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How to Square A Metal Roof - The 3, 4, 5 Triangle Method
Paul Rubio

By: Paul Rubio on December 7th, 2020

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How to Square A Metal Roof - The 3, 4, 5 Triangle Method

Metal Roof Installation | roof



How To Square A Metal Roof
If you’ve never installed a metal roof, then you may be surprised to learn that not all roofs are square. Squaring a roof is a critical installation step that needs to be completed after the roofing underlayment and eave trim have been installed. You must square your metal roof panels prior to installing the first sheet. Otherwise, the metal panels will drift off at an undesirable angle.

Fortunately, there’s an easy way to do this. The 3, 4, 5 triangle method will allow you to quickly snap a true squared reference line on your metal roof. This will ensure that all of your metal roofing panels are installed straight.

At Western States Metal Roofing, we manufacture the metal roofing, but don’t install the metal panels. However, we know that you still need help with the installation of your metal panels. We’ve been selling metal roofing panels manufacturer direct to homeowners and contractors for over 25 years. Our goal is to make your metal roofing installation as simple and hassle free as possible.

In order to make your roofing installation as painless as possible we’ve created step by step written instructions and pictures that illustrate each step. We’ve even made you an instructional video.

This article is intended to support the video. Follow the instructions within the video and refer back to this article if you need a written copy of the instruction.

What Is A True Square Reference Line On A Metal Roof

A true square reference line will serve as a guide to make sure your panels are going on straight. Once you begin laying down your panels, chances are that your panels will begin drifting off in an undesirable direction. Therefore, an important first step is to chalk a true square reference line onto the roof.

The best way to do this is based on a true 90 degree right angled triangle. This is any triangle whose sides are in the ratio 3:4:5, meaning 3 over, 4 up, and 5 across. This will give you a true right triangle.


What Is A 3, 4, 5 Triangle?

The 3, 4 ,5 triangle is based upon the Pythagorean Theorem. It's a true right angle triangle that starts out with measurements of 3 out, 4 up, and 5 across. Hence, the name of 3 4 5 triangle.

For larger roofs, the math is simple. Just use any multiple of 3, 4 and 5 to get your answer. For example, doubling the size of your roof would brings you values of 6 over, 8 up, and 10 across. Quadrupling it would be 12, 16, 20.


How To Square A Metal Roof

In this example we will be using the 12, 16, 20 triangle. You can do any triangle in multiples of three.

  1. Start at the lower eave corners of your roof. Set a base point of at least twelve inches from the eave and gable ends. This will be your starting point. This will be referred to as Mark “1”
  2. From Mark “1”, measure twelve feet across the eave of your roof
  3. Make a mark at the intersection of the distance from the first mark and sixteen feet from the eave of the roof. This will ensure the line is parallel to the eave. This will be referred to as Mark “2”.
  4. Going back to the mark “1”, measure upwards sixteen feet.
  5. From Mark “2” at the eave measure towards Mark “3” by twenty feet. Where these two measurements intersect will be the final mark.
  6. Snap a chalk line from the first mark to the final mark. This line will be the true perpendicular line to your eave.


how to square a metal roof

This will be referred to as Mark “3”


how to square a metal roof

During the installation you should constantly reference this line to ensure your metal roofing panels are being installed straight. We recommend creating an additional guideline every 8-10 feet from your reference line.

To do this, simply measure the perimeter length across from top and bottom and snap a line between the two marks.

Looking for more metal roofing installation videos, go to our YouTube Channel and subscribe as we post new installation videos weekly.

Click here to watch metal roofing videos on our YouTube channel!


Buy Manufacturer Direct And Save

Looking to save some cash on your metal roofing project? Western States Metal Roofing is a manufacturer that sells direct to homeowners and contractors. This can help you to save money on all of the metal roofing materials you’ll need for your house.

Go to the Western States Metal Roofing website to see our products and request a quote or a metal color sample as there are hundreds of colors to choose from.


Get a Free Quote for Metal Roof or Metal Wall Panels Today! Click Here

About Paul Rubio

Paul Rubio is the Vice President and one of the owners of Western States Metal Roofing. He has been in the metal roofing industry for 25 years. WSMR is a manufacturer of metal roofing, wall panels, and metal siding. We have colors and finishes that nobody else has with nearly 100 different colors in stock. Our selection of color options and finishes is likely the largest in the industry.