Damp Valley of Nightmares

[rideforever]

Hi. We've had continuing problems with a valley on the roof and a damp wall below it. Many builders have suggested many many different things, we already the parapet hacked off and re-rendered twice (these are old photos) and the fibreglass gulley re-sealed. With little effect.

It is clear to me the roofers who have been up there, some well established and expensive, do not know what the problem is. Several simply refused to quote because they cannot guaranteed anything. Others just made a guess.

We would like to take some stronger action now but don't know how to proceed. This is a weak point on the roof all the water flowing into the channel and then through the roof with a hidden drain that descends on the front of the building.

What can be done to reach 'security' with it ? I would prefer doing a bit more than less and reaching a finish point with the problem.

Hopefully we don't have to refoof the whole thing.

One builder talked of making a lead "bucket" around the hidden drain, but I don't know how that really looks or what specifically he was suggesting.

Thanks for any input.

 

[dishman]

I will caviat my post by saying....I am not a roofer!

Just a home owner with a similar roof!

Although i cannot see how your roof relates to the roof on the other side of the divide.

My focus would be on the downpipe.

We have a similar section of roof albeit with a better design. Where the two gables join, there is a section of depressed lead which acts like a sink. That has the downpipe attached. Water flows into this sunken area and drains though a tiny downpipe hole. The hole is not big an if a few leaves block it...we get a waterfall between the gables. Since I put a good filter on it, this has never happened.

Now.....the downpipe (from this sunken area) runs down and inside the overhanging roof structure for a short section and then emerges underneath and continues to a drain. However I am aware that the downpipe seems to be damaged in the section that is hidden. This is because some rainwater runs down the outside of the downpipe.

Could this be the case with you? Is any of the downpipe hidden within the roof structure? Could there be a small hole?

Furthemore...unlike my roof design (which I though was bad already) yours has a horrible pinch point. This must block very easily. You need to enure you put a filter to stop any chance of backing up etc.

As I said....not a roofer....just a layman with a thought!

 

[rideforever]

Thanks. When you say a filter, I assume you mean a grate.
I agree, when the work is done I think that section of pipe going through the roof structure needs replacing.
It's an awful design, I once pulled out about 5kg of vegetation that was not helped by seagulls nesting on the chimney at the top of the parapet. I have prevented them nesting now with caging, so the problem is reduced.
Plus scaffolding it's a mare and I think we must try to do more to cover all bases. It will be the 4th piece of work done on it.

 

[dishman]

Well.....I can't see where the hole at the bottom of your valley is as the pinch gets so tight. Is there a hole for the downpipe? Where does the water flow?

If there is a hole...I was talking about a wire balloon guard

You bend the bottom bits to fit the hole and it keeps the leaves away....


Furthermore, if the hidden downpipe runs anywhere near to where the damp is appearing....that is further evidence that the downpipe may be the cause...

However, as I said....I cannot see how close the two relate in terms of position.

 

[catlad]

You might be be off getting a lead worker in and renew all the leadwork.

 

[rideforever]

Down at the bottom of that corner is a mess. I would prefer if that corner was all lead not just on the valley floor but rising on all sides, I am not sure if there is a possibility for the lead to completely seal the lower corner, rising up the masonry on the parapet embedded 9inches up on that side, and likewise on the tiles rising up perhaps removing some courses. So in that corner instead of hanging a lead/masonry threshold on one side and a tile/lead threshold on the other and a stupid blind corner where anything can be happening, you just have lead all round like a funnel. And preferably welded together rather than overlapped.
I do happen to know an excellent leadworker.
Doing the lead funnel, plus a new pipe underneath and a basket filter is on the shopping list.

 

[terrypin]

Not sure as I'm viewing the photos on an iPhone so not best quality, have you checked the headlap on the tiles? There seems to be a lot of tile showing, especially in photo 2 it looks like there's about 30-50mm of headlap judging by the amount of tile on show.
As I say, on an iPhone so not easy to judge.

 

[rideforever]

wrt headlap ... nothing seems to be coming through the ceiling, it is the wall that is damp in that corner on both sides. If it was the tiles I would expect discolouration on the ceiling below.
The headlap means the amount of overlap doesn't it ? If that was wrong then the whole roof would be wrong wouldn't it ? The slope of the roofs is quite steep as well.

 

[terrypin]

There's underfelt that is a secondary barrier.

It was just an observation, it looks like there's quite a bit of tile showing. It's probably the way it looks on a small screen.