Gutter leaking against neighbour's extension - advice, please.

[Coliander]

I recently purchased a semi-detached bungalow. Some years ago, my neighbours built an extension at the rear of the property at the boundary line. When I purchased the property, I noticed that there was some staining down the wall of their extension beneath the gutter stop-end where the guttering was terminated (I assume, when the extension was built).
At the end of last year I had the gutters cleaned which I hoped would alleviate the issue, but today the neighbour has had some employees from a local building firm round inspecting the wall abd taking photos of the staining (seen on video doorbell).

I don't get the opportunity to speak to my neighbours much, i work very long hours and rarely see them. But when I have it has always been friendly.
The neighbour has not mentioned any issues with my guttering causing damp and I assumed that the issue was rectified once I had the gutters cleaned.

I assume it's my responsibility to make sure my gutter doesn't leak onto their property, but what are my rights should this become an expensive fix (assuming the guttering is still leaking?).

See rough image for details.

 

[Coliander]

Staining on wall:

 

[mrrusty]

First, it's a bungalow so it can't be an expensive fix - no scaffolding needed. Second, is your gutter actually leaking or overflowing? - stick a hose pipe in it and test it.

It's quite possible that when it rains hard water is just spilling through the gap between the side of their extension and the end of your gutter. Possible a piece of lead carefully shaped to cover the gap and direct water either into the gutter or on to their roof might help.

If your gutter can't cope with the water coming off your roof, check the down pipes are clear in to the gulley and/or fit a bigger gutter, which on a bungalow is a couple of hours work and not much money.

 

[Diver Fred]

A photo taken outside looking at the gutter/edge of there roof will help.
However a couple of thoughts;
Is the endcap of your gutter complete, fixed properly and the seal intact?
As MrRusty says is there any directing structurework over the junction between the gutter and the neighbours roof? I'd be expecting some leadwork to stop such problems.
Is there space between the end of the gutter and the neighbours roof?
Is there a raised edge in your neighbours roof and does the raised section go under the cant roof?

 

[DiyNutJob]

Take picture/video in rain. Saves all the guessing.

 

[Coliander]

Thanks, all. Decided to pop up and take a closer look/speak to the neighbour instead of spending all afternoon distracted by it.
Turns out there is a very small ~5mm gap between the end of my gutter and the extension wall that is allowing rainwater through. Seems when the extension was built, the builders didn't put anything in place to divert the flow/compensate for this gap.
Neighbour is having the entire extension roof replaced, so wanted to have this issue rectified at the same time. Bit of a relief that It's not an issue with my guttering, just appeared that way due to the pattern on the wall.

 

[freddiemercurystwin]

Always pays to open a dialogue first off when problems arise.

 

[^woody^]

A stop end will slide out 5mm, no problem.

Are you sure it's not related to a joint in the edge capping felt like that one to the right of the photo?