Gutter design issue

[leen...]

Hi All,

We have 2 small dormers and the guttering for these empty out on to the roof below. Essentially they have a down-pipe with a 90 degree elbow on down to the roof below. The 90 degree is angled to be about 45 degrees to the roof tiles below to try and balance spreading the water across the roof with not squirting it under the roof tiles.

In general, this work fine but if it is chucking it down, the force of the water coming out of this creates a "jet" of water on the lower roof which then over shoots the lower gutter.

Where this happens, there is no easy way of putting a down-pipe to the ground (hence why it was done this way). The only other option I can think of was to run down-pipe from the 90 degree elbow to somewhere where I can get to a down-pipe to the ground. I think this would look pretty ugly - anyone have any other ideas?

Thanks

Lee.

[nothanks]

Small vertical plates attached to the existing gutter to stop/catch the overshoot, or a diverter to slow-down the flow and point it in a slightly different direction.

[John Rumm]

Assuming it's directing water onto the tiles from above and not squirting at the sides of them, I would change the 90 deg to a 45, so the jet of water has less "lift" when running fast.

Overshoots and in simply never hits the roof at all and flies past the gutter, or gets into the gutter, but just overloads it and spills over the side?

Overfilling could possibly be fixed by changing to a length of high capacity gutter.

When I did the loft conversion at my previous place, I had a similar problem - the down spout was not that far back from the gutter. With heavy rain it would so the same party trick and just direct a jet of water straight off the roof and onto the ground below. Not an ideal photo, but before modification.

I fixed that with a small hood of flashband that I stuck onto the top of the outlet on the top down pipe, that angled the top of the stream of water down toward the tiles.

[Peter Burke]

[e-mail] wrote in news: [e-mail]:

I have done this on an internal corner valley where the corner of the gutter was being overwhelmed despite there being a nearby downpipe.

Using some spare lead I formed a 2" upstand by approx 12" wide that was self supported by folded over tabs at the front and by extending the lead sheet underneath and creating similar tabs on the inside.

It has been highly effective, the 2" was enough to change what had been a ground soaking deluge into a well moderated flow.

John's idea of fanning out the flow a bit sounds sensible too.

[leen...]

It is a very similar situation to the one you in your photo except that the upper outlet points about 45 degree from horizontal so squirts the water a bit along the roof. Also the distance from the outlet to the lower gutter is about a meter. I guess some of the water goes into the gutter but the vast majority just shoots over the gutter.

Where did you put the flashband? Attach it to the outlet somehow? Assume you created a sort of wide flat and not very high spout to broaden the water flow?

[John Rumm]

Yup pretty much... excuse the crudity of the model, but:

If you start with a spout similar to the one on the left, I cut a rectangle of flashband, and stuck it on the top of the spout overhanging the front and sides.

Then cut slits in it along the top in line with the top corners of the spout. That let me fold the front flap down a bit until I got a suitable deflection angle, then fold the sides down in a similar way so that they are now vertical (the cuts allow the folded bits to not be restricted by the bit already stuck to the top).

Then stick those to the sides of the spout. Finally trim off any overhanging bits with a sharp knife.

In low flow situations it does not do anything, but with high flow it deflects the top of the stream of water downward enough hit the roof and also cause the lower part of the stream to fan out a bit. You can experiment a bit with how much you trim off the sides so as not to funnel the stream too tightly.

[Brian Gaff (Sofa]

Somebody needs to design a kind of delayed action tank system for cases like this, so the sort of rain we get nowadays tends to go somewhere while it can leak out slowly once the downpour has passed over. I have a downpipe in my front garden which was Ok just watering the flower bed for may years, but since wi like yesterday, get 33mm of rain in four hours it causes a flood outside my front door! Brian

[Tim Lamb]

In message <kCuPI.753920$ [e-mail], Peter Burke [e-mail] writes

The gutter overshoot experience of my barn roof was that it depended on speed and mass. Basically, the greater volume/mass/velocity of moving water determined whether each individual trickle had enough energy to overshoot the gutter edge.

Spreading the output from the downpipe as suggested should allow the roof to slow the flow and reduce the energy available at the roof margin.

I had to fit a deflector which works well!