Roof Drainage Design

Select number of roof drains and calculate the roof area sloped to each drain.

Roof drainage design.

Starts with 40 pipes but can drain those pipes into the next 40 pipes and so on. From the very dawn of building construction it has been necessary to incorporate some method of gathering and discharging rainwater from the roof of a structure. A typical commercial or multifamily residential building will utilize one of the following types of primary roof drainage. Drainage solutions watts roof drains provide flexible solutions for specifiers and installers in any commercial roof application.

Commonly used on flat commercial roofs siphonic drains allow for a minimal number of drains and all of the drains can be connected to a single leader. Our exclusive dual functional structural deck flange and combination roof drains streamline specifications saving installation time and labor. Take the roof s total square footage and divide by the total square footage handled by one drain. More attention should be given to the location of a drainage system to avoid future problems.

Please see roof drainage calculations for a detailed answer to your question. For most dwellings you ll find that gutters range in size from approximately 100mm diameter to 150mm diameter assuming gutters with a half round section profile and downpipes range from approximately 60mm diameter to 90mm diameter assuming circular downpipes. Design of eaves gutters box gutters downpipes. Hence this is by far the most common roof drainage situation.

The above sizing data is offered as a guide only. Appendix b in the ipc provides rates of rainfall for various u s. This table is based on zurn s roof drain vertical requirement for horizontal roof areas at various rainfall rates table. Size vertical storm drainage piping.

Cities based on inches per hour that may fall during a storm of one hour duration and a 100 year return period. To design a sloped or flat roof drainage system we need to know the anticipated maximum rainfall rate and the flat or projected roof area. In many cases early structures were designed primarily as a shelter from the rain their very purpose was to redirect rainfall and maintain a particular area. Roof drainage is one of the fundamental considerations of building design.

Flat roof drains scuppers gutters and drainage systems on flat roofs one of the most overlooked items on a flat roof is the draining system. Size horizontal storm drainage piping. I examined several roof drainage calculators and tables to see what they tell us. Suitable for flattish roofs with little or no vertical faces or steep roofs draining to one side of box gutter only or any roof if you are in a hurry and make the necessary allowances for all catchments.

The result is the number of drains needed. These will drain to somewhere near the center of the roof and down through the building to underground storm mains or a detention pond.