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Thread: garage roof with no rafter or collar ties.

  1. #1
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    garage roof with no rafter or collar ties.

    I saw a picture of a house for sale with a fairly new stand alone garage. Looked to be a 4 in 12 roof, 2 car garage with a standard looking ridge down the middle. The inside showed it had a very deep ridge board and no cross ties of any kind. It was rafters and not trusses.
    I have never seen this type of construction but I read it is not uncommon. You could even hang a light duty crane trolley under the ridge beam.
    Of course you have no attic storage.
    Bill D.

  2. My parents house was built like that back in the 1960's .If the is no ceiling of any kind below the roof to tie the walls together a crane of any kind below the ridge would be a bad idea

  3. #3
    If the ridge is of sufficient size there shouldn't be any problem. A lot depends on whether the building is where there is heavy snowfalls. The ridge would be carrying the entire load of the roof.

  4. #4
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    The whole reason for ties is to insure that the long-side walls don't buckle out with the weight of the roof structure and anything attached to it. I'd also be very hesitant to put any additional weight under that ridge beam for this reason alone. At the very least, I'd add some cable ties or hard ties across the structure at a few points even without hanging anything and that's whether or not there are gussets! The upstairs to my shop building has ties at four foot intervals and that's with a block wall structure below. I suspect that if it was stick built, there would be more support.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  5. #5
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    I guess that is how the so called cathedral ceilings are built. Seems like the walls have a lot of outward force on them. A real cathedral would have flying buttresses at the base of each rafter. I think it makes the gable walls a structural wall.
    Bill D.

  6. #6
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    As a carpenter that seems like a real dumb way to build. About twenty years ago I bought an old building for my first shop. I t had a roof like this with rafters that someone tried to make into trusses later. The walls had about a one foot bow out on each side and the roof had a sag as well. I bought some cable and added two across the building, it worked for about ten years until I tore it down and began to build my new shop.

  7. #7
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    Gable wall is the key. If the ridge beam is sufficiently supported by columns at each gable end (and possibly a center column), and of sufficient size (cross-section), it shouldn't sag. And so, the rafters can't drop with it - and so push out on the walls.

    But I do mean SUFFICIENTLY. Columns have to carry all the way to the foundation and NO deflection in the column or ridge beam.
    Molann an obair an saor.

  8. #8
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    Use a scissors truss. It does have the desirable load-carrying strength of a truss, but looks like an open v-shaped ceiling once you put the drywall on.

  9. #9
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    Rafter ties prevent the walls from spreading, collar ties prevent the roof from lifting and separating at the ridge line. Collar ties can be omitted when suitable rafter to ridge attachment methods are used. Omitting rafter ties requires more engineering.

    https://www.finehomebuilding.com/201...nd-rafter-ties

  10. #10
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    Quote Originally Posted by Malcolm McLeod View Post
    Gable wall is the key. If the ridge beam is sufficiently supported by columns at each gable end (and possibly a center column), and of sufficient size (cross-section), it shouldn't sag. And so, the rafters can't drop with it - and so push out on the walls.

    But I do mean SUFFICIENTLY. Columns have to carry all the way to the foundation and NO deflection in the column or ridge beam.
    This exactly correct. The ridge carries much of the load, much like a girder, and is structurally supported at the gable ends so it does not put downward force on the side walls causing them to push out. The key to this type of construction is sizing the ridge correctly and supporting it at the gables correctly. This method of construction is fine when done properly.

  11. #11
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    Quote Originally Posted by Mike Kees View Post
    As a carpenter that seems like a real dumb way to build. About twenty years ago I bought an old building for my first shop. I t had a roof like this with rafters that someone tried to make into trusses later. The walls had about a one foot bow out on each side and the roof had a sag as well. I bought some cable and added two across the building, it worked for about ten years until I tore it down and began to build my new shop.
    Do you remember how big was the ridge board?
    Bill D.

  12. #12
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    Our recently built house has a vaulted ceiling in the great room. It was originally designed with collar ties. As construction proceeded, they learned that we really didn't need them. We did them anyway just for looks.

    Ours are 1" steel rods with turnbuckles giving sort of an industrial vibe. We painted the steel black but left the threads and turnbuckles unfinished.

  13. #13
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    Oh Well the house sold in three days. Starting price was a clittle under 500 K. with about 1/4 acre.
    Bil lD

  14. #14
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    My workshop is built kinda like this with a ridge beam and rafters and then very little in the way of rafter ties at ceiling level. What rafter ties there were have the nails pulling out from the outward force. My roofline is a saddle and the rafters are actually bowing out the exterior walls slightly. It's.... not good. I'm actually looking at installing scissor style braces after the fact to make the ridge angle of the rafters more reinforced.

    In my main ceiling a previous homeowner had already cut out most of the collar ties wanting a cathedral ceiling and one structural engineer and 5k of steel plates later, it's better (or at least not getting worse).

  15. #15
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    Quote Originally Posted by Bill Dufour View Post
    Do you remember how big was the ridge board?
    Bill D.
    Just saw pictures online looked like about 4x14. All rafters had simpson clips top and bottom. I would guess not more then 24 feet long. It looked to be one of those beams made from strands of wood all compressed and glued together.
    Last edited by Bill Dufour; 10-18-2019 at 3:06 PM.

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