Roof Rainwater Drainage Design

Crm offers gutter and roof outlet evaluation to bsen12056 3 2000.

Roof rainwater drainage design.

To assess the suitability of a gutter system to drain the roof of a building the following factors need to be taken into consideration. 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. A typical commercial or multifamily residential building will utilize one of the following types of primary roof drainage. The first provides background information either explaining the basis of the recommendations in bs en 12056 3 or in some cases giving additional data.

To undertake design work the client would typically provide the details of the roof area and proposed gutter system ideally in autocad dwg. These will drain to somewhere near the center of the roof and down through the building to underground storm mains or a detention pond. Drainage design specific to location. The number and position of downpipes.

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 flow characteristics of the gutter system. 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 second part describes in detail the steps that.

The effective roof area to be drained. 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. In the case of flat roofs the catchment area is the same as the footprint area of the roof being drained. Each chapter consists of two parts.

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. 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. This applies for rain falling vertically or if it falls at an angle when blown by the wind. Rainwater drainage is covered by building regulations part h3.

The dimensions of the rainwater drainage system can be calculated by means of this quantity of rainfall to discharge per unit of time. 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. The main benefit of inner drains is that the system is hidden from view. Walls that drain onto a lower storey roof can increase the effective roof area by around 50.

The type of evaluation is tailored to a client s needs from a simple check on capacity to a complete design service. For pitched roofs the catchment area would be the same as the footprint area of the roof being drained for rain falling vertically.