Rainwater discharging onto pitched ground floor roof - skipping guttering

r_c · 6 Oct 2019

I am not in the building trade, so please excuse my lack of knowledge/terminology.

One of the rainwater downpipes from our roof is discharging onto the pitched roof of our ground floor extension. Our neighbour recently told us that this rainwater is actually coming so fast that it misses the guttering on the first floor roof and splashes over it.

The post and photo here seem similar to my situation:
https://diy.stackexchange.com/questions/71585/how-to-prevent-heavy-rainwater-from-jumping-the-gutter

That seems to be an American house. In my case our rainwater pipes are FloPlast 68mm round and our roof tiles are Marley concrete plain roof tiles.

I am not sure what to do. I like the solution suggested on StackExchange, but my rainwater pipes are round and I do not know how I would secure the pipe that runs down the pitched roof. Is there a product in the UK to secure a round pipe like this to roof tiles?

Another idea, suggested here (for a different problem), is to make L brackets with lead as a way of slowing down the water.

I am not sure what to do here, or whether I speak to a roofer or a plumber.

dishman · 6 Oct 2019

Can you angle the spout to that the water takes a different route down the roof fall?

FrodoOne · 6 Oct 2019

r_c said:
One of the rainwater downpipes from our roof is discharging onto the pitched roof of our ground floor extension. Our neighbour recently told us that this rainwater is actually coming so fast that it misses the guttering on the first floor roof and splashes over it.

I am not sure what to do here, or whether I speak to a roofer or a plumber.

A photo of your actual situation would help others discuss your situation.

However, I suggest that you look up images of "downpipe spreader"
Here you will find many illustrations of ways to minimize your problem.
(e. g. https://www.metalroofing.org.nz/files/downpipe-spreader)

(You need to speak to a plumber.)

23vc · 6 Oct 2019

Run the downpipe down the roof and into the gutter, angled in the direction of the outlet

bobasd · 6 Oct 2019

OP, yes, a photo of your roof is needed.

FrodoOne, thanks for that, i'd never heard of it before - slightly off page but i also picked up info on here or google about a very useful item:
a gutter divertor aka a rainwater gutter divertor.

r_c · 6 Oct 2019

Thank you all for you replies.

It is quite hard to take a phot of the area, but I hope this drawing helps show the problem. The water from the roof's gutter is discharged onto the ground floor extension's roof. As it comes down that lower roof it can have so much speed that it can jump the lower roof's gutter.

20191006_130351 (1)

r_c
6 Oct 2019

dishman said:
Can you angle the spout to that the water takes a different route down the roof fall?

This has been suggested. But I do worry that having water running across roof tiles at an angle may cause unintended consequences. However, I'm not in the trade, so I don't know much about roof tiles and could by worrying about nothing.

23vc said:
Run the downpipe down the roof and into the gutter, angled in the direction of the outlet

I would like to do this. but how do you secure the downpipe to the lower roof? I am worried that the downpie resting on the roof will be pushed around by the wind.

FrodoOne said:
However, I suggest that you look up images of "downpipe spreader"

I like the sound of this.

stuart45 · 6 Oct 2019

23vc said:
Run the downpipe down the roof and into the gutter, angled in the direction of the outlet

I had this problem on a job I'm re-pointing in lime. The water was too much for the gutter to handle, so I've put a deep flow gutter in. It was causing damp problems inside.

23vc · 6 Oct 2019

r_c said:
how do you secure the downpipe to the lower roof?

Wire around a tile batten, out under the tile, looped round the pipe. Need to do one myself soon as got the same issue unless someone knows where you can buy one of those spreader thingies.

Leofric · 6 Oct 2019

dishman said:
Can you angle the spout to that the water takes a different route down the roof fall?

Yes, that is often done I think.
p.s.While replying, there were some photos posted on here not long ago showing the sort of situation with rwps from dormers with the outlets pointing straight down the pitched roof where I commented (rather sarcastically ) about rainwater shooting straight over the gutter.
At least angling the discharge as you suggest would help.

^woody^ · 7 Oct 2019

Its a common and standard arrangement. There should be a shoe or a small angled extension and then a sideways shoe to slow down the flow.

It it's flowing over the bottom gutter then it's a problem with thea gutter or eaves tiles, and not the downpipe.

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Rainwater discharging onto pitched ground floor roof - skipping guttering

Leofric

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