New Lead Valley leakage!

[Mickey]

Hi All,

We have recently spent a not too small amount of money on our roof to try to get it watertight including replacement 2 x lead stepped lead gutters (the ones that are flat but with stepped joints and sit in between two roof pitches (yes you can tell I'm not a roofer!). During last night's latest biblical proportions of rain one of these valleys leaked which culminated in it dripping down the main beam which runs from front to back inside our property depositing water onto our newly fitted oak worktop in the kitchen. I've got someone working there at the moment who has been up on the roof and said can't see any reason for it to leak but "there are alot of leaves in the valley". Now before the roofer arrives to take a look later this afternoon I'd just like some advice as to how on earth leaves laying in the lead gutter could possibly make it leak like that, surely they might run off and go down and block the downpipe but surely not make lead leak or am I going mad which after all the many issues we've had with this house could be a distinct possibility!

many thanks
Mickey

 

[LadyArowana]

Not sure I totally understand what is happening, but the combination of biblical rain and leaves sounds like the recipe for a leak. Perhaps the gutter just wasn't big enough to cope and isn't correctly lapped into the roof? Hope the roofer can fix it easily and thrworktop recovers too.

 

[Mickey]

Many thanks for reply Lady A, gutter might be the wrong word, it's about a foot wide by 10 feet long water should run off the surrouding roof valleys onto it, it's stepped (due to the length of the lead) and water should flow into downpipe. It's only been done about a month ago, worktop was fitted the day before but not yet oiled but thankfully not damaged a light sand and no marks but not really what a wanted to have to deal with at 11pm last night, we are in Cornwall so more rain to come

 

[Flyfisher]

Leaves won't magically make lead leak, but they can block the water flow such that it backs up and finds another route to escape. Simplistically, imagine a gutter blocked by leaves - the blockage will act as a dam, the water in the gutter will rise and eventually overflow the gutter.

If I've understood this particular problem correctly, there is a lead 'gulley' between two roofs. If water cannot flow out of the gulley fast enough (could be various reasons, including a blockage or just being too small to cope with the roof run-off during very heavy rain) then the water in the gulley will rise and perhaps 'overflow' the gulley. What will happen then will depend on the roofing membrane arrangement, but at some point rising water will be able to find its way up and under the membrane and then flow back down the outside of the lead gulley and thence into the house.

 

[88v8]

Perhaps the lead hasn't been taken high enough under the tiles.

Another potential problem with box valleys is snow. When it thaws, the top melts, but because it's sitting on the frozen snow beneath, the melt water flows under the tiles and over the top of the lead, and into the house. To prevent that, you should have some of this in the gutter
http://www.traceheatinguk.co.uk/product?pid=456&nm=Raychem+WGRDFS-A-2X+Heat+Trace+Cable+(10+w%2Fm+at+5%C2%B0C+)&gclid=CKWv1pvCm8ECFc7HtAodVn4AXg
and when snow is threatened you switch it on, so the snow can't settle.

As to the valley, guess you need to climb up there a couple of times in the autumn to clear the leaves.
And the lead should be taken higher up the slopes, and where it overlaps, the laps need to be welded.

It's not enough for a valley to deal with water coming down the roof, it also has to deal with build-ups when the outlet is blocked.

Valleys... always a potential pain.

Ivor

 

[Lime]

The laps need to be properly constructed not welded.
Welding will eventually split the lead due to its almost constant expansion and contraction.
There is no other reason for the valley to leak except that it has not been correctly constructed.
The embedded problem is usually out of sight and exists because the lead is cut short in places and/or the joints are not correctly made.
It never ceases to amaze me how roofers who do lead compromise their work for a few pounds of lead.
They work on the principle it looks good so who is to know, then go off hoping it doesn't rain hard for a while.
Often the only solution is a complete rework of the leadwork.

The guide to good leadwork tells you all you need to know.
Find the guide and other information listed in the "construction" tab in this link:

http://www.calderlead.co.uk/downloads/

What a pity more roofers don't read it.

 

[MatthewC]

My excellent lead worker moved to Cornwall (eastern end). Would you like his details?

 

[Mickey]

Thanks everyone for replies, according to the roofers it was leaves, we had very strong winds here on Monday night and then torrential rain on Tue night and the combination formed a plug of leaves which allowed water to back up over the step and somehow leak. I agree with Lime that it's probably lack of care and improper installation because on the other lead gulley which has just been done we have 'ponding' where they have installed it with insufficient fall (I've just read Lime's leadwork attachment so now know the lingo) when we pointed this out the roofer suggested to alter this would incur us more costs!!! We await the next torrential downpour to see what happens. Yes please MatthewC if you could pass me the details of your lead specialist because we still have another small roof to do which will require leadwork I won't be using the same roofer either of all the trades we have used here they have been a nightmare!

Thanks again everyone.
Mickey

 

[Flyfisher]

I've often wondered about the suitability of lead for things like lined gutters and long gullys, where the lead had to be welded to form waterproof joints, when all the guidelines for things like valleys etc emphasis the maximum lengths of lead to allow for the inevitable expansion /contraction that will otherwise cause inevitable failure.

Is this an example where modern materials - fibreglass perhaps? - would actually be far superior to lead work? Especially as the lead lining of gutters and gullys is usually completely invisible anyway.

Where is our resident lead expert when we need him? I'm sure Doug could explain how such things should be done.

 

[Lime]

I've often wondered about the suitability of lead for things like lined gutters and long gullys, where the lead had to be welded to form waterproof joints, when all the guidelines for things like valleys etc emphasis the maximum lengths of lead to allow for the inevitable expansion /contraction that will otherwise cause inevitable failure.

Is this an example where modern materials - fibreglass perhaps? - would actually be far superior to lead work? Especially as the lead lining of gutters and gullys is usually completely invisible anyway.

............................................

No I don't think so.
All the problems with leaking lead roofing can be directly associated with incorrect installation practices.
That of course can be a number of things, including the lead thickness being too thin and/or dimensions being too large, but in general I think it fair to say that the majority of problems arise because the lead is not physically installed correctly in the first place.

As for your comment about fibreglass, have a look at the "Truth About Lead" video in my link in my previous post.
Some of the facts in it may surprise you.

 

[Flyfisher]

Fair points, especially about lead longevity compared to some modern materials, though even the Lead Sheet Association endorses modern sealants to secure flashing rather than using mortar fillets.

I take the point about incorrect installation, and the recommendations for gutters and horizontal gulleys being stepped rather than welded are fine and understandable, but they can clearly lead to leaks if 'ponding' does occur. Perhaps this is what has happened in Mickey's case?

So, yes, lead might last longer than (say) a continuous fibreglass structure, but it is also going to be more susceptible to leaks if ponding occurs - and let's face it, gutter maintenance is frequently overlooked!

Not that I would advocate using anything other than lead for flashings and the like, or anywhere else where pooling is not a potential problem, because well-dressed leadwork is certainly a lovely thing to see.

 

[88v8]

In our previous house we had a lead valley between the two slopes of the original roof and the 1990 extension. About 15ft x 1ft.
All joints were welded. It never leaked, nor cracked, and I checked it every year when I went up there to clear leaves. Mind you, it didn't get the sun on it, I think that makes a big difference.

Ivor

 

[JoceAndChris]

Sympathies. We have the same problem around our porch, and I don't know how to fix it either except by a quarterly gutter clean.

 

[a twig]

Our rather large centre valley was re-done in lead. Maybe 20m long, 2m wide at one end, narrowing to about 0.5m at other.

Lead went best part of a foot up under the tiles, and rubber type expansion joints were fitted every metre (ish) as it gets a lot of sun.

They also put in more steps as previous lead work was causing water to flow the "wrong way".

It's been spot on, I have a peer up there every few months to see if it needs clearing out, but the volume of water that comes through during a rain storm seems to keep it pretty clear.