CRM offers gutter and roof outlet evaluation to BSEN12056-3:2000. The type of evaluation is tailored to a client's needs, from a simple check on capacity to a complete design service. The simple evaluation typically requires the client to provide the details of the roof area and proposed gutter system. CRM evaluate the system and the client is sent an output sheet, showing the system capacity and whether it conforms to the BS requirements, along with a letter explaining the various parameters. If the system lacks capacity, CRM would normally discuss the matter with the client and propose alterations to make the system work. The evaluation can be presented in a form to pass on to a client or architect. The full design service differs in that the client provides CRM a roof area and any constraints or preferences and CRM find the most efficient system to use. Various outlet sizes, gutter sizes and outlet positions are tried until an optimum solution is found. This can reduce the material requirement considerably, leading to a more profitable installation. It can also be used to achieve a certain outcome, e.g. minimum downpipes.

An example calculation output sheet is shown below: