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Thread: porch bracket - structural

  1. #1
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    Default porch bracket - structural

    Question

    We are adding a small entryway roof 6' wide projecting 4' from house and want to use something like the brackets shown below.

    I have seen a few sites that mention that these brackets are not structural which does not help me out. I'm guessing the non-structural ones are just screwed together with no mortise/tenon at all.

    I'm thinking it would be pretty easy to make from 4x6 cedar or fir and if you notch in the shouder (not sure if this is the right term) it would support the weight just fine.

    Thoughts ?

    Pete





  2. #2
    Join Date
    Nov 2006
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    Default Re: porch bracket - structural

    Pete, those brackets could probably support some weight, but not much, no matter how they're joined. The weak spot, as I see it, is the upper inside corner. any load will want to separate the joint here, and it would be difficult to make a connection of sufficient strength on the ends of those two pieces.

    I think that these kinds of brackets are meant to imitate a situation where a horizontal beam, such as a girder,extends through a wall, cantilevering a few feet outside the building. The diagonal bracket then only has to support the end, as no amount of force could pull the beam away from the building. You can see this sort of thing in medieval timber frames where the second story overhangs the first, sometimes with brackets, sometimes not.

  3. #3
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    Default Re: porch bracket - structural

    Jim raises a good point but I do wonder if a pinned tenon here could be sufficient.

    Rather than notching in the diagonal (as on the left-most of the small pictures) I would think that tenons here would be much stronger. If you just notch in the ends of the diagonal then the load is trying to split off a thin strip of the vertical and horizontal members, which would not take much load. A tenon, possibly with the ends also notched in, would be stronger.

    What you really need is a timber-framer who would know how much load the different types of joints can handle.

  4. #4
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    Default Re: porch bracket - structural

    What sort of wind loadings do you get in your area? The strength of roofed open structures is as much about holding it down as up.
    There is nothing quite as permanent as a good temporary repair.

  5. #5
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    Default Re: porch bracket - structural

    A bit dark for photos right now but we did something similar about 20 years ago and the roofs are still in place. Front and back doors are the same. Our roof is maybe a bit narrower but does project about 4 feet. I used cedar 4X4's and notched the angled piece in as you have suggested. The one thing different really is that the verticle piece runs further down the wall.

    Will provide a photo or two tomorrow if I can.

    Randy

  6. #6
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    Default Re: porch bracket - structural

    The way that the roof parts above the bracket tie into the existing wall/roof is as important as the bracket.
    If it attaches to a wall,the first pair of rafters should be well fastened with big lagscrews and the whole mess sheeted with plywood.
    R
    "Now Ron,don't you do anything stupid!" - Grandma B.

  7. #7
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    Default Re: porch bracket - structural

    I have been working on a 200 year old house with balcony brackets like those pictured. They are notched and morticed and tenioned and pinned. They have been exposed to the weather for at least 30 years since the house was abandoned. The joints are still too tight to admit a knife blade. Just no sign of movement.

  8. #8
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    Default Re: porch bracket - structural

    Quote Originally Posted by ssor View Post
    I have been working on a 200 year old house with balcony brackets like those pictured. They are notched and morticed and tenioned and pinned. They have been exposed to the weather for at least 30 years since the house was abandoned. The joints are still too tight to admit a knife blade. Just no sign of movement.
    What are they supporting?

  9. #9
    Join Date
    Jun 2005
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    Bacalar, Mexico
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    Default Re: porch bracket - structural

    The pinned mortise along with the structure of the roof bolted to the house will be just fine unless there is a hurricane force wind or lots of snow.
    Jimmy
    __________
    Loving Living on Lake Bacalar.

  10. #10
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    Default Re: porch bracket - structural

    Quote Originally Posted by Jim Ledger View Post
    What are they supporting?
    Until the deck rotted away they supported a walkout 4x8 foot porch.

  11. #11
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    Default Re: porch bracket - structural

    still working on this. If we can document it enough that the town building inspector gives it a green light then I trust it will work.

    Will post pics as it progresses

  12. #12
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    Default Re: porch bracket - structural

    I've done several load-bearing versions of this. The first, many years ago, was completely spec'd by the architect. I don't recall all the details. It was a public building, though, and I'm sure I'd have heard of any failure.The second was very similar to your first image. I engineered myself. It had approx. 8' rise and 7' projection. It was epoxied floating tenons tenon at all three joints. The upper inside joint - which would possibly bear some tension load - was reinforced with thru-bolted steel straps. It supported a gabled roof structure and pediment which protected an entry door. It was lagged into a masonry building. It's held up for years.
    David G
    Harbor Woodworks
    http://www.harborwoodworking.com/boat.html

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

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