Rainwater goods usually referred to as guttering and fall pipes are often as fundamental to keeping a building watertight as the roof coverings.
The purpose of the rainwater goods is to provide a safe and watertight passage for water, collected by a roof slope or elevations, to ground level. Once at ground level, the water can then be discharged as appropriate by a surface water drainage system.
Gutters and fall pipes can be made from an array of materials, importantly, such products should be correctly sized for the roof area that they are designed to accept water from. Further, such products should be in keeping the with the nature of the building to which they are attached.
Guttering and drainage, like other building works, is covered by a British Standard. For reference, this standard is BS EN 12056:3-2000 which supersedes BS6367: 1983 “Code of practice for drainage of roofs and paved areas”
our preferred suppliers
Working out the guttering required
Firstly, when considering rainwater goods it is critical that the effective roof area, from which water will discharge, be calculated.
Simply, the calculation, for a typical roof surface, can be achieved as follows:
AE (m2) = Length (m) x Width (m) x Height / 2
Clearly, more complex roof areas will need alternative calculations.
Once the roof area has been determined, it is important to understand the flow rate before the appropriate gutter can be selected.
Again, a simple equation can be applied:
Flow rate (litres/second) = Effective Area x Rainfall Intensity.
Further, to determine the size of guttering required the number of outlets along the run will need to be considered. Often, due to the unpredictability of the weather, it is best to consider over specifying any rainwater system.
At GNR, we always take into account that a larger gutter, especially on refurbishment projects, is necessary. More so, consideration is always given to the number of outlets, position and frequency of hopper heads and the fall of the guttering.
Where practicable, it is our intention to provide the following.
- The largest gutter possible to suit the style and nature of the property without it looking out of character.
- The greatest number of fall pipes along a run. Again, we are sometimes confined by the number of drainage channels at ground level.
- The largest diameter of fall pipe, again it is important to us that it is in keeping with the nature of the building.
- Some sort of fail-safe option, often, we like to design in hoppers with overflows or lead details from outlets that are designed to alert property owners to blockages before they become an issue.
The nature of our business means that many of the projects undertaken by us involve listed or historic buildings across Yorkshire. Therefore, the nature of the rainwater goods that we deal with is eclectic and by no means limited to the information presented on our site.