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Discussion Forum

squaring techniques

Dan019 | Posted in General Discussion on January 24, 2006 03:49am

Had to lay out for postholes by myself. Had a heck of a time getting it square. I know all about Pythagoras Theorem (Asquared + Bsquared = Csqaured) but my arms have a tough time stretching out to 5’ and 9’. So I was wondering what tricks others have used to square something up when there is no help available.

I was thinking about using 3 pieces of thin wall conduit bolted together at the ends (cut to the proper lengths of coarse). This would at least be easy to break down and store in the van.

Anyone have any good proven techniques, short of buying a $300 laser?

Dan019

 

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  1. Stilletto | Jan 24, 2006 03:55am | #1

    Built a 16' by 24' hunting cabin this summer found myself in the same situation so I built my box 16x24 in the buildings location measured by pulling corner to corner and marked my holes and augered them out worked for me it might for you.

    1. Dan019 | Jan 24, 2006 04:36am | #3

      Good idea.I thought of that... after I was finished, thinking there's got to be an easy solution.Dan 

  2. DanH | Jan 24, 2006 04:31am | #2

    Just get a piece of light rope or heavy cord, tie it in a 12-foot loop, and mark out 3, 4, and (the remaining) 5 foot lengths. Put one stake (a thin metal rod is best) in a known corner, the next stake out along the line at the 3 foot mark (between the two), and the other stake along the other line at the 4 foot mark (between 1st and 3rd). If you have all three stakes at the marked points and all parts of the rope are taut, you have the angle.

    If you want more accuracy just double/triple/quadruple the rope and the marks between. You can also make the two arms of the right angle equal length if you want. Just make the third part of the rope 1.414 times one of the equal arms.

    If you have a calculator, you can mark out the two supposed arms of the right angle, measure them, and do the squaw on the hippopotamus thing.

    If ignorance is bliss why aren't more people

    happy?

  3. ponytl | Jan 24, 2006 07:16am | #4

    i watched some mexicans set forms, pour a slab...  build an aprox 1200sf house and have nothing and i mean nothing (no tape measure, no level, no lazer)

    they had a water hose (water level) and a string (chalk line) and they cut a 4x8 sheet of plywood on site... they cut it first in half then corner to corner ie: 2 - 4ft sq's then cut the other half of the sheet in half again.. one half of this they cut corner to corner ie:  a 2x4 ft sq then the other 1/8 sheet they made 4  2'x2' sq's (cut corner to corner) to 2 of these they nailed a 1x2 "edge" and used these  as "speed sq's" the house was framed & closed in in 1 day... roofed & bricked in 3days... 

    if you have been doing so much with so little for so long... u can pretty much do anything with nothing

    p

  4. Pete | Jan 24, 2006 07:41am | #5

    once you layout two holes you can split the difference between them.  pull the other length you need from that point and triangulate back to the first two holes to find the center relative to them.  then it's a walk in the park.

  5. dustinf | Jan 24, 2006 07:47am | #6

    Just get a piece of light rope or heavy cord, tie it in a 12-foot loop, and mark out 3, 4, and (the remaining) 5 foot lengths. Put one stake (a thin metal rod is best) in a known corner, the next stake out along the line at the 3 foot mark (between the two), and the other stake along the other line at the 4 foot mark (between 1st and 3rd). If you have all three stakes at the marked points and all parts of the rope are taut, you have the angle.

    Ditto on what DanH said.

    --------------------------

    It's only satisfying if you eat it.



    Edited 1/23/2006 11:50 pm ET by dustinf

  6. User avater
    JeffBuck | Jan 24, 2006 08:37am | #7

    "but my arms have a tough time stretching out to 5’ and 9’."

     

    Uh ... use a tape measure instead?

     

    or two ... three even ... or a coupla simple nails at the corners .... or a rock ... or a twig ... or a screw driver ... or a ... and a  ... or a ....

    Jeff

        Buck Construction

     Artistry In Carpentry

         Pittsburgh Pa

  7. User avater
    hammer1 | Jan 24, 2006 04:41pm | #8

    It's pretty easy. You need two tapes, a pair of 100' reel type tapes with the D loop end will do most residential jobs. You also need something to hold the end of the tape, 20d spike, welding rod, marker flag, etc. Do your Pythagorean calculations for the over all building size to get the hypotenuse. A 10' x 12' building has a hypotenuse of 16.970', for example. Place a spike through the end of the tape loop and stick it where one corner will be. Measure out the overall length and spike the other tape on that corner. Now pull the two tapes so that the hypotenuse and the width of the building meet on the two tapes and place a stake/mark. Now reverse the pull on the two tapes, while they are still on the same corners, so that the hypotenuse measure becomes the width and the width becomes the hypotenuse. Again, where the two meet, place a stake/mark. Double check that the two stakes you set are the same distance apart as the length. They should be right on if your math was done correctly. You can, actually, do this from any known corners, not just the length first. For larger or layouts that bump in and out, you just break them into their rectangular sections. The 3-4-5 method of measuring corners for squareness isn't very accurate unless you are extremely accurate. Knowing exactly how far each corner measures on the hypotenuse takes the 'trial and error' out of the picture.

    Beat it to fit / Paint it to match

    1. User avater
      SamT | Jan 24, 2006 06:33pm | #9

      Hammer,

      Do your Pythagorean calculations for the over all building size to get the hypotenuse

      The 3-4-5 method of measuring corners for squareness isn't very accurate

      They're the exact same process. They have the exact same degree of error. The longer the hypotenuse the more accurate. For both methods.

      If you pull a 60'x80'x100' 3-4-5 on a 24'x44' footprint, the 3-4-5 method is more than twice as accurate than measuring the actual hypotenuse. BTW, how many 1/32"s is 0.11985634456667"? Do ya think there might be an error in converting that or trying to read 3.745/32", (~21/128")?

      In my considered opinion, both methods are good enough for all but the most exacting fabrication work, possibly, done for NASA.

      SamT

      1. DanH | Jan 24, 2006 06:55pm | #10

        The other way is to make the two diagonals match. It is necessary to first make sure you have a true parallelogram, though -- opposite sides equal.
        If ignorance is bliss why aren't more people

        happy?

    2. r | Jan 24, 2006 10:01pm | #18

      Pythagoras just called me - says he's unhappy with the hypotenuse of your 10' X 12' building (insert little smiley face here).

      1. User avater
        hammer1 | Jan 25, 2006 01:46am | #19

        Thanks, r. It's 10' x 12' not 12' x 12', right? Not much sunlight on the old solar calculator last night. Good thing I didn't pour the concrete! I'd be scratching my head trying to figure out why the stakes weren't the same measurement apart.Beat it to fit / Paint it to match

        1. brownbagg | Jan 25, 2006 02:01am | #20

          batter boards.. 2+3=7

          1. kicker | Jan 25, 2006 10:01am | #21

            Why not use pyth. or the 3-4-5 method, and check with equal diagonals? If you have build a rectangle (with matching length sides), and have it square, they will both match.

            Sometimes a quick second check will catch a problem before it starts.

          2. JoeBartok | Jan 25, 2006 09:06pm | #22

            Dan, check out this Right Angles pdf.Joe Bartok

            File format
          3. JohnSprung | Jan 25, 2006 10:41pm | #23

            One thing to add to that PDF:

            Start with a straight line.  Draw two circles, one centered at each end of the line, having their radius equal to the line.  The circles will intersect in two points.  Draw a new line between those points, and it'll be perpendicular to the original line.

            That's fine for geometrical theory.  For construction, you don't need to make the whole circle, just short arcs where it intersects the other circle.  In many cases, one of those intersection points will be on the neighbor's property or inside an existing building.  So you can measure and divide by two to use the midpoint of the first line instead.   

             

            -- J.S.

             

          4. JoeBartok | Jan 25, 2006 11:13pm | #24

            Thanks John. Good point, some information on geometric methods of finding perpendiculars and squares would be a good addition to that document.

            Come to think of it here's another thing I should include: inscribing an angle in a semi-circle always creates a right angle. I've never actually used this in the field ... but who knows? It might just come in handy someday.

             

             Joe Bartok

  8. csnow | Jan 24, 2006 08:11pm | #11

     

    They sell a big folding square for this sort of problem.

    If you made your own, I would think it would be better to use some sort of flat stock.

    View Image

    http://tinyurl.com/bx58j

    1. rody | Jan 24, 2006 08:40pm | #12

      Not an expert or even a pro, just a part time farmer. We have always had the best luck with measuring the diagonals and getting them equal. Lately we have used string and batter boards to set the locations. Its much easier to slide the strings around to get the dimensions right and use the string for the outside corners of the posts. Be sure to measure to the corner of the strings for the diagonal, not the edge of a round post. Don't ask.

      We have built several pole buildings, the last was 48'X138'. The diagonals were within 1/2" tolerance at ground level and at the 12' top of the 6X6 posts. Take your time and remeasure as many times as needed then measure 4 more times. It is worth it in the end. Just some advice from a veteran of some good pole buildings and some pretty ugly ones too. <g>

       Lefty - Lurker without an attitude or a clue

      1. dustinf | Jan 24, 2006 08:49pm | #14

        You have to be careful measuring diagonals.  If the two side dimensions aren't exactly the same length, you will end up with a parallelogram.--------------------------

        It's only satisfying if you eat it.

        1. DanH | Jan 24, 2006 08:58pm | #15

          Actually not. You end up with a total mess, more likely to have two sides angling in towards each other. If all the side dimensions are equal then that's when you have a parallelogram.
          If ignorance is bliss why aren't more people

          happy?

          1. User avater
            Sailfish | Jan 24, 2006 09:31pm | #16

            Imagine all those kids who said

             

            "I ain't never gonna use no geo metry in real life when i git outta skool!"-----------------------------------------------------------------------------

             

            WWPD

          2. rody | Jan 24, 2006 09:33pm | #17

            Yes, all 4 sides have to be dead on AND the diagonals have to be equal or you get some mud ugly results. The batter boards help and give you room to slide things around to get all 6 dimensions dead on. I'll defer to the experts on all technical issues. I'll stick to the dumb end of a post hole digger and a steel tamper <g>.

             Lefty - Lurker without an attitude or a clue

  9. mike4244 | Jan 24, 2006 08:44pm | #13

    Assume a building 20'x30'-0".Set a hub at each end of one 20'-0" wall,exactly 20'-0" apart. Pull a tape from one nail about 35'-0 ,scribe an arc in the dirt.Repeat with the other side. Where the arcs cross, drive a hub.Now do the same thing and mark the intersection, this is 10'-0 from each wall,the centerline of the building in one direction.Measure 30'-0 from the first hubs, put hub in where 30' and 10'-0 intersect.

    Now measure exact 30' and 20' and mark the hub,put a nail there and pull 20'-0" to the last hub. When done, check your diagonals. If you did this on fairly level ground you will be dead square.

    mike

     

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