Minimum Roof Area Before I Need Roof Drainage

Drainage design specific to location.

Minimum roof area before i need roof drainage. Assume you are tasked to size a horizontal roof drain serving 5 000 square feet of roof area on a building located in dallas tx. There are 5 easy steps to figure out how many drains your commercial roofing project will need. Determining the exact roof area and the number of drains is precise work so it requires coordination with the building s architect. Calculate total roof area.

Increasing the angle of a flat roof will always increase the speed of water movement across the surface. Adding a roof can create drainage problems if the roof pitch is too shallow. A good rule to follow is to provide two roof drains for a total roof area less than 10 000 square feet. Roof replacement or roof recover of existing low slope roof coverings shall not be required to meet the minimum design slope requirement of one quarter unit vertical in 12 units horizontal 2 percent slope in section 1507 for roofs that provide positive roof drainage.

Rainfall intensities vary throughout new zealand and are often very high. Calculate the total roof area by multiplying its length by width. The drainage system of any roof can be located at the edge or in the middle of the roof. For a large roof it is recommended to have drains placed at multiple locations within the area of the roof.

A small roof with a shorter length on the other hand will not collect a lot of water within a short period of time and will work just fine with the minimum roof slope for drainage. 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. An additional roof drain should be added for each 10 000 square foot area. Once the drainage system is determined the designer must ensure positive drainage by correctly positioning the roof drains.

It s easier to see how this works with a real world example. Roof drainage systems need to be designed to cope with the rainfall intensities for the specific building location. According to bs 6229 bs 8217 flat roofs should be designed with minimum falls of 1 40 to ensure a finished fall of 1 80 can be achieved allowing for any inaccuracies in the. Determine leader or pipe size.