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Rainfall patterns are changing.

Roof drainage systems have a very important role to play in the drainage of, and watertightness of, every single building in this country. It is particularly important to correctly design and construct parapet, boundary wall, and valley gutters as, if these leak, they will tend to do so INTO the building causing internal damage, which is wholly unacceptable.

The sizing of gutters is dependant upon three main factors :

  • the area of roof to be drained;

  • the position, spacing, and number of rainwater outlets;

  • the allowable space into which the gutter is to be fixed.

The current British Standard for the design of roof drainage is BS EN 12056 Part 3 : 2000. This standard was approved by CEN in October 1999, came into effect in September 2000, and supersedes BS 6367:1983 which has now been withdrawn.

This new standard has a number of key differences from its predecessor in that :

  • there is a change in the way that the rainfall intensity date is presented;

  • there are new methods for the calculation of gutter and outlet capacity;

  • downpipe capacity is restricted to 33% of its total bore.

Although the basic idea of gutter and rainwater pipe sizing is to provide a design that will ensure that the outlets and pipework will be of a sufficient capacity to allow the gutter to flow freely, the whole process can be a very time consuming operation, especially if there are numerous gutter runs to consider.

Upon receipt of your gutter cross-section dimensional information together with the answers to a few additional questions, I can calculate the number of outlets required, and their required spacing to ensure that the flow in the gutter is kept to an allowable level.

Alternatively, it may be that you have an existing design that you would like to have double checked - again, this is not a problem. Upon receipt of all of the required information, existing designs can be checked, with the results confirmed back to you the following working day.

If you would like further information on any of the above services, or if you have any current projects with which you require assistance, please do not hesitate to contact me via the link below.

above is an example of a 'failed' gutter and rainwater pipe calculation.....

above is an example of a 'passed' gutter and rainwater pipe calculation.