Another soaker/flashing thred - slate with cob abutment

[Zalas]

Hi guys,

I've spent a fair few hours searching many good threads and posts on here and various other DIY sites but I'm still not entirely clear in my mind...

Our roof is a slate roof that on one side has an abutment to a flying cob freehold (owned by neighbour). The bit that abuts is the original house (1836) but the rest of the roof below is from an extension in the 90's (original roof redone from the looks of it as poor attempt at felting exists in the loft).

The problem is that in Feb (moved in during October) the "duct tape" attached bit of gutter fell off the downpipe from next door so water was cascading along the edge of the slates and next door





We assumed it would be OK as there'd be soakers etc. and it could be a "get round to fix with proper routing of drainpipe" later, along with removing the cement fillet and doing it properly.

The (not quite as old as we thought) water mark had been getting bigger but now we actually got drips requiring the placing of various pans underneath.

We recently had the other aspect re-slated and I got the roofer to have a good look while he was up there as we were keen to try and fix it. It turns out that seemingly all that is protecting the slates / abutment is a bit of roofing felt over the slates (can just see it in the following pic)

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• Zalas
• 23 Aug 2011
• 1

Looking from inside the (very cramped) loft space I found the following - you can see drip marks on the cob wall and the timbers look decidedly dark and wet.

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• Zalas
• 23 Aug 2011
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• Zalas
• 23 Aug 2011
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You can see where the felt has ripped and is sagging

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• Zalas
• 23 Aug 2011
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(please ignore the mouse poo )

Looking back towards that perlin the underside is quite interesting:

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• Zalas
• 23 Aug 2011
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Wet!

SO that's the background complete.

The question is:

I want to install some leadwork to make everything kosher and dry. Next door has what I assume is soakers with a cover flashing over the top - but it also looks like they've just dressed and bossed the lead over the slates - do they even have soakers I wonder now as I can't see any kick/tell tale lump in the cover flashing where it is dressed over the upstand.....

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• Zalas
• 23 Aug 2011
• 1

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• Zalas
• 23 Aug 2011
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I don't know if we have soakers present or not, it's certainly not clear from inside the roof (I know they're interleaved in the courses but thought I might be able to see).

So - if we haven't, and I want to fit them, I think it's going to be a case of getting a slate ripper and every other lap - correct? Then running cover flashing over once the slates are replaced.

*Or* and this is the big *or* - would simply having 6" upstand and then a cover flashing coming out 10mm over the middle of the half-slate be sufficient?

Cheers,

Zal.

PS Edited to say that bigger pictures can be provided if required!

 

[Blagard]

Hi guys,
So - if we haven't, and I want to fit them, I think it's going to be a case of getting a slate ripper and every other lap - correct? Then running cover flashing over once the slates are replaced.

The every other method means you have a soaker a full slate length fitted below the slate. That means the lead is not supported until it reaches the next slate below. - Not the right way to do it.

Your soakers should be on top of the slate (and so fully supported) but only one gauge and lap long (plus a bit turned over the top of the slate/batten). Fitted every course.

The lead on the abutment in your photo almost certainly has no soakers in it. There is no point to dressing lead over the slates like that if you have them. You only do lead like that if you are going over a profiled roof tile.

 

[Zalas]

The every other method means you have a soaker a full slate length fitted below the slate. That means the lead is not supported until it reaches the next slate below. - Not the right way to do it.

Your soakers should be on top of the slate (and so fully supported) but only one gauge and lap long (plus a bit turned over the top of the slate/batten). Fitted every course.

Ahhh interesting - the roofer said to remove every other slate... your justification makes a lot of sense though! Suspect I misunderstood the roofer - confused between laps and slates. With a maximum length of one gague I'll have to remove all slates up that side of the abutment, yes?

The lead on the abutment in your photo almost certainly has no soakers in it. There is no point to dressing lead over the slates like that if you have them. You only do lead like that if you are going over a profiled roof tile.

Forgive my ignorance but why? If you have the overlap long and dress the lead tightly enough wouldn't it still provide a good waterproof covering? I'd imagine it would take an awful lot of water and wind for the capillary action to traverse the entire led sheet?

 

[Blagard]

Forgive my ignorance but why? If you have the overlap long and dress the lead tightly enough wouldn't it still provide a good waterproof covering? I'd imagine it would take an awful lot of water and wind for the capillary action to traverse the entire led sheet?

The water running down your slates generally runs straight down with a little spread sideways with both wind and volume action. Your lead is not actually fixed where it is dressed over the slate and will to a degree lift.

As the water that does get under the lead goes down the roof slope, it will work towards the edge of the slate which has no "stop edge" like a soaker.
Think of the water coming down a slope several metres long with no edge to prevent it going off the side.

You may be fortunate enough not to have a problem, but the design does not provide the assurance it will not leak that a proper soaker arrangement will. If I can find a publication that illustrates the problem I will update

 

[Zalas]

No need, it makes perfect sense!

I've just been out with my stumpy ladder and camera and have an interesting update:

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• Zalas
• 23 Aug 2011
• 1

I see lead! This makes me think there may be lead present under the laps ... They do appear to be mightily ineffectual but could that be because there's no cover flashing over the top? I've taken a close up as best I can going up the rest of the aspect but I can get little better than a "reach the arm and click"

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• Zalas
• 23 Aug 2011
• 1

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• Zalas
• 23 Aug 2011
• 1

If it is as I hope then maybe just maybe it'll be a smaller job..?

 

[Blagard]

Your photo makes perfect sense.

Even my own home (1930's era) has similar details. Soakers fitted, turned up the wall and render brought all the way down over the soaker. Covering the soaker with a cement fillet is similar. Both are effective at stopping water running off the roof slope.

Trying to find information on how not to do flashings is tough! - I can only refer you to the lead association and a consultancy. You will not find the detail of the lead in your earlier photo in either!

http://www.leadsheetassociation.org.uk/autocad-online-flashings

http://www.thetiledroofingconsultancy.com/articles/STT_set_1.html

 

[Zalas]

I've become intimately familiar with the LSA website, but that other one I've not come across before! Interesting reading.

So, if this is the case and the soakers are merely rendered over, it begs the question where on earth is the water coming from?!

I think a lot will be resolved by fixing the guttering properly - maybe the soakers aren't very high and the water is permeating through the lime render and down behind them?

 

[Blagard]

With a maximum length of one gague I'll have to remove all slates up that side of the abutment, yes?

Oops! missed that one - With every other slate removed you may be able to "fiddle" the soakers in on the remaining fixed slates. I have never actually fitted a slate roof myself so I don't know the tricks of the trade. I snagged a considerable number (hundreds and the worse one they had to take it all off and do it again!).

Truth be told I don't know how you can get the soakers in without removing the inverted triangle area. It's all a question of how you fix the slates. It is dead easy with tiles

 

[Zalas]

Truth be told I don't know how you can get the soakers in without removing the inverted triangle area. It's all a question of how you fix the slates. It is dead easy with tiles

That triangle is hopefully going to come off! I was planning on removing those slates and re-doing it properly...

With regard to the soakers and where the slates / verge / abutment meet going up the rest of the house it'll be a case of "watch this space" and see what I find once I'm up there.

Many thanks Blagard.

Cheers,

Zal.

 

[Zalas]

So, if this is the case and the soakers are merely rendered over, it begs the question where on earth is the water coming from?!

I think a lot will be resolved by fixing the guttering properly - maybe the soakers aren't very high and the water is permeating through the lime render and down behind them?

Blaggard - Just before I disappear until further inspection is completed could I trouble you for one last snippet of wisdom? Have you any ideas (assuming the lead does carry on up) where/how the water could come in? I suppose cracked/damaged soakers is also a possibility...

 

[Blagard]

If, there are soakers there I really would not expect there to be problem. However, your leak very clearly identifies there is a cause and it needs to be investigated.

I would be inclined to remove the cement fillet above where the leak has occurred and work upwards. I would put money on the fact that whoever re-roofed the property has bodged something or the shear volume of water coming down from that downpipe is spashing up over the fillet (which may have split away from the wall) and is going down the back of any soaker (which I am not convinced have been fitted!).

That bit of lead you see is not turned up the wall as a soaker should be, and is probably just at the bottom to allow the cable in. A slate would really kickup if laid over that cable.

I'm sure all will become clear once you start to uncover things!

 

[Zalas]

Right an illuminating update. After walking 3 miles to and from Brandons to collect the roof ladder (2m + 2m extension) I've decided there's no comfy way to carry a ladder.

Second update: Got the ladder up on the roof and had a good look (no pics yet). Nothing but knackered roofing felt is present and it's just a single thin layer, most of which has holed and fallen apart. I can look through the hole into the corner of the wall and down into the roof ... that's why it leaks!

So, tomorrow brings soakers and 300mm overflashing.

Yay!

Oh, and also found that the aerial we have on our side of the house isn't actually used!! We're fed from the neighbours aerial bizzarely.

Also found a patch of leadwork on the other side of the house which is really poor lead flashing strip which hasn't actually been sealed down.

COWBOYS!