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What roofing sealant to use?

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  1. #1
    Timber Hoarder Cliff Rogers's Avatar
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    Default What roofing sealant to use?

    G'day.

    What's the good gear for roofing sealant?

    I want something that will stand up to UV & not react with the galvanisation & cause rust.

    I would be good if it could also be painted.
    Cliff

    ...if all you have is a hammer, everything looks like a nail...

  2. #2
    A Member of the Holy Trinity journeyman Mick's Avatar
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    Cliff, what specifically are you wanting to do? If you have a leak and you're trying to fix it with sealant it's only ever a temporary measure. All sealants break down with UV, especially up here. You may need to look at fitting some flashings to alleviate your problems. If you want a good quality paintable sealant any of the Bostik or Sika polurethane ones are good. If you give me some more detail I may be able to help you with a more lasting solution.

    Mick

  3. #3
    Timber Hoarder Cliff Rogers's Avatar
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    G'day.

    My main problem is water coming back under flashing due to shallow roof angles.

    We have a house on the tableland over between Milla Milla & Tarzali with a bullnose corro verandah all around. The slope on the verandah roof is very shallow so when it rains (a fair bit of the time) the water can get back up under the flashing & leak down the walls of the verandah. The ends of the iron has been turned up a bit from underneath but it doesn't stop the wind from blowing the water in over the edge.
    I want to go along & knock the flashing down a bit between the ridges of the corro & stuff some sealant under it to slow up the water running back. I may even have to take to the edge of the flashing with a pair of snips & cut a frilly edge on it so I can turn the edge down in between the ridges. The Sou-Easter doesn't help the problem at all either, the house in on the top of a ridge & faces ESE so when the big highs are crossing the east coast, our roof is trying to cross the west coast.

    Also have a new shed with skillions on both the long sides & the slope on the skillion is also very shallow. During a storm the other day, the wind blew the water on the roof back up under the overlap in the trimdeck where the roof meets the skillion & it ran down the walls inside the shed.
    I reckon if I attack that from the inside & stuff something like sicaflex into the gap in the overlap I'll stop that from happening.
    That one won't be exposed or painted but it will have to put up with a fair amount of movement as the trimdeck expands & contracts in the sun/shade.

    What do you reckon?
    Cliff

    ...if all you have is a hammer, everything looks like a nail...

  4. #4
    A Member of the Holy Trinity journeyman Mick's Avatar
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    Cliff, those "frilly bits" that your flashings are missing will go a long way towards fixing the problem. It's called scribing, after which you "dress" the flashing (thats a highly technical term for taking a bit of timber that fits nicely in to the trough of the sheet and tapping it with a hammer so as to push the flashing hard back against the sheet.) I tend to cut these bits slightly oversize so when they are forced back they seal real well. If you squirt a bit of sealant into the trough beforehand it should stop any water that does manage to get past. If fitted under the flashing like this it won't be visible (I assume) so silicone will be fine.
    On the other job a good neutral cure silicone will do fine, it goes on a bit easier than the polurethane sealants and is easier to tool. Good luck, hope this helps.

    Mick

  5. #5
    Timber Hoarder Cliff Rogers's Avatar
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    G'day again.

    Ta... now define "a good neutral cure silicone" in computer technician terms so when I go down to Tradelink I don't look like a computer technician that needs to be sold a carton of expensive @@@@.....

    I had asked a builder who did some renovations for me & he said "just get some sicaflex.... it's good @@@@"
    When I found a shop the sold it, there were about 9 different flavours & every flavour cost more than the job I wanted it for was worth. :confused:

    Thanks also for the info on the 'scribing'..... I have 34meters of flashing to scribe to fit corro iron.... guess where I'll be spending the next 15 weekends. :mad: You don't happen to be doing any work down our end of the tablelands do you?

    Now that you have reminded me, I do now recall the correct term for bending a bit of tin over.... I learned it in Grade 8 metalwork but that was 33 years ago so it had slipped my memory, temporarily.... umm, what was I talking about?
    Cliff

    ...if all you have is a hammer, everything looks like a nail...

  6. #6
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    Cliff.

    Nice part of the country up there.

    Neutral Cure silicone is the correct term.

    Most others use an acetic (smells like vinegar) acid cure which corrodes gal and aluminium over time.

    Just ask some owners of tinnies.

  7. #7
    Diamond Member Barry_White's Avatar
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    Cliff

    Another solution that is recommended by Lysaght is to use foam Infill Strip.

    If you go to Lysaght's or one of their distributors they will sell it to you. It comes in 905mm lengths and is designed just for that purpose.

    Just undo the screws and and push it under the flashing and screw it back down.

    From

    Ex Lysaght Rep

    See attached picture
    Attached Thumbnails Attached Thumbnails infill-strip.jpg  
    Regards Bazza

    Skype Username: bazzabushy

    "Experience is a hard teacher because she gives the test first, the lesson afterwards."
    -Vernon Sanders Law

    The views expressed by the poster are general in nature and any advice should be taken in this vein. The poster accepts no responsibility if this advice is used. When undertaking any work personal professional advice should be sought from suitably qualified persons in the field of work being undertaken.


  8. #8
    A Member of the Holy Trinity journeyman Mick's Avatar
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    Cliff, any brand name neutral cure (roof & gutter)silicone will do, I tend to avoid any "no name" brand stuff, however I'd guess that Tradelink probably won't sell the cheaper stuff. If you want to try and get the stuff a bit cheaper go to Cairns Hardware (or Tablelands/Mareeba Hardware) with daggy work clothes on, pay cash and ask for a written docket, they'll give you trade price. Also as an aside if you want anything from Carbatec, see the guys in the Cns Hwre tool shop, they'll sell it to you landed in Cairns for the catalogue price, save yourself the freight cost.
    Just had another thought before (I know, they don't come along very often ), on really flat pitch roofs where you have sheet overlaps water tends to get drawn into the space between the sheets (due to capilliary action) and stay there for quite some time. This will eventually rust the sheets out, I've had to replace sheets because of this. So it would probably pay to undo the row of screws on the overlap, lift the sheet slightly with the hook end of a pry bar or the back of a claw hammer, slip a couple of wedges in to hold the sheet up and apply a bead of sealant right along, maybe 20mm back from the edge. When you drop the sheet back down the sealant will squeeze out, pretty much to the edge, thus staving off the corrosion problems for quite some time.
    Tarzali? mate if I drive down there I'll be packing a picnic lunch and no tools! If you have some good wiss snips (my personal pick, my cousin also a chippy, prefers Prosnips but I can't stand em) and reasonably strong forearms you'll get it done in 2hrs or so. Have fun

    Mick

  9. #9
    Timber Hoarder Cliff Rogers's Avatar
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    G'day again,

    Thanks blokes, interesting looking stuff that Baz, have you tried it?

    Yeah Robbo, it's a great escape from Cairns in this wheather.
    It's very quiet & much cooler than Cairns.
    The downside is that it's a fair old drive to the pub/hardware/pizza shops after living in the middle of Cairns where we are walking distace to at least 50 pubs/clubs/restaraunts/pizza shops, Bunnies is 2 blocks away, Tradelink is 1 block away, Glenfords are 3 blocks away & Cairns Hardware is another 4 blocks down the road from them.
    At this stage, I live in Cairns 4 nights a week & up on the tablelands the other 3 nights.
    The other problem I have is the red dirt up there.... bloody stuff.... for every inch of rain we get, the grass grows a foot & we had 4 inches just over a week ago so I spent 6 hours of last weekend on a rideon mower.
    Here in Cairns the house is on sand & we had 11 inches last week but I can still string the mowing out til next week & then it only takes 20 minutes anyway.I get the best & worst of both worlds.

    Hey Mick I don't have any daggy looking work cloths down here so that means I can get out of the roof job for at least another week. The only snips I have are a big old pair of tin snips, big enough to cut elephant toenails & only good in straight lines so I guess I'll have to go to to one of my favourite "dress" shops again.
    Cliff

    ...if all you have is a hammer, everything looks like a nail...

  10. #10
    Diamond Member Barry_White's Avatar
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    Hi Cliff

    Yes I have used it in sheds especially under the flashings with translucent sheet and polycarbonate where you can't turn up the pans and as the picture says that it is used where you have windswept rain blowing up under the flashings.
    Regards Bazza

    Skype Username: bazzabushy

    "Experience is a hard teacher because she gives the test first, the lesson afterwards."
    -Vernon Sanders Law

    The views expressed by the poster are general in nature and any advice should be taken in this vein. The poster accepts no responsibility if this advice is used. When undertaking any work personal professional advice should be sought from suitably qualified persons in the field of work being undertaken.


  11. #11
    Banned Marc's Avatar
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    Hi Mick.
    I tried the dressing code trick in Harrison Moorebank and it worked a treat. I needed some 6"x1" Oregon and so I put on my worst rags.
    In the timber shed it did not help, because they left me to shoulder the timber and load it myself, but at the casher, I only needed to mutter the word trade mixed with other noises and voila, trade discount given.

    By the way, if anyone wants to buy 6"x1" decent almost dry Oregon they are selling it for $2.9 a meter and 2.5 if you go dressed in rags ha ha.

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