Can anyone tell me if there is an appropriate BS, or failing that just
a standard recommendation, for how many downpipes a given run of
guttering needs? I used to have a 40' run of roof with a downpipe at
each end of it, but following an extension I now have a single
downpipe at one end of a 60' run of roof, and the builder assures me
that is sufficient to cope with the amount of rainwater the complete
roof generates. For clarification, the roof has an approx. 30 degree
angle and is roughly 20' of roof, from gutter edge to ridge tile (or
1200 square feet of roof for a single standard downpipe which feeds
into a soakaway in the garden rather than a main drain).
thanks in advance
Many thanks for that. I've read it, several times, and the relevant
bit appears to be on page 41. I'm damned if I can work it out though -
the chart shows with an angle of 30 degree you should multiply the
roof area by 1.29, which gives me a rough effective roof area of 140
sq. m. The chart only goes up to 103 sq. m.!
On Wed, 08 Aug 2007 20:09:15 GMT, a particular chimpanzee, nullified
The factor is only if you've measured the plan area. Assuming your
20' from ridge to eaves is measured on the slope, you don't need to
multiply it by any factors.
One can use the chart to work out how big your gutters need to be and
how far apart your downpipes need to be. So in your case, with a
6.10m length of roof, a 100mm gutter and a 63mm downpipe could drain
an effective run of (37m^2 / 6.10m =) 6.07m. In other words, you
would need a downpipe every ~6m.
There are the other provisos that the distance from a stop end to the
downpipe shouldn't be more than 50x the gutter depth, ie. 50 x 50mm 2.5m for a 100mm gutter, and that there shouldn't be more than 100x
the gutter depth between downpipes, ie. 100 x 50mm = 5.0m.
The guidance is for basic gutters. Proprietary makes will have their
own flow rates.
"If no-one on the internet wants a piece of this,
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.