Roof Rainwater Drainage Design

The type of evaluation is tailored to a client s needs from a simple check on capacity to a complete design service.

Roof rainwater drainage design.

The dimensions of the rainwater drainage system can be calculated by means of this quantity of rainfall to discharge per unit of time. Drainage design specific to location. This applies for rain falling vertically or if it falls at an angle when blown by the wind. The first provides background information either explaining the basis of the recommendations in bs en 12056 3 or in some cases giving additional data.

When designing a roof consider how rainwater will impact both roof and upper floor walls and how this water will be drained collected and disposed of. A typical commercial or multifamily residential building will utilize one of the following types of primary roof drainage. Walls that drain onto a lower storey roof can increase the effective roof area by around 50. Drainage of flat roofs overflow weirs rainwater pipes and drains inside buildings siphonic systems.

Approved document h makes basic provisions for adequate disposal of rainwater from roofs and paved areas minimising the risk of blockages or leakage and ensuring access is provided for maintenance. Crm offers gutter and roof outlet evaluation to bsen12056 3 2000. According to the chart for 1 8 slope per 12 of pipe for 5 000 square feet of roof area with a 6 per hour of rainfall the required pipe size is 8. The second part describes in detail the steps that.

To assess the suitability of a gutter system to drain the roof of a building the following factors need to be taken into consideration. To size the vertical roof drain for the same parameters 5 000 square feet of room area and 6 per hour of rain consult table 1106 2 figure 3. The flow characteristics of the gutter system. These will drain to somewhere near the center of the roof and down through the building to underground storm mains or a detention pond.

In the case of flat roofs the catchment area is the same as the footprint area of the roof being drained. It is important for architects plumbing engineers and civil engineers to work together to design a system that will properly drain rainwater from a building and site. To undertake design work the client would typically provide the details of the roof area and proposed gutter system ideally in autocad dwg. The quantity of rainwater on a roof surface is determined by the effective roof surface in m to be multiplied by the rain intensity i l min.

The number and position of downpipes. Each chapter consists of two parts. This cpd shows how the choice and specification of the roof structure and its finishes can make a significant impact on the capacity required for surface water drainage. Inner drains are resistant to freezing but can require careful maintenance to prevent problems.

The effective roof area to be drained. Inner roof drains are used on flat roofs and include a low section or channel that collects water and feeds it into a concealed drain that leads to an underground drainage system.