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Thread: My shed leaks

  1. #16
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    I second wimmera Jack, a soaker flashing that goes under the upper sheet and over the lower, with 200 overlap on each

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  3. #17
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    Something like this
    Consolidated Alloys 150 x 0.7mm x 10m Weatherflash | Bunnings Warehouse

    Or adhesive version Consolidated Alloys 100mm x 10m Weatherproof Byute Flash Flashing Tape
    If I can dress that around the profile, it should seal fairly well.


    Having a close look, if I lift the sheets, I can increase the overlap because the lower end actually projects a fair way over the last batten. That would of course either leave holes where the screws used to be, or require new battens. I suppose if I do that I can grade them a little more to increase the pitch.
    Just what I need... Another project...

    (The pitch is ~3 degrees
    The overlap is about 50mm except, perhaps perversely where the leak is where it is closer to 100 (a sheet replaced after a tree gave it a bit of a nudge). On close inspection there is a bit of a dent in that sheet, so the end may be flatter. Could explain the problem. (hazy memory, it was an insurance job, at a time when trades were in short supply for little jobs)

  4. #18
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    I was thinking more of something like this - Our Range | The Widest Range of Tools, Lighting & Gardening Products - nice and wide. There are other damp course products like this around, but Bunnings don't seem to stock them.

  5. #19
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    Thanks but that just links to a general page-no product...

  6. #20
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    Quote Originally Posted by russ57 View Post
    Thanks but that just links to a general page-no product...
    Works fine for me. Search 'Aldamp 350mm'.

  7. #21
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    Thanks aldav.

  8. #22
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    Default Just get a flashing made up

    For the cost of all that stuff from Bunnings, that may or may not work, it would be easier and cheaper and definitely more effective, to measure up the angle and get a soaker made at the roofing supplies shop, in the same material as the roof, in short (3 m) sections, take out the bottom row or two of screws in the upper roof, slide the flashing under it, and screws the upper roof back down, then you can cut the notches out of the flashing to key it into the lower roof, and either screw it or pop it to the roof. Job done.

  9. #23
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    All those Bunnings referenced products are not designed for the task, the aluminium dampcourse has a bituminous coating so you would need to use a compatible sealant to use with is and then over time the coating delaminates from the aluminium as it is not designed to be exposed to the elements and your seal will fail again.
    I agree with Riverbuilder that a custom made flashing would also be an option but you still need adequate turn up on the end of the sheets with such a flat pitch.
    From the photos provided that does not look the case but it can be difficult to judge from the photos

  10. #24
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    What sealant do you suggest the OP use with the custom made flashing? I've never seen a sealant used with the type of flashing you're suggesting, where the edge is cut down to follow the profile of the roofing sheets.

    I'm pretty sure the pictured flashing - FLASHING APRON VARIOUS COLOURS @ 3.1 MTR LENGTHS | eBay - is the type being suggested Russ and the pic. is a sample of how it's cut down on to the roof. But of course you can't buy a standard profile for your application, that's why you have to get one made. It won't be $15 for 3 metres.

    If the joint in your roof faces the prevailing weather I wouldn't consider the suggested action a permanent fix as dust and small debris is still able to be driven up under the flashing. The fact that your verandah roof has very little fall presents you with an ongoing problem. Even if the sealant on the aluminium damp course fails in time at least it can be resealed without having to pull the roof apart.
    Attached Images Attached Images

  11. #25
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    If he does an apron flashing and weathers the sheet ends he is not relying on a sealant but if he used a dampcourse ( alcor) the sealant becomes the primary seal

  12. #26
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    I wasn't suggesting that the end of the verandah sheets should not be weathered.

  13. #27
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    The greater the difference between the two pitches the longer the overlap should be. It is not only litter that causes water build up and back flow, it is also the different rate of flow down the two roof surfaces . The steep roof is delivering water far quicker than the shallow pitch can get it away. Whatever form of flashing is used it will require sealing under the lower edge to prevent capillary action.

  14. #28
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    I knew this was the right place to seek advice!
    The shed roof is quite small--5 feet horizontally to the Ridge. It faces north, up hill. The house is above the verandah, so it's pretty sheltered so no worries about driving rain. Thanks for pointing out the issues with different flow rates, very helpful observation..


    So if it needs to be sealed, and not just flashed with solid /profiled sheet, then I think my best course of action is
    A) turn up the sheet ends more
    B) flash with an adhesive aluminium
    C) keep the roof clean(er).
    Possibly not the absolute best solution, but I think it will solve my problem well enough. (bang for buck)
    is there some other form of sealing that would work (with solid, custom flashing)
    (and note I haven't suggested silicone at all although it did cross my mind...)




    I could increase the overlap but only by about 50-75mm at the most. Sounds like while that would be a slight improvement it won't actually overcome the issue. And I could change the gradient slightly but that would be a major job, and again helpful but not sufficient.

  15. #29
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    The simplest step would be turning up the sheet ends more if they are easily accessed. The internal corner of the profile is where the greatest risk of leakage occurs. A bead of sealer run continuously along the top edge of the turn up will help. A weather flashing would also be a good move.

  16. #30
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    Hi Guys,
    Having built many sheds over the years, I would suggest the simplest and most cost effective solution is to use a proper folded flashing.
    Have a talk with a steel supplier and see about having the flashing folded to suit about a 20° pitch. The photo below is with a 90° fold (arrow).
    The flashing cost should be around $15/m.

    Unscrew the bottom 2 rows of screws on the upper roof, slide the flashing up underneath the sheeting. Then mark where the trimdeck rises and cut out the sections with tin snips. Don't just cut each side and fold flat, this just invites corrosion between the flashing and the trimdeck.
    Lay everything back in place and pop-rivet the flashing to the trimdeck. Silicon and rivet the flashing joins (150mm overlap) as you go. Re-screw the upper roof sheeting back in place. Finally, silicon the rivet heads. Don't use any silicon in the tray of the trimdeck as this will stop any water that may find it's way in from getting out.

    Flashing.jpg

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