How to Find Square Layout with a Plumb Laser Level

A crucial part of every layout task is marking square, 90-degree corners for exterior foundations or indoor walls. For very small areas, a contractor’s square may do the trick, but laying out 90-degrees over a larger area requires a bit more precision. Most contractors learn the 3-4-5 or Pythagorean method to mark square.

Laying Out Square Using the Pythagorean Method

The Pythagorean method steps are as follows:

1. Measure 3’ out from a point in one direction.
2. Measure 4’ out from the same point around 90° in the other direction.
3. Measure across the two points and adjust the angle until the distance on the third side of the triangle is 5’.
4. You can also use multiples of 3-4-5 in the same ratio (such as 6, 8, 10) to form larger or smaller right angles

The method typically requires at least two people and is less precise. If the angle is off be a few degrees, the error is only compounded as you extend your level line further. Bottom line, the method is not as precise, takes longer, and is hard to do alone.

Using the PLS 5 Dot Laser to Layout Square

The PLS-60545 HVD 500 laser point detector is designed to attach to the pendulum layout target and comes with the PLS 5 System configuration for use at long distances, outdoors, or in bright light conditions.

The PLS 5 features a left, right, top, and bottom dot aligned at 90 degrees to a forward-facing dot. You can quickly mark square from any baseline following the procedure below:

• 1. Place the PLS 5 on the floor (use the PLS-20844 floor stand if necessary) and align the down dot to the pivot point.
  2. Align the forward-facing dot to align to your baseline, whether it be a survey marker on a new foundation or the common edge of the primary wall or foundation edge.
  3. Using the PLS-10090 Pendulum Layout Target, find the 90-degree side point from the PLS 5 and easily transfer the mark to the floor. Do this at varying lengths and you can then snap a chalk line or use a contractor level to draw a straight edge along the line.
  4. When being used outdoors, bright lighting conditions, or longer distances, the PLS-60545 HVD 500 laser point detector is designed to attach to the pendulum layout target and comes with the PLS 5 System configuration.

This method can be done with a single person in a fraction of the time as the 3-4-5 method. Bottom line, using a laser level equals more precision in less time, and it can easily be done by one worker. The PLS 5 is accurate to 1/8” at 50’ meaning it’s a valuable tool when you need to mark square over a longer distance. For even great accuracy over longer distances, you can also use a PLS HVR 505 rotary vertically to give you 1/8” accuracy at 100’.