Choosing the right size of gutters and downpipes step 1.
Calculate gutter size uk.
That is how much rain a roof can drain during the most intense rainfall.
L1 l2 selecting gutter size there is no standard rate of rainfall in the uk so for accurate calculations refer to an approved weather authority to get a site specific rainfall level.
The most logical way to choose your gutter size would be according to the area of your roof.
Change the style of gutters to one with a greater capacity.
6 inch 7 960 square feet.
British standard bs en 12056 3.
Geographical location and rainfall intensity maps.
Calculations are based on level gutter capacity as experimentally determined by the national institute of standards and technology nist.
To limit the effects of thermal expansion in gutters 50 ft.
If you ve got a simple gable end roof then it s easy you only need to know two figures one for either slope.
Design area effective area 5 x 10 x 1 29 64 5m run off 64 5m x 0 022 l s per m 1 42 l s from chart 125 x 100 gutter with 76 ΓΈ downpipe appears suitable but check.
Add a fall to the gutters which we recommend you do anyway.
Frequency and positioning of outlets downpipes.
Calculate the square footage by getting up there with a tape measure.
For a typical gutter run up to a maximum of 10m the ratio of gutter lengths is calculated from.
If a roof s various drainage areas call for different size gutters go for the biggest one k style.
Multiply the drainage area by the roof pitch factor and rainfall intensity to find out the adjusted square footage.
That will show how much water a gutter will have to drain.
Downspout sizes must not exceed the bottom width of the gutter.
Move the outlet downpipe from the end of the gutter to the middle.
Calculate the number of outlets per.
Divide the inch per hour watershed of the roof by the 5 minute rainfall intensity.
Determine the rainfall intensity for your location.
Ask gutter suppliers what size gutters will be needed to handle that amount.
5 inch 5 520 square feet.
Gutter ratio l1 l1 l2 where.
Then use the chart below to see what size gutter you need.
Using the 5280 square feet example from step 6 you will choose a gutter size that can handle at least 5280 square feet.
15 m is a practical maximum gutter length to be served by a downspout.
