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Flashing on fibreglass roof on new garage failed in 2 years

Discussion in 'Roofing and Guttering' started by DB1203, 30 Jun 2020.

  1. DB1203

    DB1203

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    I had a new lean-to garage built two and a half years ago. It seemed to be a good job and I was very happy with it. (Only minor glitch I was aware of was that the roof has always ponded at the back, which is visible on the photo below but not related to the main problem).

    However, earlier this year, I was in the garage during a heavy rain storm and saw that there was water coming in in multiple places where the new garage roof meets the house wall. My first thought was that the flashing must have failed, so I contacted the builder.

    He came and had a look at it. The wall that the roof joins to has some old pebble dash on it, that the previous occupants put on about 40 years ago. His first story was that the reason for the leak was that the pebbledash had failed. But I can't see why the pebbledash makes any difference if the flashing is properly bedded into the wall behind, between the bricks and mortared in (as my builder says is the case). Also I can't see why it would have been sound 2 years ago but deteriorated to the extent that it is causing a leak now.

    I don't want to get into a technical argument about render and different types of flashing as I think it is not relevant - a new roof should last longer than two years, whatever it is made of. But am I missing something? And what needs to be done to make the flashing waterproof?

    Here are some pictures:

    [​IMG]

    This is a bit of the render that he says has deteriorated and caused the problem (it is like this in multiple places):

    [​IMG]
     
    Last edited: 30 Jun 2020
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  3. Alastairreid

    Alastairreid

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    Might be the roughcast, but my 1st thought would be the flashing not been channelled in deep enough.
    Does the roughcast sound hollow when tapped?
     
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  4. datarebal

    datarebal

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    A picture says a thousand words.
    Pebble dash looks fine. The flashing trim is not fitted properly
     
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  5. DB1203

    DB1203

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    It's firmly stuck to the wall. I tried to take some off once and it was not easy.
     
  6. DB1203

    DB1203

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    Thanks. That was what I assumed was the case as I couldn't see how water would get past otherwise.

    These are some more pictures of different bits. Does it look like the same issue? I'm trying to understand if it is just one problem bit of if the whole thing needs to be re-done.

    [​IMG]

    [​IMG]
     
  7. DB1203

    DB1203

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    So, I've had two roofers round to look at it.
    One said that it looked like it wasn't fixed in properly, and that he could re-seal it with sand and cement. The other one suggested adding an additional lead flashing on top of it. Not got a price for that yet, but maybe that sounds a bit overkill ?
     
    Last edited: 6 Jul 2020
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  9. Alastairreid

    Alastairreid

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    Better using sealant as sand and cement.
    2nd option is closer.
     
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  10. datarebal

    datarebal

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    Sounds the right thing to do IMHO
     
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  11. oldbutnotdead

    oldbutnotdead

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    That cover flashing doesn't look as if its been chased in properly. Wouldn't be a surprise if they've just chased into the pebbledash rather than going into the brick. Pull a piece off and have a look, its all got to come off anyway. There are also gaps in the mitring. Replace with lead is by far the best bet.
    The roof itself looks quite nice, hopefully you'll find correct upstands when you remove your test piece of cover flashing

    EDIT That ponding at the draining end of the roof isn't good, it looks as though the roof deck has sagged quite badly (which could happen if the OSB has got soaked due to failed flashing)
     
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  12. DB1203

    DB1203

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    Thanks for comments.

    The ponding has actually been there ever since they put the roof on. I mentioned it at the time as I thought it wasn't good to have ponding on a newbuild roof.

    They had two or three goes at fixing it but couldn't. I was a bit disappointed but it isn't much, and they clearly were not capable of fixing it, so I thought I would just live with it.

    It hasn't got any worse in the couple of years. However, I am concecrned that there could be rotting of the timbers so I'll keep an eye on it to check it doesn't get any bigger.
     
    Last edited: 6 Jul 2020
  13. oldbutnotdead

    oldbutnotdead

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    Thats a bit poor for a brand new roof then, if they'd done the deck and joists properly there wouldn't be a pond. Which makes it far more likely that the cover flashing isn't chased into the brickwork. Those GRP cover flashings are fine for modern straight flat walls but for corners you really need the proper corner pieces instead of mitring and lobbing sealant at it (which is what they've done).
    See how much the lead chap costs- you may be pleasantly surprised.
    Did the original builder offer any sort of guarantee- actually makes no odds, as you rightly pointed out a roof should last longer than 2 years.

    EDIT The tongue on c100 mock lead coverflashing is only 25mm. Your pebbledash is probably 20mm so no way are those trims properly fitted. I'm doing a bay window at the moment, pebbledash was between 20 and 35mm thick cos wonky brickwork. So I've cut a new chase 25mm into the brickwork and chopped the dash off below the chase. And its getting lead flashing- looks much nicer than grp & doesn't cost that much moree
     
    Last edited: 6 Jul 2020
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  14. DB1203

    DB1203

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    Interesting, thanks.
     
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