How Do Flat Roofs Drain Water

Increasing the angle of a flat roof will always.

How do flat roofs drain water.

How to fix ponding on a flat roof depends on the cause of the ponding. For larger flat roofs like those used for flats townhouses commercial buildings or schools it s common to have a drain placed inside the roof edge. A flat roof may use interior drains to collect water from the centre of the roof. It may also void your warranty.

Your building and location can help determine which drain will fit your roof needs. Still the function of the two drains is the same. Calculate drains needed. Of course the best designed flat roof has the correct amount of pitch to drain the water off naturally.

This table is based on zurn s roof drain vertical requirement for horizontal roof areas at various rainfall rates table. Unlike other roofing types that are slanted or sloped to allow water to drain automatically flat roofs need a built in drainage system to help remove moisture and debris. The main benefit of inner drains is that the system is hidden from view. Along with the benefits of a flat roof come unique challenges.

Inner roof drains are used on flat roofs and include a low section or channel that collects water and feeds it into a concealed drain that leads to an underground drainage system. The roof is designed to have a gentle slope towards that drain from where the water is piped away from the walls and foundations. These drains are like the drain at the bottom of your shower except that the roof drain has a larger strainer to protect it from debris. For a large roof it is recommended to have drains placed at multiple locations within the area of the roof.

The most critical of these issues is the flat roof drainage systems. Puddles or ponding water is water from rainstorms and snow melts that collects on a flat roof and doesn t drain or evaporate after 48 hours. Internal drains are often placed in low slope roofs when the roof span. The above sizing data is offered as a guide only.

The one challenge with flat roofing is ensuring proper drainage. How water runs off a roof depends on the amount of rainfall and how quickly it needs to drain. However excessive ponding threatens your roof. Water falls on the roof and gravity draws it into the drain and down the.

The scuppers are the openings in the outside walls specifically designed to allow water but not debris to wash off your roof. A low slope roof tilts slightly downhill from its center or from one side so water rolls off to parapet scuppers and down the hopper downspout. The result is the number of drains needed. Take the roof s total square footage and divide by the total square footage handled by one drain.

So if your flat roof is collecting water that doesn t drain or evaporate within 48 hours you will need to fix it. Poor drainage can lead to serious issues with flat roofing from leaks to structural damage. Inner roof drains.