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Knowledge Center / How to Take a Roof Pitch

For new technicians, measuring a roof pitch can be a little daunting.  A slight miscalculation in pitch can make a huge difference when working on a roof. For example when placing a stand that is 4' long, a ¼” mistake in your pitch means a 1” mistake on the roof.  If you take your time however, you’ll find that taking a roof pitch is a snap.  The best way to determine roof pitch is as follows:

You will need:

  • 1 Level
  • 1 measuring tape
  1. Place one end of your level on the roof deck as close as possible to the install location.
  2. Position the level so that the bubble reads level. 
  3. At the end of the level on the down slope side, measure straight down from the bottom of the level to the roof deck.
  4. Divide that measurement by the length of the level.  In the illustration below, we have a 1’ level and 4” from the bottom of the level to the roof.  This means we have a 4/12 roof pitch.  In other words for every 12” out, the roof drops 4 inches.  When using a longer level, divide the measurement to the roof deck by the length of the level.   For example, let’s say that in the diagram below we had used a 4’ level and the measurement to the roof deck is 16”.  16 divided by 4 equals 4.  Again, we have a 4/12 pitch.   

 Tips:

  • Try to use a longer level for truer measurements.
  • Take pitch readings from several spots to make sure you get the same readings. 
  • Newer homes use factory built trusses and, as such, tend to be more precise (i.e. 4/12, 5/12, etc.).  Older homes had rafters, built on site.  Though not as common, it is not entirely unusual for older homes to have odd pitches such as, say 3 ½ on 12. 
     

 

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