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Before you start
It is the total area of the roof that decides the dimensions of the roof drainage system. The bigger the roof, the more water the system must take care of. It will pay in the long run to be careful when you measure your roof and calculate dimensions. If you have any doubt we are happy to help by telephone or email to pick out all the components you need.
Measure the roof area
There are various types of roof layouts but measure each roof part by multiplying the roof length with the roof width. If the area is less than 50 m² use 100 mm gutters (width – Inside measurement) and 75 mm down pipes (diameter). If the area is between 50-100 m² use 125 mm gutters (width – Inside measurement) and 87 mm down pipes (diameter). If the area is larger than 100 m² there are gutters available from the range at 150 mm (width – Inside measurement) and 100mm down pipes (diameter). If there are different roofs on the same building the largest roof area determines your minimum drainage capacity.
Number of brackets and down pipes
The brackets should be installed at 600 mm centres. The end brackets are mounted 100 mm from the roof edge.
The inclination of the gutter towards the down pipe should be at least 2,5 mm/m. Calculate how many brackets you need for each run (example 10 m/0,6 m +1 = 18 brackets). Each down pipe covers maximum 10 m gutter fall (length of the house). For aesthetic reasons or if the gutter fall exceeds 10 m, place pipes on each corner of the house.
Where to place the down pipes
The pictures below show recommended placement of downpipes for different houses. However these will need to feed into a drainage system on the ground so this should be taken into consideration before positioning down pipes and outlets.
For more tips on how to install your guttering see our install guide.