Flat Roof Drainage Design

Size horizontal storm drainage piping.

Flat roof drainage design.

So often we find that inner drains are high on the roof causing water to pool around them. A rooftop garden or additional outside living space are the top reasons people choose flat roofs. The one challenge with flat roofing is ensuring proper drainage. Poor drainage can lead to serious issues with flat roofing from leaks to structural damage.

This applies for rain falling vertically or if it falls at an angle when blown by the wind. The 3 most common drain systems of a flat roof flat roofs have unique architectural characteristics that make them desirable in many situations. They are ideal for climates that don t experience large quantities of rain and moisture. It is a requirement of building regulation part h that adequate provision is made for rainwater to be carried from the roof of the building.

The ultimate draining system that will prevent a roof from flooding. Cities based on inches per hour that may fall during a storm of one hour duration and a 100 year return period. 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. Most draining systems on flat roofs have a poor design or are not correctly installed.

Appendix b in the ipc provides rates of rainfall for various u s. From there the flat roof system you choose will determine the materials you apply. Flat roof drains design and installation are very critical. Select number of roof drains and calculate the roof area sloped to each drain.

In the case of flat roofs the catchment area is the same as the footprint area of the roof being drained. Size vertical storm drainage piping. This pooling water can cause further issues with the rubber membrane collecting leaves moss and other debris that causes harm to rubber membranes. Underneath the basics flat roofs are usually constructed with a ceiling nailed to joists which support a deck usually wood in residential construction a vapor barrier insulation and a roof board.