I have a section of guttering next to a concave corner where two sections of roof meet, where water runs down the side of the house.

View from ground

After having the guttering looked at and still leaking, I've gone up and had a look myself, and found that the cause of the problem is actually water running down the channel between the two roof surfaces, which looks to me too short, so it dribbles onto the board at the end, then down a gap between the guttering and the house (and possibly back under the tiles too?).

I've checked this with a small jug of water, and that does seem to be exactly what happens - path of the water shown by the red arrow.

enter image description here

So it looks to me like the correct fix would be an extension to the grey trim or lining structure in the centre of the channel, so that it extends far enough that water runs from it directly into the guttering.

My questions though:

  • am I correct in thinking the channel liner/trim (afraid I dont know the correct term) is too short and shouldn't be like that?
  • should that gap exist between the gutter and the roof?
  • whats the best way of fixing this, and is it something I can do myself*?

*For context, I'm reasonably proficient at basic DIY, but have never done any roofing. I'm comfortable enough up the ladder as long as its only basic manipulations required

Many thanks

  • Yes, the metal (channel) from the sloping roof seems too short, but I don't think that is the main cause, rather, I think the water has got to the backside of flashing and spilled from behind the gutter to below. A deeper gutter may help to alleviate the problem.
    – r13
    Dec 12, 2021 at 18:47

1 Answer 1


The grey flashing is referred to as valley flashing, and is supposed to extend past the fascia for the full width of the flashing. (The fascia is the vertical board that meets the roof deck.)

Your roof looks to be some sort of stone or tile, so you’ll want a long lasting repair. I would suggest 16 ounce copper, since it’s easy to bend and you don’t need enough for the cost to matter.

Put a fold into it (over the edge of a board is fine, perhaps with a bit of tapping with a hammer), and slide it up under the existing flashing. Note the width you need on each side, so the fold won’t be in the middle. Valley flashing can be in the shape of a V, or like yours with the center ridge, which is called “W” flashing. Note that the extension you slide under it doesn’t need the center ridge.

I would trim the edge with metal shears so it overhangs the gutter.

  • Thanks, thats very useful, I'll give that a go
    – Abort
    Dec 13, 2021 at 22:24

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