Building a bridge

Discussion in 'Homesteading Questions' started by Joe in MO, Apr 26, 2005.

  1. Joe in MO

    Joe in MO Active Member

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    Here's another question...I'm wanting to build a bridge over our creek in the back. It will be approx. 4 ft. wide x 18ft long. It will be mostly a "people" bridge although I'll proably drive a riding lawn mower over it.
    My problem is trying to know what size lumber to use. I thought of using 6x6x18 but I talked to a lumber man and he said that by using two 2x12x18 and bolting them together will be stronger than using the 6x6's.
    Does anyone know if this is true or not? Or is there a better way? I'm planning on using either size to go from one end of the creek bank to the other and then use 2x6 as my planks.
    Thanks again for all the help,
    Joe
     
  2. fordson major

    fordson major construction and Garden b Supporter

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    i am planing a few crossings such as yours but am using truck/bus frames as the main beams to allow removal in the fall. figure the frame will hold up bettter than wood.
     

  3. dale

    dale Well-Known Member

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    Yes the 2x12x18 placed together would be stronger then just the 6x6x8 lumber.

    Its a engerineering thing... But I used to argue with my brother the buider.. I was on your side... I always lost.. the 2x12's nailed, bolted or however you are going to put them together will be structuerly (sp?) stronger.

    They even will tell you that on This Old House....

    dale
     
  4. GrannieD

    GrannieD Well-Known Member

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    This is an observation Joe, but I don't know your creek,our little creek gets up fast & furious when we get a couple rainy days..My neighbor put a bridge over his to drive to his house & it gets torn out every once in awhile...Be sure you check with folks aquainted with your area of the creek if you haven't been around it for years..It sure can be done,but might require some special engineering to be a lasting bridge...Good Luck.. We're in SW Mo. ... GrannieD
     
  5. Quint

    Quint Well-Known Member

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    Telephone poles were great for this kind of thing.
     
  6. foxtrapper

    foxtrapper Well-Known Member Supporter

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    How strong do you want it? With the timbers you're suggesting, you could drive an automobile on it.

    I've got a 16' creek crossing bridge doing the exact same purpose as yours will be. Two 2x8x16's, no central posts, just resting on the ends. Stand in the middle and jump up and down, it wiggles about three inches. 2x6's crosswise for decking, which is overkill and heavy. I should have just used one inch thick decking planks.

    If you can use posts to help support it at any length along the span, you'll make it steadier and stronger. I chose not to because my creek floods frequently, and debris simply gets caught on posts.
     
  7. Joe in MO

    Joe in MO Active Member

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    Thanks for all the help.
    Quint -- Yes, I wanted to use telephone poles. Even had some in the front yard, but could not move them to the back.

    Joe
     
  8. FolioMark

    FolioMark In Remembrance

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    Joe:

    Heres how to move those phone poles....First you buy a couple of cases of beer. Then you invite all your friends and their young sons of drinking age over for a party. After a couple of hours, you bet all the older men they cant move one of those poles as fast as the young ones. Build your bridge. :rolleyes: :haha:
     
  9. bethlaf

    bethlaf Homegrown Family

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    actually, the main thing here is where isthe creek ? does it source on your property?
    is it what is considered a "navigable waterway"in other words is it year round or seasonal , if its year around, and doesnt source on your land, or end on your land, but simply passes through , i think the law says that you cant build a non structurally certified bridge....
    jsut a thought, though it might be in an area where noone will know ...
    in which case if you build it, and hope the law doesnt come ...
    just musing outloud here

    im the first to admit i dont know the missouri laws when it coems to streams and such , but i do know back home ( Wis) my aunt bought a beautiful piece of land, 20 acres on a hill, noone building around for miles, to get to it , you had to cross a creek , about 3 foot wide and 5 inches deep
    when she went to build her house, she built a bridge across said creek, with stout concrete piers and all ,
    the state saw on an overfly the bridge, she was ordered to remove bridge because it was a quote "navigable waterway" and her bridge "Might" block public acess to said stream .....
    it was a long legal battle, in the end, she lost .. she now drives over the stream , shich for some reason has developed a nice pile of gravel right where she has to drive across, isnt nature amazing ......

    just my thoughts
    Beth
     
  10. Joe in MO

    Joe in MO Active Member

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    I'm thinking of saving some $$ and instead of using store bought lumber, cutting trees down instead. I have quite a few long straight trees that I can cut down and use that for the lumber to span across the creek.
    Is this a good idea or am I dreaming??
    Thank you,
    Joe
     
  11. desdawg

    desdawg Well-Known Member

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    Go for it. That's where telephone and power poles come from, maybe a different species but if in doubt throw in and extra one or two.
     
  12. stanb999

    stanb999 Well-Known Member

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    I would use the largest, cheapest, hardest logs I could find. In that order. But beware that softer woods like pine will rott out much sooner that a hard wood. The strength is different but of little consequence. Because if your like me you will over build it anyway. The other thing to remember is to build a good abutment. Keep the ends of the structural parts high and dry. If you use logs like you said you might consider paint or stain of some kind to prevent the insects from moving in. I always say build it once, Built it right, Make it last.
     
  13. Little Quacker in OR

    Little Quacker in OR Well-Known Member

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    :) Hi, I am no engineer....but I did put a little bridge about the size that you are contemplating across a creek here. Just a little creek and with help of course, we laid 4 X 8's X 20 ft long across for supports and the 2" x 8" planks(cedar)were screwed to this with decking screws. We made it 6 ft wide so I would have no trouble "finding" the bridge with the mower! LOL There's also planks on the sides for curbing.

    IT wasn't all that hard, just need some muscle to help with the long supports as they are heavy!

    i think you are all talking "overkill" here and I probably used stouter lumber than I really needed.

    LQ
     
  14. fordy

    fordy Well-Known Member

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    ..................IF , you decide to use 2x12's , cut strips of 3/4" , CD grade , exterior grade plywood and insert them between 3...2x12's x 20 feet long if that is the appropriate lenth and Glue...and Bolt\nail them together then treat with some brand of exterior preservour . I've seen lots of support breams in homes built in this fashion . You should really use treated yellow pine lumber no matter the Dimensions . fordy.. :)
     
  15. Don Armstrong

    Don Armstrong In Remembrance

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    As people have said, you're likely to have issues with what is legal in building a bridge, since abutments and foundations have the potential to block or dam the waterway, or interrupt water flow and trigger erosion. I'm not necessarily saying you should obey stupid rules or regulations, but it's always safer to know what laws you're breaking how than to do it in ignorance.

    That said, one effective bridge is a truck bed. Keep an eye out for tabletop trucks or trailers. If you can find one cheap, it will be strong enough. Some trailers are no longer long enough, so are sold cheap. Some trucks get burnt out, but the tabletop truckbed is still in fair condition. If you can build foundations each side of the creek, then rest your truck-bed on them, you've got a bridge. Just depends on finding one the right price then.

    Alternatively, put in culverts and build a road across them. Not really a bridge - just lumps of concrete the water flows through, with a road on top.
     
  16. Cyngbaeld

    Cyngbaeld In Remembrance Supporter

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    You can get a book on pole frame building at your local library that should have spans and loads for different sizes of lumber.