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    what's the best thing I can do to fix this flashing? A small leak is evident below when there is heavy rain. All the neighbouring chimneys have been similarly rendered and have mortar flashing. Could a sealant be used to seal the gap between the slates and the mortar? How would this gap be sealed if traditional lead sheet were used?
    Can't open the pic
    here's another
    Oh, how weird! Now I have 2 pics! When I first looked there was a little box saying 'whatever the file-name was.jpg' and it wouldn't open. Now it's there in both your posts. Sorry!!

    I'd probably go for lead if the underlying brickwork is good enough to get a well-tucked joint.
    • CommentAuthortony
    • CommentTimeJul 10th 2011
    Cut a straight groove into the render just above the flare, then smack out the cement fillet. Add soakers, then a cover to the top of the soakers which goes into the groove and point in.

    It looks like the original design had "tilters" --------- also there are some slates missing in the body of the roof too.
    • CommentAuthorCWatters
    • CommentTimeJul 10th 2011
    How would this gap be sealed if traditional lead sheet were used?

    Lead soakers as Tony said. These are lots of individual overlapping bits of lead - one per tile..


    but instead of a stepped cover piece over the soakers use a straight one let into the slot cut in the render.
    I'd suggest the groove went into the brickwork beyond the render rather than just into the render itself, or there's perhaps more of a risk of water getting in from above via a crack in the render.
    thanks for your help. Do you think I'll find a tilter under the column of tiles closest to the chimney? Is a tilter in this case one long piece of wood to angle the slates away from the chimney / wall?
    • CommentAuthortony
    • CommentTimeJul 12th 2011
    yes and yes kind of
    put a piece of wood along the line of the roof to rest your angle grinder on - this will keep your line straight.
    I used one long piece of lead pushed into the slot, folded down and then across the battens like this:
    then tile/slate over the top. Please note I am not a roofer, builder, or plumber (as in lead work) so it may not be best practice.
    pack small bits of lead into the groove to hold it in place, then seal with LeadMate (I think its called) comes in a tube like silicon sealant.
    I always turn up and back the edge of the lead that is under the slates or tiles so that any water on the lead is contained on to the lead and can not run off.
    BTW lead flashing is unknown here. Aluminium is used, but being so far from the sea there is no salt in the air so corrosion is not a problem. Much cheaper but more difficult to DIY bend.
    • CommentAuthorfinny
    • CommentTimeJul 13th 2011
    Not sure about Doms system there.. we get a lot of rain around here and I would expect the tyvek to be keeping me dry!
    Get a traditional plumbers manual, all the leadwork techniques will be there..
    If you don't get your soakers and flashing right, your roof won't be up to the job :cry:
    • CommentAuthortony
    • CommentTimeJul 13th 2011
    Dom I love the look but I would always use soakers -- mine would look the same but wouldnt get the battens wet
    I'm afraid that I don't really agree with Dominic Cooney's suggested method. If you wish to form a 'secret gutter' (which is a neat, if slightly more complicated solution) the lead work should be set down into a vertically running tray formed between the wall and the ends of the battens. The gutter should also continue under the slates all the way down to the eaves and not finish at the end of the abutment wall.

    I know that there is always more than one way to do a job and everyone has their own preferences... But, I fear, that a flashing detail like this is going fail before very long. The Tyvek is simply keeping the water out at the present time.

    With regard to the original question, Tony's recommended solution of lead soakers combined with an over-flashing is the most straightforward solution.
    Dominic's solution would work, if the inside edge has a return as I suggested above and at the end of the flashing the flashing should come out on top of the last slate of the abutment wall thus any water on the lead will be taken to the outside of the slates and not on to the batons.
    • CommentAuthortony
    • CommentTimeJul 13th 2011
    It would possibly work without but not durably.
    • CommentAuthorCWatters
    • CommentTimeJul 13th 2011
    Posted By: Dominic Cooney I used one long piece of lead

    I wouldn't do it that way. Use invidual soakers as per..


    The idea is that each soaker is like an L shape tile. They are interleaved with the tiles so the water runs out onto the top of the tile below not down the roof felt.
    One long piece of flashing works here (aluminium as stated above) interleaved on to the outside if its not full length. This type of flashing copes with snow melt which can be sudden and summer down pours which can dump an inch or more in 30 minutes (our typical summer rain) This is much easier and quicker than individual soakers although I will admit that the soakers would be the traditional solution, probably stepped and set into the mortar lines rather than a groove cut into the bricks.
    • CommentAuthortony
    • CommentTimeJul 13th 2011
    A stepped flashing is in my opinion outmoded, inferior, not as effective and uglier than a simple cover fitted into a straight slot to cover the top edges of the soakers and hang down to just above the roof line giving the same appearance as the photo.

    This method saves on lead too.

    one likely reason why the don't use lead in central Europe is that it denatures oxidised at low temperatures!
    I could always put the soakers on later when I put the rooflights in (this roof is on phase 2 which may not be tackled for a few years yet!)
    I was expecting the tyvek to be waterproof - otherwise what's the point of using it? It should direct any rain/snow that gets blown between the tiles out over the eaves into the gutter.
    roofing membrane (Tyvek, roofing felt or any other sort) is supposed to be a secondary defence against the ingress of rain in the event of a slipped to cracked tile or slate. Its not a good idea to use it as the primary waterproofing agent on a roof - that is what tiles / slates are for. Its easy enough to interleave the last pair of slates to bring the lead and any water on it to the outside.
    If you are going to use the Tyvek as the primary waterproofing agent lower down the roof, why have the lead at all, just return the Tyvek up the wall a bit and cover with a fillet of cement to keep the UV off it. This would work just as well as leaving the lead under the slates and would save the cost of the lead. I would not do this!!! Apart from anything else the repeated wet / dry cycles that the battens would be subjected to would ensure they would not last long.
    So it's the battens really that are the problem, not the tyvek. The tyvek does actually go up the wall a bit under the lead. A cement fillet would crack way from the wall eventually and water would get down the crack, so definitely not a good solution. The lead set into the line cut in the stone and folded down stops this happening.
    I had considered a stepped flashing but with the stones being relatively large it would have looked ugly here.

    I will probably turn the edge of the lead back as P in H suggests when I fit the rooflights and direct it out over the last tiles as this should be straightforward to do retrospectively. Or maybe soakers if i can still afford the lead by the time I get round to it!
    • CommentAuthorJoiner
    • CommentTimeJul 14th 2011
    Can anyone explain why there is so much resistance to doing it the tried and long-trusted way it's done here in the UK? As per the link given by Cwatters! :confused:
    • CommentAuthortony
    • CommentTimeJul 14th 2011
    I would do the soakers like the link but stepped flashings are now history! They use more lead and more time than the simple covers let into a straight cut and look uglier.

    All of my last three points makes the historical method unsustainable, it is quick and easy to cut a slot these days.
    • CommentAuthorJoiner
    • CommentTimeJul 14th 2011
    Not in an old building, Tony. Your balls would be displayed on a pole on the chimney as a warning to others. :bigsmile:

    The photographs in the OP look to be of a VERY old building. :wink:
    Mine is 1834
    originally had just a mortar fillet against the wall.
    Also having looked at other buildings in the area, I think a cut slot looks much neater than trying to do a stepped flashing on large stone blocks of different sizes.
    Further to Dominic Cooney's comment..
    I will probably turn the edge of the lead back as P in H suggests when I fit the rooflights and direct it out over the last tiles as this should be straightforward to do retrospectively. Or maybe soakers if i can still afford the lead by the time I get round to it!

    I'm afraid that simply forming a welt along the outer edge of the lead will be insufficient to stop water spilling off the flashing onto the Tyvek and battens. This is because lead is unable to support its own weight, and over time, will sag down in the unsupported gaps between the battens directing any water onto the roof underlay. You may want to bear this in mind as my experience is that poorly detailed flashings can, over the long term, cause wet rot and potentially expensive damage to structural roofing members. No serious roofer will ever rely on felt, sarking, or underlay to prevent water ingress.

    Best wishes

    Afraid that I can't work out how to highlight other peoples previous comments .:shamed:
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