dormer runoff leading to lower gutter overflow

24 Aug 2005
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United Kingdom
Hi, rainwater coming from the dormer downpipe rockets down the roof (as in red arrow on pic) and when it hits the main lower roof gutter it tends to overflow causing a drip/torrent depending on how heavy the rain is.

Tends to also soak wooden fascia and splash onto ground floor sill so keen to sort it before winter.

No gutter blockage or downpipe blockage observed (on a ladder in heavy rain). Not the overflow from water tanks etc. Just hits the gutter and some water spins over the sides. Looks like its been happening for years.

Thought of somehow cutting out attaching an extra piece of gutter either side of the main gutter where the dormer drains to to provide deeper gutter for water to flow into. If I did this whats the best way to attach the new deeper sides to original gutter?

any other ideas?

p.s. guttering is older Marley deepflow which seems to be compatible with newer version of Marley deepflow.

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Hi If the gutter on dormer were to be extended on both sides to withing say 100 mm of roof (level through out ) is would reduce discharge by 50 percent at existing point of flow. This may well be sufficient to cure the problem?
I think I'd try a second downpipe on the other end of the dormer gutter. Would mean lowering the L/H end slightly to get an even flow to both pipes.
Why not fit an additional rwp to the other side of the dormer, that should half the amount of rainfall and prob solve the problem.
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the idea of adapting the dormer pipe is good but its a nightmare to get access to the dormer unless I go out the window tied to a rope!

The roof is deceptively long and I havent seen anyone get a roof ladder to reach from the lower gutter onto the ridge of one of these roofs yet.

Dont have a roof ladder anyway but guess I could try to hire one
I think you should do it but obviously not at the expense of killing yourself! :LOL: Fitting an oversized section of guttering just in that area is a little adhoc, I suppose you could just stick something in the gutter to stop the water splashing over the edge of the gutter or fix something in the end of the pipe like a gauze to stop the water pouring out quite so much. Or are you saying that the gutter in that location does not have the capacity and is overflowing rather than splashing out, as it were!
You can get access to the gutterline between the problem area and the main down pipe :?: Get a few pieces of sheet metal bent to 90 degrees and tuck one under a row of tiles then .... "cascade" the water from one down to the next to the area of themain down pipe :idea: Looks like you`d get 5 in there are 5 courses to tuck under from front of dormer to eaves.
the gutter capacity is fine. I checked this during during heavy rain. Its just how the water flows into the lower gutter from the dormer. Part of the problem is that the wavy nature of the tiles combines to form a channel that the water rockets down to the lower gutter. So dispersing the water flow in a way that doesnt block any pipes sound like a good idea that can be reversed if it doesnt do the trick. I wonder if I can get hold of a small piece of lead flashing as have no idea where to get a small bit of metal sheet.
Couldn`t see the wavy tiles :oops: Lead would be good . But from a scrappy or a builder. They only sell the stuff in rolls now..well down here they do :evil:
missus replaced our pic with neighbours place as their estate agent took a better pic....sorry I didnt comment as feared it would complicate things. Our place is identical except we have double pantile slates. These prob cause half the prob as the channel the water straight down.

I may have got hold of some lead so will report back when I get a chance to get up onto the roof and try some of the suggested ideas.
I'm glad you told us what you've actually got on your roof, because it saves me the trouble of making my next suggestion which would only really work with a flat tile. I believe Nige's 'deflector' method would also be less efficient with pantiles, as well as being a challenging piece of sheet-metal work for an amateur.
Go on! Man up and get the rope out. It doesn't look like it's that much of a stretch from the window to the end of the gutter.

PS. Don't tie the other end of the rope to a radiator unless you're intending to start posting in the plumbing forum.
:LOL: aint gonna work. specialy if marley bold roll :oops: Seriously, take the gutter right off the dormer. Just make sure you close windows in stormy weather ;)

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