The six most typical roof types are ‘’Flat’’, “Single,” “Hipped,” “Valley’’, “Double Valley,” and ‘’Single – commercial’’  as seen below.
The calculated roof area is indicated by the grey area. Two computations are necessary for a typical semi-detached or detached house with a “Single” roof design—one for each side. By combining these four modules, more roof spaces can be accommodated.
A calculator will show on your screen after you click the link for the preferred roof design; enter the necessary dimensions and the number of downpipe outlets. Click the Calculate button once this is done. Returning to the calculator boxes will change the size or number of outlets. Click the reset button to start a new calculation or to clear the data you’ve previously entered.

The result will give you a link to follow, that will forward you to the appropriate system to use for your building.

Note that this was estimated using the highest flow rates possible for each system. However, Kalsi Plastics advises using the next largest system or adding an additional downpipe to the system if the flow rate in litres per second approaches the maximum for the specified system.