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Thread: Squaring up structures / planning layout ... shortcut?

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    I&C Engineer (mostly WWTP) Lakee911's Avatar
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    Default Squaring up structures / planning layout ... shortcut?

    Hi All,

    Suppose I'm building a simple rectangular structure and I lay out everything with string to establish the sides and elevation. Paralleling the strings is easy, but to square it up, I'd measure the diagonals, right? Well, is there an easier way than to shift, check, shift, check, shift, check to make them equal and thus square?

    So, given a parallelogram with sides equal to X and Y, diagonals equal to D and E and unknown angles, is there a formula I can plug this in to such that I get answer that tells me how much to shift one side such that I get a rectangle with sides equal to X and Y, diagonals equal to D equal to E and 90 degree angles?

    I have strings setup, but even with a helper, I think it's going to be tough to accurately measure the diagonals over and over again. Maybe set up extra batter boards to stretch a tape across?

    Thanks,
    Jason

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    Retired Defense Industry Engineer jadnashua's Avatar
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    One of the easier ways to create a 90-degree angle is with a triangle whose sides are in the ratio of 3:4:5. It will create a perfect 90-degree angle. You could make it out of anything, 2x4's cardboard, whatever. The longer you make them, the easier it would be to compare to your existing lines. 6'x8'x10' or anything with the 3:4:5 ratio will work.

    If you are going to do this a lot, you can buy lasers that create beams 90-degrees.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    I&C Engineer (mostly WWTP) Lakee911's Avatar
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    I've never been a big fan of that method ... it's tough to measure the diagonal (hypotenuse) on the edge of a string. If I'm building something and I can hook my tape to something it's much easier.

    I started to try to solve my original problem and it's tough because there are a lot of angles and not to mention that when I shift one side of the parallelogram, it will no longer have the same dimensions...

    Who said garages have to be square?

    Thx
    Jason

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    Moderator & Master Plumber hj's Avatar
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    Default square

    Measure one side and square the dimension, then do the same to the other side. Add the two together, and then take the square root of that number. It will be the EXACT dimension for the diagonal, but in the real world, it may only get you close to square, if your original measurements are off, or the form is not a perfect paralleogram. Therefore, after you adjust the form to that diagonal dimension, you will still want to check the other diagonal and make any slight adjustments.

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    Plumber jimbo's Avatar
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    Seems like you are trying to out-think this. Watch a good framing crew in action. They can measure the diagonals, and based on how much the differ, they know which side to smack with the sledge and whether to smack it once or twice. Usually two iterations max and they are done. They will have the wall up before you get your calculator out of the case.

    Small houses and great buildings are done like this every day.

    When you get to skyscrapers, they do use optical measuring equipment, since the tape measure gets funky over 50' or so.

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    Forum Admin, Expert Plumber Terry's Avatar
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    I use the 5, 4, 3 method.
    It's been working pretty good for me.

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    I&C Engineer (mostly WWTP) Lakee911's Avatar
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    Quote Originally Posted by jimbo View Post
    Seems like you are trying to out-think this. Watch a good framing crew in action. They can measure the diagonals, and based on how much the differ, they know which side to smack with the sledge and whether to smack it once or twice. Usually two iterations max and they are done. They will have the wall up before you get your calculator out of the case.

    Small houses and great buildings are done like this every day.

    When you get to skyscrapers, they do use optical measuring equipment, since the tape measure gets funky over 50' or so.
    That's what I need ... optical measurement! It'll be perfect, but then my wall will be out of plumb on one end so when I get up top it'll be caddywompus again. heh.

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