Roof Drainage Design Guide

Roofs inevitably serve as temporary rainwater reservoirs.

Roof drainage design guide.

Maximum pipe flow. Step by step instructions step 1. Select number of roof drains and calculate the roof area sloped to each drain. Developing the design criteria for a roof drainage plan that will perform with the roofing system to drain the roof is critical priorto the bid process and roof system installation.

The location and degree to which. Slope of the roof. Design assistance services are offered as a courtesy to the roofing design professional and contractors to ensure the project s success. Location of drains 5.

In either case the discharge shall be located so that it is readily visible by building occupants. Secondary or emergency roof drainage is required wherever the buildup of water is detrimental to the roof structure. Type of roof construction 2. To select the proper roof drain the following information must be known.

Safety load requirement 8. Secondary drainage shall be provided through the use of sidewall scuppers or internal roof drains. 2 3 4 5 6 and 8 in. Desired rate of drainage 6.

Roof load requirement 7. Properly designed roof drain must have the following features. First and foremost be sure to comply with all local plumbing codes. Size vertical storm drainage piping.

Rainfall intensity roof catchment area gutter size capacity gutter fall gutter outlets sumps rain heads nozzles downpipe size quantity and placement overflow consideration material. Volume of expected rainfall. Ipc provides four steps to size the roof drains on a building. Calculate total roof area.

The sizing of the roof drainage system must consider all components. In the design and detailing of a roof drainage system consideration must be given to a range of factors such as. Size horizontal storm drainage piping. Determine leader or pipe size.

From there consider the following. The rain storm the flow of rainwater on the roof surface the ability of the roof drain to move the water from the roof to the piping the vertical piping the horizontal piping and the connection to the point of discharge. Inspect the roof surface and roof drains on a regular schedule to find and clear away any debris clogging the drains. Pleasing dome shape with a low profile and adequate free drainage area corrosion resisting dome material effective debris protection overflow drainage to allow drainage during debris build up gravel stop positive flashing clamp seepage control channels.

The greater the slope the less water build up and thus roof load. Calculate the total roof area by multiplying its length by width. 2 3 4 5 6. When selecting a roof drain note.