Leak at gable end of roof/skews

[Kaymo]

Hi,
Got a bit of a leak coming in at the gable end wall upstairs. There was dampness in an old Edinburgh Press (shallow cupboard set into stone wall) which I thought was condensation and I ripped the wooden lining out to find a leak coming in from above. No dampness or water ingress at all in the attic space above, and as the cupboard recessed into the wall, I presumed it was probably coming in at the skew stones and seeping down the inside of the wall until it hits the open space at that cupboard.

House is at least 150 years old with slate roof,

Got one roofer out and he seems to have come to a similar conclusion. He said that he couldn't see any issue with the cement skews/fillet, but that the stones become porous with age. His suggestion is to cover the stones completely with lead, running under slate, and I am now awaiting quote.

Just wondering if there are any thoughts/alternatives or things that I should consider.

Thanks.

 

[Sonic70]

Photos inside and out always helpful.

 

[Kaymo]

Photos inside and out always helpful.

Of course.

The pic is the cupboard which is in the corner of the room (the corner where the drainpipe is in the outside photo). Water seeping in through the stone above the wooden lintel for the recessed cupboard.

No pic of attic as its a nightmare to get into that point again, but it was dry as a bone above, which makes me think the water tricking down through the centre of the wall.

Outside pic of gable end of roof where I think it is entering.

 

[Nige F]

I've had a Google and found " Compass Roofing " Edinburgh - Just an idea as they do leadwwork - I'm as far from there as possible - on the S.E Coast Hope this helps though.

 

[Notch7]

Of course.

The pic is the cupboard which is in the corner of the room (the corner where the drainpipe is in the outside photo). Water seeping in through the stone above the wooden lintel for the recessed cupboard.

No pic of attic as its a nightmare to get into that point again, but it was dry as a bone above, which makes me think the water tricking down through the centre of the wall.

Outside pic of gable end of roof where I think it is entering.

it looks like the parapet gable needs re leading.

Id guess that needs a scaffold to be done

 

[Kaymo]

it looks like the parapet gable needs re leading.

Thanks. I had to look up parapet gable, I think the roofers around here call them skews.

There is no lead on them at the moment, its cement between the slate and the stone. If I understood correctly I think the roofers that were out were proposing covering the entire skew/parapet with lead, and running it under the slate with a kink in the lead (under the slate) to prevent run back.

I am a little sceptical that the sandstone is porous enough for water to enter so quickly after rain, but maybe if they are already saturated, I don't know. I suppose the idea of running lead over everything means that it takes everything out of the equation from the stone to the seal between the stone and the slate.

 

[Kaymo]

I'm still waiting on a quote for covering the copes/parapet with lead. I have been told it will need scaffolding, which means it will be expensive. I'd also have to do at least the other side at the front or it will look odd, which means double the cost.

However, I am still trying to get my head around the idea that the coping stones would become porous and water coming directly through the stone. I could see this more on flat parapet walls, but with the slope the water isn't going to sit on the surface. Does anyone have any direct experience of water coming through the coping stones like this?

I know that the joint between the coping stones and the slate is a weak point for leaks, its currently cement, but a lot of houses around here have this done in lead, and the joints between stones could also be an entry point for water, so usually what I have seen done around here is the joints repointed, and the skews/fillet redone in cement, or lead. Recently I saw this done on a house across the way with something that looked orange to begin with and faded to grey over time, so I presumed was some kind of new, flexible alternative to cementing the skews.

There are loads of houses around here with the same design, and I see some of them having the skew redone, but have never seen any in this town that are completely covered in lead. I get the fact that covering them in lead leaves nothing to chance, and its not so much the cost that I am concerned about, rather how it will look. The house is in a conservation area, so I would probably need planning permission to cover the cope in lead.

Really just wondering if any of the roofers typically cover the whole parapet with lead, or if you have sealed the skew and pointed the joints and still found water coming in, pointing to porous coping stones?

Thanks again.

 

[Alastairreid]

Get the skew and joints between the stones re-done first, that can be done from a roof ladder unless it's a 3 storey.

 

[Kaymo]

Get the skew and joints between the stones re-done first, that can be done from a roof ladder unless it's a 3 storey.

Thanks Alastair. That's a good plan, provided I can find a roofer willing to do that. I've had two out so far and both are talking scaffold and fully covering the skews with lead. The one that came yesterday said he would be including replacement of the sarking at the skew in the quote because he expects it to be rotten.

I'll see if the final roofing company coming today says the same, and can broach the idea of doing the skews and joints only first.

 

[Alastairreid]

He only needs to look in the attic to see if the sarkings rotten.
Of course they will want to do the more expensive alternative.

 

[Kaymo]

He only needs to look in the attic to see if the sarkings rotten.
Of course they will want to do the more expensive alternative.

Good point, but its not that easy to see because there is an attic room, although the part I can access there was no water ingress or signs of rot when I checked last week.

However, does the sarking run all the way up to the edge of the cope or only to the edge of the gable wall?

I'd imagine if the sark runs up to the edge of the cope you wouldn't be able to see if they were rotten at the edges, but I don't know how its normally constructed.

 

[Alastairreid]

The sarking runs up to the edge of the last rafter which runs up the side of the gable wall, the cope oversails the sarking and slates which is where the cement fillet/skew is formed.

 

[Kaymo]

The sarking runs up to the edge of the last rafter which runs up the side of the gable wall, the cope oversails the sarking and slates which is where the cement fillet/skew is formed.

Ok thanks, given that the wall is much wider than the cope, if the cope oversails the sarking even slightly, a section of the sarking will be sandwiched between the top of the wall and the slate and will not be visible from the attic. Although that may only be about 150-200mm, which is a good bit less than the roofer was quoting to replace.

My gut tells me that the water is coming through or under the cement skew, as the rain usually drives towards this junction from the south west. Water coming in at this point would enter the inner skin and run down the small rubble fill cavity, which seems to be roughly where it is entering the cupboard inside.

Water coming through a saturated cope would mostly come in to the outer skin of the wall, which you might think would be less likely to appear so high up on the inside skin of the wall, but its obviously hard to predict the course that water will take through a wall.

Its difficult though, if a tradesperson tells you what needs to be done and you suggest otherwise, it usually doesn't go down well and both so far have been quite insistent that most of the water will be coming through the sandstone cope.

 

[Alastairreid]

I coated a sandstone cope with a couple of coats of thomsons Water seal a few years ago, the customer had the same problem as you, no problems since. That was after renewing the skew and re-pointing the joints.

 

[Kaymo]

I coated a sandstone cope with a couple of coats of thomsons Water seal a few years ago, the customer had the same problem as you, no problems since. That was after renewing the skew and re-pointing the joints.

Interesting, I was thinking about a paint on sealer, so good to hear this has been done before with success.

Sorry to keep asking more questions, but did you do the water seal at the same time as renewing the skew/pointing, or was it still leaking after this and you came back and painted on the water seal? (Just curious if you know which of the two was the main culprit)