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Strange roof - anyone seen this?

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  1. #1
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    Default Strange roof - anyone seen this?

    Hi all,
    this is our home we just bought.
    I want to knock down some walls, obviously need to get things inspected by an engineer, but this roof line/type has got me stumped. Doesn't look like there are truss's like my current home, and the plaster in the roof follows the roof line, kind of like cathedral ceilings, but not so cathedral.

    From my inspection, its like the walls are holding the roof up!! I have seen this in almost every home in the area, and was a standard back then, or what looks like to be a standard design...

    So anyway, how does a roof like this work? and do u think I am going to have alot of trouble taking walls down etc..?

    Cheers
    Attached Thumbnails Attached Thumbnails roof1.jpg   roof2.jpg   roofoutside.jpg  

  2. #2
    Oink! Oink! pawnhead's Avatar
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    Quote Originally Posted by oohsam View Post
    From my inspection, its like the walls are holding the roof up!!
    In most houses the walls are supposed to carry the roof, unless the roof is fitted with skyhooks.
    In your case they've just lined the underside of the roof rafters and skipped the ceiling joists. It's not a big house and the spans aren't that great.
    Any walls running in the same direction as your ridge (From the front to the back of the house), would be supporting the rafters, and you'd need to put a beam in if you wanted to remove them. Any walls running perpendicular (from one side of the house to the other), probably aren't carrying anything, but they may be providing some bracing.
    It's not a big house though, and there'd probably be enough bracing in that direction, just in the two end walls and the section in the middle of the house, next to your front door where the meter box is.
    An engineer would know better after a site inspection though.

    What walls do you want to remove anyway?
    If it's nothing too drastic, then I'd probably just do it without any consultation if it was my place. That would be your call though, and my advice would be to get an engineer.
    Cheers, John

    Short Stack (my son's band)


  3. #3
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    Thanks for the reply pawny!
    I want to remove the wall in the first picture, open up that doorway, and that ugly thing in the kitchen...
    there is also a wall in the bathroom, but that shoudl be fine cuase its very small and runs the same direction as battons would...

    I will get a buidling inspector in anyway to check the stumps and structure etc, anyway will ask them to assess at the same time...

  4. #4
    Oink! Oink! pawnhead's Avatar
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    Quote Originally Posted by oohsam View Post
    Thanks for the reply pawny!
    No wuckers.
    This one’ll cost you a greeny.
    Quote Originally Posted by oohsam View Post
    I want to remove the wall in the first picture, open up that doorway, and that ugly thing in the kitchen...
    there is also a wall in the bathroom, but that shoudl be fine cuase its very small and runs the same direction as battons would...
    That’s a good idea. It will really open the place up. It looks pretty cramped in there. I’m pretty sure you could pull that floor to ceiling cupboard out with no problems.
    It’s hard to tell exactly how big it is from those distorted perspective pics, but I’ve made some guesstimations and done a sketch of what I think your roof structure looks like, and what I might do if it were my place;

    I’d get the measurement of my spans in both directions (NS & EW), and find out the load; plasterboard + whatever timber + asbestos or tin. The pitch is too low for tiles I'd say. Look up LVL Hyspan tables (Hyspan: Span Tables for residential building, 1Mb pdf), and select the appropriate beam.
    Steel would be smaller, and probably more expensive. I could calculate the steel, but only an engineer is permitted to certify it.
    At the moment the rafters over your dining room would be cantilevering over that wall, and supporting the rafters that come from the other direction (over your lounge room). It looks like the ceiling becomes lower in your kitchen than at the opposite side in your lounge room, since your lounge room steps in by the width of your front steps.
    There would be a ridge board that may be only 3/4” thick, or it may be semi-structural at 3” thick or something. Your rafters look like they may be only 4 x 2s, but your ridge may poke up past the rafters up to the underside of your roofing, flush with the top of your battens.

    It would be easiest to prop the roof in the lounge room near the ridge (with a plate on the floor to spread the load, unless the prop is directly over a joist), on the dining room side, then remove the wall, and install a beam underneath. But then you’ll have a beam sticking down in an awkward part of your ceiling.
    I’d prop it on the other side of the ridge, remove the ceiling lining on the narrow side, remove at least a foot of the ceiling lining on the other side, and cut the rafters away from one side, allowing for the thickness of the new LVL. Remove the old ridge, and slip the new LVL in its place. Nail with 3 x 3” nails skewed in from the rafters to the beam. Install joist hangers or at least two universal framing anchors (with a tongue bent up under the rafter and fixed from underneath) on each rafter beam connection. Then either line the beam with plasterboard, or install trimmers between the beam and the rafters, flush with the bottom of the beam and level. Then you’d have a flat section where the ridge used to be, and you wouldn’t see the beam at all. You can see the line on the drawing, in between where I’ve written ‘New’ and ‘Ceiling’.
    That’s a lot more work, but it would look better IMO. You could only do it, so long as the rafters in the kitchen didn’t become over spanned by extending their load up to the new ridge (although with trimmers in place, they act as a brace across the peak of the roof, technically reducing the span). They might be over spanned already in an old house like that. The standards have tightened. Ford Timbers have span tables on line (Roof Framing 157kb pdf). Find out the size of your rafters and battens, and the pitch of your roof, then you can work out how much of the beam will be below the bottom of the rafters, and how wide the level section would be.
    It would be easier to put the beam underneath, but then the level section would be lower.
    A beam at the ridge would have to be longer and larger as well though (because of the dog-leg in the outside wall there, looks like about a metre), so it may not be worth it.

    If it’s cavity brickwork, I’d cut/chop a hole in the inside skin, and run the beam the full width of the brick, and pack it with fibro or grout. If there’s a parallel wall supporting it on the other end, I’d run it so it has at least 150mm support. I'd run hoop iron over the top, and down each side, fixed along a dozen courses down the brickwork (chopped into the render). If it’s brick veneer with a timber framed floor, I’d get under the floor and inspect what’s directly underneath the ridge. If there’s no pier there, then I’d measure where the nearest piers are on each side, and make sure they are packed directly above them, right up to the underside of the wall. Then I’d go back upstairs, and I’d cut a slot in the wall under the ridge, from floor to ceiling (It looks like the position of the air conditioner may be a problem). I’d cut it 10mm overlapping the two adjacent studs, and I’d try to get the plasterboard off without damaging it too much. I could replace it, using the same studs, without any trimming. I’d install the appropriate beam (I’d probably order the LVL a bit longer, and allow the off cut for this beam), on top of the bottom wall plate, from pier top to pier top. I’d then insert a 4”x4” post between the new ridge beam, and the new beam at the floor, and cleat a 4”x2” on each side of the post (I'd use the studs from the wall that's been removed), running up past the beam, and fixed to it through packers, with framing anchors and hoop iron for tie down. I’d cut and reinstall any noggins I’d pulled out, and I’d replace the plasterboard, patch up holes, perhaps with the plasterboard that came off the wall I demolished. I might even pull a few studs out of the old wall first, and use them to prop the ceiling. I'd use them for any trimmers and noggins I'd need. After patching the floor, tape and stop the plasterboard, sand and paint.

    Then I’d crack open a beer in my new open plan lounge/dining/kitchen.


    Quote Originally Posted by oohsam View Post
    I will get a buidling inspector in anyway to check the stumps and structure etc, anyway will ask them to assess at the same time...
    That’s a good idea, and after it’s been specified by someone, you’ll have an idea of what’s involved if you want to tackle it yourself, then get it certified. An engineer may well come up with ideas involving fabricated steel columns and beams, but timber would be cheaper and easier. They may not even suggest putting the beam in place of the ridge, but I’d put the extra work in if it were my joint.
    Someone has to find out what's up there, what your walls, floor, and roof are made of, and measure your spans.
    Happy to answer any more queries.
    Cheers, John

    Short Stack (my son's band)


  5. #5
    Senior Member PlasterPro's Avatar
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    Quote Originally Posted by oohsam View Post
    Hi all,
    this is our home we just bought.

    Cheers
    This house looks like many in my old area with the post code 3200 or 3199

  6. #6
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    Good lord pawnhead, you really went to town on this! Talk about being specific. You never cease to amaze me old friend! Great source of info.

    This has given me much more confidence. Will let u know how I go after the building inspector sees the house...

    Now to find a building inspector!

  7. #7
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    Now that's what I call a great indepth answer
    Brilliant!!

    Regards Bradford


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