How to Find Square on a Foundation

Determining the square of the foundation is important to get the proper right angles in the corners of a room. In construction-speak, it is called the 3-4-5 rule, but for mathematicians it is known as the Pythagorean Theorem. This theorem states that "A" squared plus "B" squared equals "C" squared. This formula determines if your foundation is properly squared. In other words, if you have the proper squaring corners. No room is perfectly square; however, getting the corners as close to 90 degrees as possible is important.

Things You'll Need

• Tape measure

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Instructions

1. • 1

     Use a tape measure to measure the length of the foundation. Find the square of the number. If the length is 3 feet then the square is 9.

   • 2

     Use a tape measure to measure the width of the foundation. Find the square of the number. If the width is 4 feet then the square is 16.

   • 3

     Add the squared numbers together: 9 + 16 = 25

   • 4

     Calculate the square root of the answer: square root of 25 is 5. The diagonal length of a 3-by-4-foot room is 5 feet. Use a tape measure to verify the diagonal distance is 5 feet.