowledged flat roof and gutter experts. We will know what to do.
More Information
Why Proper Roof Drainage Really Matters
Custom Angled Endcaps for Eavestroughs
A Flat Roof Can Be a Challenge to Drain (KVDP BY Public Domain)