Lead gulley leaks when heavy snow thaws

[quisquose]

We have a large gulley which had always had problems with leaks. A few years ago, and at great expense we had it totally overhauled with new lead, an increase in the fall and an expansion point added.

The plumber that did the work came well recommended, and clearly knew what he was doing.

Since then the gulley has coped admirably with torrential rain, but on the 3/4 times when we have had thick snow it has leaked when it has thawed. I had assumed that it was down to ice dams, and was determined to witness where it was coming in with the next thaw. This was last Saturday.

As the damp began to appear in the spare room I began to watch in the attic space, expecting to see water dripping back through the Rosemary tiles (there is no felt). But nothing ...

The only conclusion I could make is that the water was finding it's way through the lead itself, and the fear was that the lead had failed. After a while a damp patch appeared on one of the purlins that the lead is wrapped around. When I pushed a plastic marker through the tiles at this point it coincided precisely with the point in the lead where it overlaps.

I can only imagine that after heavy snow, thawing snow is icing up and squeezing itself back through the two layers of lead. It overlaps for about 12 inches.

Does this sound a sensible reason? If so, I could imagine that some flashing tape on the join might just stop ice and thawing water from travelling upwards at this point. I hate the idea of using flashing tape since this is how the previous house owners bodged it, but since it's not really making a temporary repair but just adding a defence against occasional travelling ice I would be willing to use it.

Any suggestions?



From left to right just after new lead was installed in 2008, and just before tiles were replaced:

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...

The picture above is where the problem is. Where the lead overlap, about a metre from the end is where the water is getting in after heavy snow. I suspect that ice sits in the bottom metre and forms a dam in the gulley and when it starts to melt the water is unable to fall off the end and squeezes back through the two layers of lead.

There are no problems with the centre and right of the gulley, or the valleys.

The centre of the gulley.

• quisquose
• 4 Feb 2013
• 1

No problems here.

The right side of the gulley and valleys.

• quisquose
• 4 Feb 2013
• 1

No problems here.

The gulley is accessible through a Velux window from the attic.

 

[datarebal]

Pretty basic stuff .. I cant see any expansion joint, Looks like there maybe a step in the lead as there should be. A 12 inch splash lap is excessive!! probably doesnt

 

[palaceray]

I think you should check that the step in the box gutter is a minimum of 50mm and that the lomer gutter section is properly dressed up the step to prevent water creeping back.

 

[cotswoldbuilders]

I agree with the above, you should have had some steps in the valley.
Plus a lot neater job if he had used chase wedges to dress the lead in tighter to the edges.

 

[quisquose]

Pretty basic stuff .. I cant see any expansion joint, Looks like there maybe a step in the lead as there should be. A 12 inch splash lap is excessive!! probably doesnt

There's a neoprene expansion joint welded into the lead in the third photo.

At each overap in photos 1 and 2 there's a drop of about 2 inches, but this is not too clear in the pictures.

Your 1st unedited post was somewhat dismissive of the guy who did the work. but he came highly recommended and it was certainly an improvement on the original 1933 lead.

It cost us a few bob too! I'd rather not go through all this again.

 

[quisquose]

I think you should check that the step in the box gutter is a minimum of 50mm and that the lomer gutter section is properly dressed up the step to prevent water creeping back.

Not quite sure of the terminology here, but there is a drop of about 50mm between the left piece of lead and the centre piece. This is the only area where we get slight water ingress, and only after heavy snow.

 

[quisquose]

Just found another photo taken last year whilst we were having our ridge tiles re-bedded:

From the end of the gulley

• quisquose
• 4 Feb 2013
• 1

Image from 2012 whilst we were having the ridge tiles rebedded

I know the step in the background is 2 ins, so I think the step in the foreground is about 3 ins. It's the latter where we get a small amount of water ingress, but only after very heavy snow (which could quite easily cover the lower ridge tile) begins to thaw.

I suspect the lowest point of the gulley could be solid ice at this point.

I should also add that the slope to the left faces SE, and can thaw quite quickly. It's the room under this side where the damp patch appears.

 

[yorkie1969]

I understand and respect that your plumber came highly recommended. However, it does not mean he has necessarily done the job correctly, and, in fairness, whilst it looks neat and tidy to you, to people in the trade it does not.
It has not been dressed in correctly. The steps should be at a sharp 90 degree angle, not the slope that we see. This is aiding capillary action which I believe to be the problem here. Added to that, he has nailed it all the way down the sides and has even nailed 2 bays together, effectively making it one oversized bay causing a problem with the thermal movement. Furthermore, he has nailed the bay where the expansion joint is which just makes the expansion joint a waste of his time and your money as it cannot move properly.
You need a local leadwork firm to come and peel back the drips and sort them out, possibly making an anti capillary splash lap whilst they are there.
They need to take the nails out of the sides of the bays to so only the top third is nailed, except the bay with the expansion joint, no nails in that whatsoever.

Kind Regards,

Mark.

 

[noseall]

Why don't you replace that broken tile directly above the problem area first?

 

[quisquose]

Why don't you replace that broken tile directly above the problem area first?

The photos were taken in 2008, and the broken and shot tiles were replaced when the rest were relaid.

 

[joe-90]

Look at those hip irons.

 

[quisquose]

I understand and respect that your plumber came highly recommended. However, it does not mean he has necessarily done the job correctly, and, in fairness, whilst it looks neat and tidy to you, to people in the trade it does not.
It has not been dressed in correctly. The steps should be at a sharp 90 degree angle, not the slope that we see. This is aiding capillary action which I believe to be the problem here. Added to that, he has nailed it all the way down the sides and has even nailed 2 bays together, effectively making it one oversized bay causing a problem with the thermal movement. Furthermore, he has nailed the bay where the expansion joint is which just makes the expansion joint a waste of his time and your money as it cannot move properly.
You need a local leadwork firm to come and peel back the drips and sort them out, possibly making an anti capillary splash lap whilst they are there.
They need to take the nails out of the sides of the bays to so only the top third is nailed, except the bay with the expansion joint, no nails in that whatsoever.

Kind Regards,

Mark.

Thanks for that, you've certainly given me something to think about.

The photos don't make it very clear, but the steps are a sharp 90 degrees steep.

I take on board what you say about the nails, and may get out there and do what you recommend in the summer. However, whilst the current fixing might put some stress on lead and reduce it's life expectancy it is still relatively new and seems to be in okay condition at the moment.

My immediate concern is the small but predictable amounts of water ingress with each thawing of heavy snow. So I am interested in the suggestion of an anti capillary splash lap. If the lead at the problematic drip is peeled back, how is one fashioned?

Ta.

 

[quisquose]

Look at those hip irons.

Wickes £5.69 each.



Unfortunately, the builders who did our extension did turn out to be cowboys and it was they who replaced the tiles, not the plumber, so wasn't suprised to see these and the reason I took the photo. Classic.

I've no idea what was there before though, maybe nothing.

 

[Nige F]

Consider trace heating for the outlet area - have a google

 

[noseall]

Look at those hip irons.

In all fairness, the lead may go up higher than a standard hip iron fixing would allow, without puncturing the lead.

Probably.