Lead gulley leaks when heavy snow thaws

[noseall]

In this image you can clearly see the eaves lathe disappearing as the lead creeps higher.

This is the left side of the gulley.

• quisquose
• 4 Feb 2013
• 1

The overlap here, about a metre from the end is where the water is getting in after snow. I...

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In the end-on image below, the bottom course of tiles stops at that ridge leaning up the roof. Then look at the next course of tiles above and it is clearly missing a full course between it and the first course

From the end of the gulley

• quisquose
• 4 Feb 2013
• 1

Image from 2012 whilst we were having the ridge tiles rebedded

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[noseall]

[Unfortunately, the builders who did our extension did turn out to be cowboys and it was they who replaced the tiles, not the plumber

Says it all!

The lathes are clearly there, the dopey builders just haven't used them.

 

[quisquose]

Thanks for the comments noseall, very useful.

I think I'll have a look out there sooner rather than later and lift some tiles. The access onto there is quite easy, and there's no mortar under the tiles.

It's a shame that the problem only appears during heavy snow, and everything is fine in torrential rain, rather than the other way round. It'll be a long time before I know if any tweaking is effective.

 

[noseall]

I think I'll have a look out there sooner rather than later and lift some tiles. The access onto there is quite easy, and there's no mortar under the tiles.

Yeah, good plan and take some piccies before removing any tiles.

 

[xfr]

What i would like to see is the first length of lead exposed
no good lead worker would do a job like that.the lead is not dressed tightly into the step,because he new he would split it,so if he has not got the skill to do that.The upstands on the first length will not have been installed properly.
this would usally be cut and burnt.
Thats why there's imho a massive lap,Not needed if done correctly..

 

[quisquose]

Okay, with snow predicted for today I thought I'd better get out there yesterday and lift a few slates.

Here are some piccies.

The first picture is as soon as I got out there. The plastic tie was pushed out from the attic to mark where the water is getting in.

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• quisquose
• 10 Feb 2013
• 1

The second picture is a close up of the area. Remember, this is only happening when very heavy snow thaws. There's no evidence of damp on the top of the ceiling, so the water is finding its way through the leadwork and onto the brickwork which supports the gulley, and then spreads underneath the ceiling above the ceiling paper. About 50ml worth with the last snow.

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• quisquose
• 10 Feb 2013
• 1

The next two pictures show the area with some tiles removed.

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• quisquose
• 10 Feb 2013
• 1

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• quisquose
• 10 Feb 2013
• 1

In the end I removed about 15 tiles, and put about a metre of flashing tape between the top of the lead and the lower batten. This is just a temporary bodge, but I'm curious to see if it works. If it does I'll do something a bit more permanent.

Need some heavy snow now.

 

[noseall]

Condensation

 

[quisquose]

There's no evidence of condensation at all.

 

[datarebal]

There is a small flat area between the bottom of the tiles and the point where the lead is formed into the gutter. water can easily back track here.
It is a poor detail which could be dealt with by insertion of eaves and a cut course of tiles
Also I think the splash lap size is working against you. certainly it should be raked back on the sides rather than a straight cut across the gutter

 

[quisquose]

There is a small flat area between the bottom of the tiles and the point where the lead is formed into the gutter. water can easily back track here.
It is a poor detail which could be dealt with by insertion of eaves and a cut course of tiles
Also I think the splash lap size is working against you. certainly it should be raked back on the sides rather than a straight cut across the gutter

Thanks for that. It's certainly a very plausible theory, and the one I am working on at the moment and I have taken temporary measures against.

It would explain why the problem only appears after heavy snow, when it is sat on the flat bit, or water is running onto the flat bit before hitting snow/ice and then travelling backwards through the two layers of lead. Torrential rain just moves quickly along the bottom bit of the gulley.

Anyway, there's a nice amount of snow sat in the gulley as I type, so hopefully my bodge will prove us right when it thaws.

I don't quite understand your last sentence though, the raking back bit at least.

 

[quisquose]

All the snow's gone ... and no water ingress this time.

My guess is that datarebal was correct with his theory, and just putting a bit of flashing tape on the join stopped the water from tracking back.

Thinking about a permanent solution now, if I ever get around to it.

 

[quisquose]

"Ha, ha ... so you thought you'd fixed it did you ... you thought last weekend's sprinkle was enough to test your bodge did you? Mehawahhh!"

So there I was with my buckets in the middle of last night, collecting the water dripping through the ceiling, when I realised that my optimism of a few days ago was very premature.

I've not actually had to collect the water before, about a bucket full, and don't think it's a result of anything I've done, it was just the conditions that defeated our gulley.

Here's a picture taken at about 8:00pm. No damp patch at this point.

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• quisquose
• 14 Feb 2013
• 1

Here's two more taken just 3 hours later. It's thawing quickly, and raining hard, and a damp patch has appeared on the ceiling. The top of the ceiling is damp from the attic, but there's no visible source of water ingress from above.

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• quisquose
• 14 Feb 2013
• 1

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• quisquose
• 14 Feb 2013
• 1

Poking the ice sat in the gulley and it's pretty solid. Two hours after these photos are taken the damp patch has spread to the largest size I've ever seen, and I'm collecting water in buckets.

It has to be tracking back in the bottom of the gulley. Is this even solvable? The design of the roof is such that I could imagine a devastating snow fall overcoming the gulley no matter how well it has been constructed.

Time for trace heating perhaps?

 

[Nige F]

"Ha, ha Time for trace heating perhaps?

 

[quisquose]

Nige F 1 quisquose 0



I'm thinking something in the lower third of the gulley, down the slope into the gutters, to move the snow ice from there so the thawed water can shift in the right direction.

But what, and where from?

 

[catlad]

You could get one of them electric tube heaters that people put in outhouses to keep the chill off, they are cheap to run, if you could fit it under the valley board that should melt the snow.