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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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    • CommentAuthortony
    • CommentTimeDec 26th 2020 edited
    Been there ten years now, no leaks, no falling down


    How is it sealed against the wall?

    It now has a cedar t&G ceiling, zero maintenance apart from clean the gutter and cobwebs
    I remember this quiz the first time around! But I can’t remember what the detail was in the end. I have a similar roof join (single storey kitchen to 2 storey barn) which I thought I had properly flashed with lead etc but is leaking so I need to look at it again when the weather picks up a bit. It’s worst when it’s windy.
    • CommentAuthorowlman
    • CommentTimeDec 27th 2020 edited
    Posted By: tonyBeen there ten years now, no leaks, no falling down

    https://www.dropbox.com/s/fvpm7gh2tespz75/Porch%20.jpg?dl=0" rel="nofollow" >https://www.dropbox.com/s/fvpm7gh2tespz75/Porch%20.jpg?dl=0

    How is it sealed against the wall?

    It now has a cedar t&G ceiling, zero maintenance apart from clean the gutter and cobwebs

    A. Secret gutter cut into the brickwork below the roofline.
    What's the odd looking wire/pipe coming out of the bottom left? Where's the gutter at the bottom edge?
    • CommentAuthortony
    • CommentTimeDec 28th 2020
    Paul, That pipe is one everyone should have, it is the drain down from my solar hot cylinder, now hidden and protected in the gutter.
    • CommentAuthortony
    • CommentTimeDec 28th 2020
    Owlman, no lead secret gutter this time, could work though
    Brown window mastic
    • CommentAuthortony
    • CommentTime7 days ago
    Takes the biscuit, brown yes, not mastic, but how can you tell?
    Because it is what I would do in a similar situation without cutting into the brickwork.

    If you dont cut into the brickwork, what else can you do except use a sealant?

    And therefore it has to be a non drying mastic if it will last the test of time.
    What is sealed against what, exactly?
    • CommentAuthortony
    • CommentTime3 days ago
    Wall to tiles so no water can get in
    I'd imagine that to be a very irregular kind of gap to try and fill with a sealant. Have you done it with mortar?
    Anything that dries will eventually crack, especially on a new build.
    Posted By: bot de pailleAnything that dries will eventually crack, especially on a new build.

    Yes, that's what I'd have thought.
    • CommentAuthortony
    • CommentTime3 days ago
    Would you expect what i have done to last ten years? I didn't use mortar though the Victorians did
    Victorians expected to live in cold, draughty, leaky buildings. A leaky roof was a luxury!
    • CommentAuthortony
    • CommentTime3 days ago
    I don’t think their roofs leaked and low cost solution was tilting fillet at the chimney abutment simply mortared to the bricks, some still not leaking after best part of 100 years

    Thinking mine won’t leak for 100 years either
    I'm confused... have we been told the answer or are we still guessing?
    • CommentAuthortony
    • CommentTime3 days ago
    What I did was to always have an original tile tight against the brickwork, starting with an eaves tile and I polysulphide masticed the tile to the brickwork. Then when the mastic was sufficiently dry I put the next tile and a half on but only masticed the top part of the tile that is hidden and so on, tile, tile and a half etc, took a few days but I was there for 163 days so no problem. None of the sealant is visible, it is protected from uv light. It hasn’t leaked yet. The tiles are so well stuck to the wall that I can’t see it ever leaving.
    I see; that's a neat approach as long as you are confident the sealant will do its job.

    Would you be confident enough to use this detail where there was interior living space below, and it was in the western highlands of scotland or wales?

    Raises another question for me, which also came up when I was looking at "secret gutter" details for this kind of situation recently.

    Obviously the standard detail would involve some kind of lead flashing that would rise above the surface of the roof tiles. There's the universal principle of flashing rising 150mm above the surface at abutments like this (I know that is reduced to somewhat less than 150mm on some leadwork details).

    My understanding is that one function of this 150mm protected zone, is to protect the wall from water that splashes up from a horizontal or sloping surface, and onto the lowest portion of the wall it abuts, when it's raining hard. Thus protecting it from damp. That protection is absent here... and I wonder if there's any evidence at all of that bit of wall getting more damp than the rest of it.

    It would especially be an issue where nothing is actually flashed *into* the wall, because it's not just about that local bit of wall getting damp, but about the dampness transmitting downwards within the brickwork. Even if your sealant works perfectly in stopping any water running down the surface of the wall, it can't do anything about this issue.
    We have a Victorian roof with cement fillets (haunch) where the slates meet the chimney breast. The fillet eventually cracks and leaks, due to effect of sunshine and frost - don't ask how we know this :-(

    The Victorians intended that the fillet should be replaceable every now and again when needed, so the cement was placed above the slates where it is accessible.

    Higher-status buildings had lead instead of cement, the lead wrapped underneath the slates as it didn't need to be replaceable.

    Hopefully Tony's polysulphide will last for the lifetime of his building and never need replacing! I'm sure that if the Victorians had polysulphide they would have used it everywhere, they liked innovation.
    Yes, I have a victorian roof with mortar haunches, and it's one of the points where the roof is liable to leak. I've already replaced one run (where there was significant water coming in during heavy rainfall) with proper lead step flashing and intend to do the other bits eventually too.

    The bit I replaced already was where it meets the chimney and this was the worst, because the chimney face has sufficient area to collect a fair bit of water. The other locations, it's just a small parapet upstand, with a sort-of drip detail at the top, so much less water has a chance to gather.
    • CommentAuthortony
    • CommentTime2 days ago
    In my porch no wood touches the wall with my detail and the loft void is uninsulated and unventilated

    All bricks can get wet, the more and harder it rains the wetter they get, splash increases it but even in absolute deluges no water comes in the porch nor any of the walls which do get wet, I have lime in my mortar
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