How Do Flat Roofs Drain Water

However excessive ponding threatens your roof.

How do flat roofs drain water.

Of course the best designed flat roof has the correct amount of pitch to drain the water off naturally. The roof is designed to have a gentle slope towards that drain from where the water is piped away from the walls and foundations. For a large roof it is recommended to have drains placed at multiple locations within the area of the roof. Inner roof drains.

Water falls on the roof and gravity draws it into the drain and down the. 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. Poor drainage can lead to serious issues with flat roofing from leaks to structural damage. 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.

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. Take the roof s total square footage and divide by the total square footage handled by one drain. Flat roofs by their very nature will collect some water when it rains. Calculate drains needed.

It may also void your warranty. Increasing the angle of a flat roof will always. This table is based on zurn s roof drain vertical requirement for horizontal roof areas at various rainfall rates table. The one challenge with flat roofing is ensuring proper drainage.

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. Still the function of the two drains is the same. 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 drainage system of any roof can be located at the edge or in the middle of the roof.

So if your flat roof is collecting water that doesn t drain or evaporate within 48 hours you will need to fix it. The water pools after days or hours of steady precipitation due to a variety of causes such as a clogged drain or structural issues that inhibit drainage. Along with the benefits of a flat roof come unique challenges. Internal drains are often placed in low slope roofs when the roof span.

A flat roof may use interior drains to collect water from the centre of the roof. How to fix ponding on a flat roof depends on the cause of the ponding. The scuppers are the openings in the outside walls specifically designed to allow water but not debris to wash off your roof. How water runs off a roof depends on the amount of rainfall and how quickly it needs to drain.

The above sizing data is offered as a guide only. The result is the number of drains needed. The main benefit of inner drains is that the system is hidden from view.