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RE: Advice on waterproofing timber frame for cantilever balcony

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  1. #1
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    Default RE: Advice on waterproofing timber frame for cantilever balcony

    Hi,

    I'm wanting some advice about waterproofing and protecting the timber balcony frame out the front of my new build.

    I would like to protect it from rain and water damage, and would like to make sure it lasts for at least 30 years.

    It faces west so gets a lot of sun in the afternoon and the house is located in Melbourne.

    I was planning to use a timber decking material on top, so the water runs through the gaps, but the timber beams would not be protected and I'm sure would rot over time.

    I was thinking I could have my plumber cover all the timber beams with metal flashing to protect it. Maybe shape it around the beams and seal it up and then screw the timber decking on top.

    What do people think? Is there a better way to do it? Any advice appreciated.

    I have attached a photo to show the balcony timber framing.


    Thanks Angelo
    Attached Thumbnails Attached Thumbnails 20181105_113912_small.jpg  

  2. #2
    Community Moderator phild01's Avatar
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    I use Alcor bituminous alumium flashing with great success. Don't favour the PVC stuff like Protectadeck.
    However my experience is with gal fasteners rather than stainless steel.

  3. #3
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    Thanks for the reply.

    Not sure if I was totally clear, but my plan was to completely cover all the timber beams, not just the tops, So they wouldn't be exposed at all to the weather.

  4. #4
    Community Moderator phild01's Avatar
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    Quote Originally Posted by angedac View Post
    Thanks for the reply.

    Not sure if I was totally clear, but my plan was to completely cover all the timber beams, not just the tops, So they wouldn't be exposed at all to the weather.
    Unnecessary, use H3 timber.

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    Agree with phild01, I use the same stuff and it works fine. Its wider than the joists so I bend them slightly downwards and that lets water flow off.

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    OH also, you could paint the wood in addition to the flashing which is what I did with my deck, but only to make the wood not so noticeable through the decking gaps.

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    I used H3 LVL timber for most of the beams as you can see from the photo(not painted) but the builder I think used H2 coming out from the house, these are black one . I painted them, to give them some temporary protection.

    I know over time the H2 timber will rot and I just wanted to avoid that.

  8. #8
    Community Moderator phild01's Avatar
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    I would choose a waterproofed tiled deck for that if the supporting beams can take a bit extra weight and can accommodate a screed.

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    It should be able to take the weight. I was just looking at other ways so I could use timber decking on the top instead.

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    As a minimum you would need to waterproof the joint between the front beam and the the joists - that’s the gap that rots first. Any protection of the top has to be pierced by fasteners when screwing a deck down.

    you could prime then paint with a UV stable waterproofing for outdoor decks , then also cover with protectadeck type rubber along beam and also along joists - this gives an element of allowance for a primary failure in protection

  11. #11
    Community Moderator phild01's Avatar
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    I have some concern about effective screw holding of the boards into the lvl grain.

  12. #12
    Senior Member DEMAK Timber's Avatar
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    Check out G-Tape! Japanese designed and going nuts over in the USA. We're now stocking it here in Aus...

    Has some magic voodoo in the adhesive that makes it rebond to any metal fixings that go through it to give a 100% waterproof seal.

    More info on the videos tab here: http://bit.ly/g-tape

    (Sorry if that came across a bit sales pitchy, we just love new stuff! )
    DEMAK Outdoor Timber & Hardware

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    The G-Tape looks good, but I don't think I could could I use it to waterproof the sides of the joists and beams. Looks like it's just good for the tops.

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    Senior Member DEMAK Timber's Avatar
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    Quote Originally Posted by angedac View Post
    The G-Tape looks good, but I don't think I could could I use it to waterproof the sides of the joists and beams. Looks like it's just good for the tops.
    You can use it on the sides too, it comes in 50mm, 100mm, 150mm, 225mm, and 300mm wide rolls. Just starts to get very expensive, very quickly....

    A much cheaper alternative would be Gripset Betta bitumen rubber membrane that you paint on.
    DEMAK Outdoor Timber & Hardware

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    I have looked into using that product, but the problem is it is not UV resistant.

    Overtime it powders up and comes off. I have already used this product painting some of the timbers in the balcony. (they are the posts coming out of the house and are black in the photo). I thought it would be UV resistant, but it isn't. I have confirmed with manufacturer and can see it coming off now.

    I'm looking for something that is more permanent.

  16. #16
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    Quote Originally Posted by angedac View Post
    but the builder I think used H2 coming out from the house, these are black one .
    instead of "I think" perhaps you should clarify with the builder?

    H2 is NOT rated for external use, why would the builder have used it in that situation?
    freedom of expression freedom from consequences...

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    Made in Japan? SOLD!

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    Quote Originally Posted by angedac View Post
    I used H3 LVL timber for most of the beams as you can see from the photo(not painted) but the builder I think used H2 coming out from the house, these are black one . I painted them, to give them some temporary protection.

    I know over time the H2 timber will rot and I just wanted to avoid that.
    You sure it's H2? What did the engineering plans say?

  19. #19
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    Yeah, pretty sure. I read it on the timber.

    Going back to my original question. Has anyone used metal flashing to cover balcony timbers or will a liquid sealer work? Does anyone recommend any products to use that would weatherproof the H2 timbers? Something they have used for exterior, that is UV resistant.

    I might consider using the G-Tape for the tops it looks like it will seal the hole made by the screws on top.

  20. #20
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    you really don't care that the builder used the wrong materials?
    freedom of expression freedom from consequences...

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    Quote Originally Posted by DavoSyd View Post
    you really don't care that the builder used the wrong materials?
    Maybe the original design (which may be different from the buyers intent) was to fully encase the balcony structure.

    OP. personally, I wouldn't do a high open deck surface if this is in a position where people use the underneath, due to debris and drips. Not sure that is the case here.

  22. #22
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    Quote Originally Posted by r3nov8or View Post
    Maybe the original design (which may be different from the buyers intent) was to fully encase the balcony structure.
    oh, right, yes, i can see how that would happen.

    there's no solution except to properly prime the timber and paint with exterior paint and maintain the paint over time.

    boxing it in with metal flashing will only magnify the potential for water to stay around and cause decay - you want the water shed & dispersed as rapidly as possible.
    freedom of expression freedom from consequences...

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    Quote Originally Posted by DavoSyd View Post
    .. you want the water shed & dispersed as rapidly as possible.
    Yes, agree with you here.

    Would it be worth painting them first with a Tar based sealer (or external waterproofing) and then go over it with exterior paint instead? Would that preserve it better?

  24. #24
    1K Club Member DavoSyd's Avatar
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    when i did my balcony, i cut everything to length, then I 'seasoned' the H3 timber (let the preservative air off), then i painted with high quality primer (Haymes Ultralock) then i top coated in two coats of high quality exterior paint (Haymes Solashield) then installed, i made sure to touch up the cut/nailed/screwed areas with Ecoseal Tanalised Timber Treatment then re-coated all cut/nailed/screwed areas with primer then two topcoats.

    i also painted the galvanised framing brackets with Norglass Norust and top-coated with exterior paint prior to installation and used Protectadeck on all the joists.

    but i was starting from a fresh slate - you have a work i progress situation, which is the complicating factor...
    freedom of expression freedom from consequences...

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