Running gutter downpipe horizontally over a felt flat roof.

It needs some minimal angle of slope or the thing will fill up with leaves and mud often enough to be a real nuisance. I have no idea what building codes say but you might be better off running a length of wide gauge guttering from the down pipe to wherever the water has to go.

Even short going around the weatherboard bits of pipe at 45 degrees sometimes gum up with bits of fallen roof mortar and leaves so any pipe at a shallower angle & 5m long stands no chance of working for long.

Is there a gutter around the flat roof? My back gutter comes down from the main roof and then empties into one corner of the gutter that runs round all three sides of my porch. The combined output of roof and porch then pours down the drain on the opposite side.

Nick

That is how it is and the flat roof gutter can't cope with the rain in a heavy downpour.

Thanks Martin, that is a very good point.

The pads should be concrete or brick. Ideally, get some 600x600x50 paving slabs and cut them into four. Stand each one on a sand bed. Put some fall on the pipe. Maybe use guttering instead of pipe.

Bill

I wonder where you are located? I'm in "Wet" Yorkshire and we certainly get more than our fair share of rain around here.

What I didn't mention before is that my gutters actually drain two main roofs. We are on a terrace down a steep hill and the downpipes are shared between two houses. The gutter from the house uphill from me drains through a short pipe into the end of my guttering and then all the water comes down the downpipe at the other end. They seem to cope. Could there be some other problem with your system?

Nick

The problem with using a section of gutter is keeping it in place during strong wind. You might want to position some

I think there were originally two separate downpipes and two drains and the builders of the flat roof kitchen extension diverted one into the other and now it can't cope in a heavy downpour.

In message snipped-for-privacy@googlegroups.com, Rednadnerb snipped-for-privacy@hotmail.co.uk> writes

For a 5" pipe I'd put supports every two foot.

Bill

I'd have a gentle slope in the pipe by having stand offs of differing sizes. One tends to get crud from the gutters building up in the horizontal bit otherwise. I used to see a lot of clever ideas, even a second gutter along the edge of the flat roof and the downpipe feeding into that, or course no telling what constitutes flat, since you need a slope or you end up with a roof lake. Brian

In message <spch0v$v5d$ snipped-for-privacy@dont-email.me, "Brian Gaff (Sofa)" snipped-for-privacy@blueyonder.co.uk> writes

Upthread, the OP says the flat roof gutter is overwhelmed in heavy rain. Could the problem be insufficient fall on the new flat roof gutter or downpipe obstruction due to leaf filter etc?