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rafter extensions for a bullnose

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  1. #1
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    Default rafter extensions for a bullnose

    I'd really appreciate ideas/comments from others:
    I have an 1800 wide bullnose roof, atop a norh facing timber framed external wall which ends with no overhang ie gutter attached to the wall. 120x35 pine rafters at 8 deg pitch at 1200 Ctrs. I am installing outward opening bifolds (850/panel) and want to give them weather cover.
    Suggestion so far have been:
    1. replace bullnose sheeting with single pitch roof, using rafter extensions to give overhang of 900 (BUT brings unsolvable(?) problem of how to weather the flat roof line up against a hip, the other side of which the roof continues as bullnose)
    2. add rafter extenions and lay with flat roof sheeting, keep bullnose and just flash onto flat sheeting.

    A. Any other ideas/comments on 1 & 2 above ?
    and
    B. how is the length of overlap (with existing rafter) calculated to enable an overhang of 900mm?

    Many Thanks

  2. #2
    Oink! Oink! pawnhead's Avatar
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    Either of those methods would look like a dogs breakfast I'd imagine.
    I take it that it's a queenslander that's had the verandas enclosed?
    How wide are your bifolds, and where will they be located?
    What's the pitch of the main roof above?

    Post some pics if you can.
    Cheers, John

    Short Stack (my son's band)


  3. #3
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    See pics - not a Qlder - approx 15 yr old, kit home I think.
    Bifolds are 5100 wide, and will replace aluminium window and door, opening onto pictured verandah.
    Along the back, the bullnose is 1800 wide.
    Top roof pitch is ~12 degrees.
    thanks alot
    Attached Thumbnails Attached Thumbnails dscn4312.jpg   dscn4313.jpg   dscn4314.jpg   dscn4317.jpg   dscn4318.jpg  

    dscn4319.jpg  

  4. #4
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    I could be wrong, but I think it's a lot more than 15 years old.
    To me it looks like it's been attacked several times in its life, extended, renovated, verandahs closed in, etc. culminating in a reclad, new windows, and a new roof. It's not a homologous design at all in my eyes, and I very much doubt that it was designed that way in the first place. Take this shot for example. It looks like a butcher has attacked it. The outside wall steps out as the second floor cantilevers over. The balcony beam is bodged up over the roof below, and there’s a dogleg in the wall above. The drainage looks lika a bit of an afterthought as well.
    And BTW, it looks like that balcony post is split and rotten at the bottom. Being an upper floor balcony, I'd give that some attention.

    Given the steeper roof pitch at the front of the house, as shown here, my guess is that it’s an old single story queenslander with wrap around verandahs, who’s original main roof pitch was the same front and back. Then someone has come along and lifted the roof at the back and put an upper floor extension on, and enclosed the verandahs here and there with no particular attention to overall aesthetics. You might as well just put a cantilevered flat roof over your new bifolds, and have a flashing bodged up to waterproof the junction at the bullnose, or redesign the back of the house to make it homologous.

    Here’s a compromise solution that wouldn’t look too bad IMO:



    Of course it’s more expensive than just bodging something up, and of course you'd install the doors the right way up, and your weatherboards level.

    I’ve shown a gabled roof out over the extension below, and extended the deck, and the wrap around bullnose past that. You'd design the pitch of the gable so that it would clear the bottoms of the windows in the upper storey above, and I reckon it would be about the same as the pitch as the top story roof at the back. With this idea, you could also install bifolds that were taller than a standard height as well. I've just built bifolds at my place that are 2.5 high and they look great.

    If you don’t like the idea of a post in the middle of the deck, then you could extend the gable out further over the deck so that the bullnose ends up at the edge of the deck. This would give you a completely covered deck with the posts along the edge, and you’d need a post at either end of the gable, but there’d be a clear span the full width of the room.
    I could illustrate this idea if you wanted.

    It's still very non symetrical with the bullnose being cut off square at one end, but the whole house looks a bit hotch potch to me, no offense.
    Cheers, John

    Short Stack (my son's band)


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    Wow - thanks very much for the illustration!
    What application do you use for this?
    Thanks too for offer to do picture of larger gable - no need at this stage.
    Agreed, that the rear of house looks very cobbled together.
    And balcony post due for attention amongst the coming project.
    However am confident/definite about vintage - was never Qlder / reno'd - kit home must've had some optiosn that previous owner/builder buggered around with. Have attached (old) snap of front FYI (brick veneer on base of three levels at front).
    Cheers
    Attached Thumbnails Attached Thumbnails front.jpg  

  6. #6
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    Quote Originally Posted by sprig View Post
    Wow - thanks very much for the illustration!
    What application do you use for this?
    Photoshop. Well, not photoshop, just the manipulation program that came with my cheap camera. The ‘Gimp’ is supposedly almost a clone of photoshop and it’s free.
    I basically just open two copies of the photo, and I work on one, whilst I cut pieces out of the other one, and manipulate them before pasting them on the working copy, eg I cut a piece of fascia, twist it to the right angle, then paste it as a barge board. If it’s not long enough, then I hit paste again and slide the two pieces on top of each other to get the right length. I cut out the bullnose corner, and slide it forward. I grab a piece of decking, and keep pasting it until I have an area covered, and ditto with the cladding. I cut a piece of post, and keep pasting it untill it's long enough, and I've done all three (those posts are a bit bulky and I should have re-sized them). I use a blurring tool to merge in any visible joins. I grab a set of bifolds from Google image search, re-size it if it's too big or small, and I paste it into MS word to stretch or squeeze it if needed, then take a screen capture. If I need to add diminishing perspective, then I display it on my screen full size, twist the screen, and take a picture with my digicam. The Gimp would allow you to do that stuff without farting around with a camera or MS Word, but I couldn’t be bothered learning it. I’m pretty quick at it, and if I spent a few hours I could make it just about photo realistic, with shadowing (darkening/lightening tool) and all, so you could hardly pick it from the real McCoy.
    Quote Originally Posted by sprig View Post
    Thanks too for offer to do picture of larger gable - no need at this stage.
    Not a larger gable, just extended further out over the deck. And you wouldn’t need posts to support it if you threw some engineering in, but that would cost a bit. What I’ve shown there wouldn’t cost a great deal if you did it yourself. You’d re-use the existing bullnose, hip, and guttering, and just buy three more lengths of bullnose to bring it out a bit more. You’d cut the gable cladding out of the house wall before you throw up a few rafters, and you’d re-use it in the new gable. Then just buy straight roofing sheets to put on top. If you had four trusses made up, with the outside one designed to carry the weight of the bullnose roof and your doors, then you wouldn’t need to put a monstrous beam over your doors to carry that five metre opening. The gable should have a bit of an eaves overhang to match the sides, and you could put a nice finial on top to match finials you've got at the front of the house. A gable vent might give it a bit more character, but that may be a bit of overkill with a finial in front of it.

    There's some pics of the bifolds that I built for this place in this post if you're interested. They're six leaf, 2.5 high and 4.6 wide in total, and they're unique (as far as I know) in that when opened fully, they fold right back flat against the outside wall, instead of sticking out perpendicular to it like all other bifolds that I've seen.
    If you had a bit of nous, you could do the same thing. You'd only have to slide your bullnose out by a foot to cover the doors, but you could put a wide flashing against the house, and slide the hip forward a foot, then buy just one sheet for the gap created. You wouldn't have a great deal of weather protection with only a foot of eaves overhang though.
    Quote Originally Posted by sprig View Post
    Have attached (old) snap of front FYI (brick veneer on base of three levels at front).
    Cheers
    Wow that’s a great looking house from the front. I suspected that there would be some nice dormer windows upstairs there.
    Very impressive.
    Cheers, John

    Short Stack (my son's band)


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