refurbing old slate roof

Hi,
Looking for help with my roof. Intending to refurb my old slate roof due to regular leakage problems. So far leaks mainly due to cracks in the chimney plastering and in the lead gulleys (lead sheeting far to long to take up expansion without cracking. Couple of questions at this point - should I replace lead with new properly laid lead sheeting or go for a felt (?) material as my neighbours seem to have done. Would like to get a hold on the price differential and the lifetime diiferential of both materials. - is it advisable to re-use slating which is the old fashioned, large hand cut slates or replace with the modern, smaller standard slates - what needs further paying attention to in a job like this.
thanks for your help, John
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On Fri, 10 May 2013 04:01:16 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

Not quite sure what you actually mean by "lead sheeting" and where this is. If you mean the lead flashing that joins the chimney stack to under the slates then use lead. Properly done it will outlast you and the roof. Think 40+ years... Lead isn't that cheap but it will last far far longer than anything else, when properly done.

hand cut slates or replace with the modern, smaller standard slates
If they are still sound re use. Again a good slate roof has very long life. You'll inevitably break some (or they'll fall apart) when you strip the roof. You'll get an idea then how sound most are, if they still "ring" when gently tapped they are "sound".

The timber underneath (rafters and purlins) and the sarking. If you are stripping off replace any iffy looking rafters/purlins and the sarking with a modern breathable membrane rather than traditional sarking felt and use new treated laths.
At the eaves use something that can take the weather and light exposure, even though it's under the slates the very edge is exposed over the gutter. One roof here has 2' wide DPM along the bottom edge, the section that was adjacent to the flat roof replaced last year has some sort of thick semi-rigid coated metal stuff that is about 1/8" thick.
Copper nails are supposed to be used but TBH hot dipped galvanised clouts last a very long time. In theory slight slate movement is suppossed to wear away the zinc and allow the head to be rusted off. In practice I don't think this happens, at least not in a time scale significantly less than the life of the roof anyway.
--
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Dave.
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Lead should last more or less for ever, if properly done. Felt depends on lots of things - but say about 20 years.
If the lead has split due to expansion and not having expansions joints. it may be possible to cut in a section with those, rather than total replacement.
--
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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On 10/05/2013 12:51, Dave Plowman (News) wrote:

When ours was done approx 20% of the slates were naff and needed replacing. The roofer hits them with a screwdriver handle, and if they "ring" they get used, otherwise they go in the skip. Fortunately they're available secondhand for a quid apiece. The varying thicknesses also have to be taken into account and not all roofers can handle that. I much prefer the Welsh slate to the Chinese or Spanish stuff, and I don't like the look of Eternit, especially when the sun's on it
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On 10/05/2013 13:24, stuart noble wrote: ...

I had a slate roof in Sussex replaced, probably about 25 years ago now. It was an extension that had been done in rather nasty mock slates that did not match the Victorian slates on the main roof. It worked out a lot cheaper to drive the Wales, stay overnight, and bring back a ton of slates, made to order at the mine (including 1.5 width slates for the ends), than to buy them second hand locally.
Colin Bignell
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Well worth it to replace the lot and the roofing felt all at the same time.
--
Tim

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To hijack the thread just a little: A top floor flat in a Scottish tenement building where the roof was completely and expensively renovated 10 or 20 years ago is perfectly dry in wind and rain, but occasionally gets a minor flood from above the sash windows when there is a very extreme downpour (happens maybe 2 or 3 times a year).
I assume that this is because the rhone, the roof gutter, can't cope with tropical-style rainfall.
At the moment the rhone needs to be cleaned again to remove vegetation, but the problem happened even when it had been recently cleaned.
There's no legal mechanism for doing necessary repairs and splitting the cost among the dozens of owners, except that the Council has the power to do the work and charge us all.
When I asked the Council to do something about the rhone problem, they somehow came up with a proposal to completely replace the whole roof - again - at a cost of around 45,000. That (and several similar cases elsewhere) resulted in a police investigation over accusations of fraud, with the result that the City will now do no repairs other than emergency work.
Which leaves me with the question of what might cause the leakage problem. I asked a couple of roofers, but they didn't seem to want to deal with anything except a couple of loose slates. That should be done, but there's no actual leak at present.
Anyone know what if anything could be done? If I have some reasonable proposal in mind, it could be presented to the other owners with some slight chance that they might agree to the work. (Though in their eyes I'm the bad guy for involving the Council in the first instance.)
I can climb onto the flat part of the roof, but have no way of getting down the sloping part to the rhone to examine it. (And at my age, probably shouldn't even think of trying).
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On 13/05/2013 04:34, Windmill wrote:

Are the windows on the inside or outside? In other words, where is the sill? If the wall gets really soaked due to driving rain, water will travel downwards inside the masonry till it hits the window opening. I imagine there should be some kind of waterproof membrane above it?
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The sash windows (replaced when the roof was last repaired) seem to be set into the stonework above - that would I suppose be called the stone lintel or maybe sill. So they're neither on the inside nor outside; they're in the middle.

Driving rain isn't a problem. The only time there's a leak is when the rain is coming down like a wall of water (which seems to happen more often nowadays). A vertical downburst of rain.

Maybe there should be something of the sort at the edge of the roof just under the level of the rhone? If it had been accidentally omitted, that might explain why water comes from *above* the wooden window frame.
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On Tuesday, May 14, 2013 2:08:24 AM UTC+1, Windmill wrote:

I dont think Ive ever seen a building with sliding sash windows AND a waterproof membrane above them.
Deeper gutters? Greater gutter slope?
NT
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On Mon, 13 May 2013 19:22:02 -0700 (PDT), snipped-for-privacy@care2.com wrote:

<snip>

Scottish tenement... I don't think it will have a "gutter" as in trough hanging below the edge of the roofing material. I think a "rhone" is more like a gully behind a parapet wall. Google isn't very helpful.
More description of what is actually there from the OP required.
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I think we had an earlier thread on this. My vague recollection is that the Scottish gully has no fall.
On safely accessing a sloping roof (perhaps not for the OP) A rope secured at a higher point can hugely reduce the risk of tumbling over the edge.

--
Tim Lamb

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About 60 feet up. Not at my age, unless something was life-or-death.
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I'll take some pictures, if I can.
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On 14/05/2013 02:08, Windmill wrote:

Might be to do with the window replacement, which often leaves a hollow cavity above the frame. This really needs to be packed tight with mortar rather than a squirt of foam, but installers don't have time for that.
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I think that might be the case, but am not sure how the stonework is arranged.
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Lead life, if well laid, is up to 70 years.
For a sloping valley gutter between adjoining roof faces, you can get preformed GRP lengths, which is a less skilled fitting job. I had that fitted 25 years ago. 8 years ago, I stripped and replaced the roof around it (for other reasons), and it was still fine, so I left the GRP unchanged (except for adding replacement mortar bonding strips down the sides, for repointing the valley).
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Andrew Gabriel
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