Rainwater Calculations
Ask our experts

Why do I Need a Rainwater Calculation

Regulations require that rainwater is drained from a roof within a certain time to ensure that the roof does not contain more water than the structure can withstand.


The requirements differ depending on the location of the building, the roof pitch and the overall roof area.


It would be easy with roof drainage outlets to either under specify – which could damage to the building – or over-specify - using unnecessary installation time and money.

Our Service

In order to prevent damage to the building from rainwater, Fixfast can provide you with a rainwater calculation.


Fixfast roof outlets have all been tested for their flow rates and the technical department can carry out rainwater flow rate calculations that will provide you with a scheme in accordance with the UK design standard BS EN 12056 : 3-2000.


The service is free of charge – start the request here.

How do I arrange a calculation for my project?

Simple. Just give us a call or fill out the request form below. A friendly member of our team will be in touch within 24 hours (our offices are open Monday – Friday). Depending on the complexity of your project, the final calculations will be handed over to you within 48 hours, and a member of the technical team will be available to discuss the findings in detail if needed.

Request now
rainwater calculations