Squaring a Slab or building


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Old 09-16-05, 01:44 PM
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Squaring a Slab or building

Can someone please describe to me in layman terms how I square a slab or a building foundation by using the 3-4-5 triangular method. I am having a hard time understanding it. Thanks in advance for your help.
 
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Old 09-16-05, 04:09 PM
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Hope this helps

A 3,4,5 triangle is a triangle with sides of lengths 3, 4, and 5. The units (ft, inches, etc) do not matter, and the sides can be any multiple of these numbers (for example 6,8,10 or 15,20,25). The longest side will be the diagonal, the shorter two sides will be perpindicular (square).

To square a foundation using this, pick the largest easy multiple of 3,4 that will fit in your space. For example if you have a 7'x10' rectangular foundation, you would probably want to use 6',8'. Measure 6' from the very corner of the foundation where you want the square corner along the short side, and make a mark on your layout string or board. Then measure 8' from the same corner used before, but in the other (longer) direction of your foundation, and make another mark. Now stretch your tape between the two marks you just made. If you have a square foundation, this measurement will be exactly 10', or whatever your longest number was when you multiplied the 3,4,5. If it is not, you need to adjust the angle of one of the sides, rotating it from the corner you made your marks from.

Hope this helps, it is not as hard as it sounds once you do it a few times.
 
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Old 09-16-05, 07:56 PM
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PopPop,

It's a 3-4-5, and multiples thereof. Use the largest units that you can with that ratio.

From the corner that you want to be square, measure out 3 "units" in one direction, and 4 "units" in the other and mark those points. When you measure 'point-to-point', you'll have 5 units when the corner is square. It doesn't matter what the "units" are, as long as you use the same on all 3 sides. Could be 3", 3', 3 miles, or something like 90". You "4" side would be 4", 4', 4 miles, or 120" respectively. Then your long side ("5") would be 5 inches, 5 feet, 5 miles, or 150".
 
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Old 09-17-05, 04:51 PM
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Scary thing is, Lefty carries a 5mile long string on his truck..

 
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Old 09-18-05, 03:27 PM
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Actually, I carry 2, just in case one breaks!!

Seriously, the larger the "units" you use, the more accurate you will be.
 
 

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