How do you set out using 345 method?

Asked by: Ms. Mara Zulauf Jr.  |  Last update: February 10, 2026
Score: 4.1/5 (17 votes)

The 3-4-5 method sets out a perfect 90-degree (square) corner using the Pythagorean theorem, where you measure 3 units along one line from the corner, 4 units along the perpendicular line, and the distance between those two marks must be exactly 5 units (e.g., 3 feet, 4 feet, and 5 feet) for the corner to be square. You can scale this up for larger projects (e.g., 6-8-10 or 9-12-15) for greater accuracy, often used in construction for foundations or framing.

What is the 345 method of setting out?

The 3-4-5 method is commonly illustrated by creating a triangle shape. One side is measured at three feet (the straight line), the second at four feet (the perpendicular line) and the last at five feet (across) – hence the aptly named '3-4-5 method. '

What are the steps of setting out?

The key steps in setting out include initial site planning, transferring design coordinates, establishing control points and markers, verifying alignment, and continuous monitoring throughout construction to ensure accuracy.

How to draw a setting out plan?

The centre line method of setting out is generally preferred and adopted. 1. From the plan, the centre line of the walls are calculated. Then the centre lines of the rooms are set out by setting perpendiculars in the ratio 3:4:5.

What are the tools for setting out?

Tools Used for Setting Out Measuring: Steel tapes, measuring wheels Angles: Theodolite, total station, builder's square Leveling: Spirit level, laser level, dumpy level Marking: Chalk lines, pegs, spray paint Common Challenges in Nigeria (NG) Unstable soil may shift reference points.

345 rule, trade secret, everybody should know this trick

16 related questions found

How to set out square for a large building?

Put the measuring tape at the corner where the two walls meet, and measure four feet (121.92 centimeters) along the width of the area. Mark the place on the floor with a chalk mark. Measure a straight line (i.e. the hypotenuse) between the two chalk marks.

Is a 3/4/5 triangle always 30-60-90?

What are the angles of a 3-4-5 triangle? The angles in a 3-4-5 triangle are always the same. The 3-4-5 triangle is a right triangle which means one of the angles is 90 degrees. The other two angles are 36.87 and 53.13 degrees.

What is the 6 8 10 rule?

The 6-8-10 rule is a practical application of the Pythagorean theorem (a2+b2=c2a squared plus b squared equals c squared𝑎2+𝑏2=𝑐2) used in construction and DIY projects to create a perfect 90-degree (square) corner, especially when laying out foundations, decks, or walls, by measuring 6 units along one side, 8 units along the other, and ensuring the diagonal (hypotenuse) between those points measures exactly 10 units. It's a scaled version of the more basic 3-4-5 rule, allowing for larger measurements while guaranteeing a square corner. 

How could you use the 3/4/5 method to set out a foundation?

From one reference corner, measure 3 units at a right angle direction. From the same point, measure 4 units along the baseline. Adjust until the diagonal distance becomes exactly 5 units. This confirms a perfect 90° angle for accurate foundation setting.

How to make sure your frame is square?

Measure Corner to Corner

  1. Choose any corner of your deck frame as your starting point.
  2. Measure diagonally to the opposite corner of your deck frame.
  3. Repeat the measurement from a different starting corner to its opposite corner.
  4. If both diagonal measurements are equal, your deck frame is square.

What is the easy trick to find squares?

To square any number:

  • Subtract the last digit of the number being squared.
  • Add the last digit to the number being squared.
  • Multiply the numbers from Step 1 and Step 2.
  • Square the last digit of the number being squared and add it to the answer from Step 3.

What is the 45 45 90 rule?

The 45-45-90 rule describes the fixed side-length ratio in a special type of right triangle: an isosceles right triangle with angles 45°, 45°, and 90°. If the equal legs have length x, the hypotenuse is always x√2, giving a side ratio of x : x : x√2, or simply 1 : 1 : √2 for legs : hypotenuse. This rule allows you to find any side if you know one, by multiplying the leg by √2 to get the hypotenuse, or dividing the hypotenuse by √2 to find the legs.
 

How to use 345 triangle?

3-4-5 Rule Layman's Terms:

If the short side of the triangle is 3 feet, and the leg that extends from it 90 degrees is 4 feet, the hypotenuse, or longest leg, will be 5 feet. This technique simply requires that the carpenter create a triangle in the corner of the lines that are to be square (90 degrees) to each other.

Does 5 12 13 make a right triangle?

Yes, 5 12 and 13 make a right triangle. They are referred to as Pythagorean triplets, where 5 squared and 12 squared equal 13 squared, which is the application of the Pythagorean theorem.

What is the builder's square method of setting out?

The Builders square is used for setting out right angles. When made, its accuracy could be guaranteed, out over time when exposed to site conditions its accuracy should be questioned. It is constructed of 75mm x 30mm timber, half jointed at the 90° angle with a diagonal cross brace tendon into its side length.

Is the 345 method foolproof?

The 3-4-5 rule is a handy and foolproof way to determine if a corner is perfectly square when doing carpentry or other DIY projects, from building a deck to laying tile. And if your corners aren't square when laying a foundation or building a frame for a deck, your later measurements will be off, too.

Which methods is the most accurate for squaring a building layout?

The 3-4-5 Method is an accurate method used in getting the exact square of a plan! To get a perfectly square corner, you want to aim for a measurement ratio of 3:4:5. In other words, you want a three-foot length on your straight line, a four-foot length on your perpendicular line, and a five-foot length across.

How to do setting out of a building step by step?

10 Steps of Setting Out A Building :

  1. 2) Prepare the necessary equipment before commencing. ...
  2. 3) Establish a datum peg where it will not be disturbed. ...
  3. 4) Establish frontage line. ...
  4. 8） Repeat step 7 for remaining profiles. ...
  5.  Take a string line and attach it to one of the survey peg. ...
  6. 10) Remove the corner pegs and start excavation.

What are the 10 instruments used in surveying?

Types of Surveying Instruments

  • Total Station. ...
  • Auto Level/Dumpy Level. ...
  • Theodolite. ...
  • GPS (Global Positioning System) ...
  • Photogrammetry/Drone. ...
  • Optical Square. ...
  • Plumb Bob Laser. ...
  • LDM (Laser Distance Meter)

How to do a set out?

Setting out involves working out the location and extent of the building on site. Each site is different, so start by establishing the particular conditions. Use information from territorial authorities' records combined with an on-site inspection. carpentry or foundations licence.