Minimum Roof Area Before I Need Roof Drainage

Adding a roof can create drainage problems if the roof pitch is too shallow.

Minimum roof area before i need roof drainage.

Rainfall intensities vary throughout new zealand and are often very high. 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. 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. 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.

A good rule to follow is to provide two roof drains for a total roof area less than 10 000 square feet. It s easier to see how this works with a real world example. Calculate total roof area. 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.

Once the drainage system is determined the designer must ensure positive drainage by correctly positioning the roof drains. Increasing the angle of a flat roof will always increase the speed of water movement across the surface. Determine leader or pipe size. Roof drainage systems need to be designed to cope with the rainfall intensities for the specific building location.

Minimum roof pitch the minimum pitch for a roof is 1 4 12 which translates to 1 4 inch rise to 12 inches of run. 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. An additional roof drain should be added for each 10 000 square foot area. Drainage design specific to location.

For a large roof it is recommended to have drains placed at multiple locations within the area of the roof. Evidently there are set standards for the different kinds of roof slopes. Determining the exact roof area and the number of drains is precise work so it requires coordination with the building s architect. Walls that drain onto a lower storey roof can increase the effective roof area by around 50.