Roof Drain Scupper Sizing

The first step in sizing a roof drain is to calculate the surface area of the roof that the drains will be covering as well as the average hourly rainfall rate at the building location.

Roof drain scupper sizing.

Codes have proven to be adequate in sizing roof drains and interior storm water systems for over 70 years. To convert this roof area to an area for use with table a101 2 do this. 1 4 in ft slope building storm drain 2 500 4 x 7 2 9 375 sq ft 4 500 sq ft. Scuppers shall not have an opening dimension of less than 4 inches.

The only unconditional guideline for scupper sizing provided by the code is that scupper openings shall be not less than 4 inches 102 mm in height and have a width that is equal to or greater than the circumference of a roof drain sized for the same roof area so we can at least be certain that round scuppers can t have a diameter of. Calculate drains needed. From table a101 2 a 12 inch wide weir with a. Sizing a roof water drain.

Section 1503 4 2 scuppers when scuppers are used for secondary emergency overflow roof drainage the quantity size location and inlet elevation of the scuppers shall be sized to prevent the depth of ponding water from exceeding that for which the roof was designed as determined by section 1611 1. Enter table a101 2 to find a length and head that will carry 4 500 sq ft or more. Lack of sufficient secondary emergency roof drains systems and lack of scupper drains in the parapets. Roof drain but then states the flow rate in the storm drain.

Take the roof s total square footage and divide by the total square footage handled by one drain. The result is the number of drains needed. Click the table headings to sort by that column. The sizing of roof drains must be large enough to quickly carry away all water entering the roof drains.

These drains are distinguished by having higher rims. As we will see in steps 3 4 the size of the roof drain lines is dependent on the square feet of the roof area being served by each roof drain. Product name manufacturer color bolt hole style lip to lip bolt to bolt 180 bolt to bolt bolt holes type of bolt used material. Each scupper is draining 2 500 sq ft of roof area.

The full flow capacity of a drain is not realized until the water reaches approximately 2 5 above the inlet in a four inch drain and 3 5 in a six inch drain. In addition to the primary roof drains there will also be overflow drains which are used for redundancy and sized in the same manner. The above sizing data is offered as a guide only.