Choosing the “Best Drain” for a flat roof depends on the design of a roof.
There are three types of draining systems found for flat roofs
- Internal Drains – These are drains on the inside of a roof that has pipes connected to lead the water out away from the building. Inner drains are common for large commercial roofs where the pitch slants towards the center of the roof where a drain is.
- Scuppers – These are drains on the perimeter of a flat roof. Scuppers are useful when a commercial roof is slanted towards the outside edge, and a parapet wall is preventing to have a drain. Then a scupper is installed through the wall for draining the water off. Sometimes scuppers are installed in conjunction with an internal drain. The scupper then acts as an emergency drain in the event the internal drain gets clogged, the water can spill over into a scupper.
- Gutters – Gutters are standard on residential and metal roofs. When a flat roof slants into one direction, then a gutter is installed at the end of the roof to remove the water to a downspout and leader where it disperses on the ground.
There are several factors that need to be considered when planning to install internal drains:
- Positioning of the internal drain – internal drain strainers can clog up with debris causing the water to back up and flood a huge area of the roof. When this happens, there should not be skylights, bathroom vents, or any other low profile objects near the drain. When a drain is clogged due to debris, it could cause a pool of water sometimes two feet deep. Water will then spill over into skylights and vents causing damage inside the structure.
When re-roofing over an old roof, it is important to re-design the drains so they would function better. Although drains are the most important part of a flat roof, it is the most overlooked object.
A well-designed drain system ensures a long-lasting roof with low maintenance
More articles on roof drains
Flat roof drains are the most overlooked object, yet it is the essential part of a flat roof. Watch videos and read more on the following articles.
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