Understanding Pitch on a Roof

Pitch on a Steep House Roof

What is Pitch on a Roof

The pitch on a roof is really simple once you understand how to calculate it. After this article roof pitch is something you should never have a problem with.

A 1/12 pitch is very flat and a 12/12 pitch is very steep. To figure your roof pitch you simply calculate the amount of rising for every foot over. For instance, if in a one-foot span your roof goes up one inch your roof is a 1/12 pitch. On a 1/12 pitch for every foot across it goes up one inch.

On a 2/12 pitch, your roof will go up two inches for every foot over. For a 3/12 pitch, your roof will go up three inches for every foot over. Hopefully, I’ve explained this clearly. I’ll give a more detailed example.

For a 4/12 pitch roof, it should be four inches high at one foot in. If the total width of your house is twenty feet then it will be ten feet to the center of the house. When you measure you should have a rise of 40 inches. A 4/12 pitch is the most common. It is also very easy to walk.

Do you know how many degrees your roof is? We made it easy for you down below.

Chart

  • 1/12 pitch = 4.75 degrees
  • ———————————–
  • 2/12 pitch = 9.50 degrees
  • ————————————
  • 3/12 pitch = 14.00 degrees
  • ————————————
  • 4/12 pitch = 18.50 degrees
  • ————————————
  • 5/12 pitch = 22.50 degrees
  • ————————————
  • 6/12 pitch = 26.50 degrees
  • ————————————
  • 7/12 pitch = 30.25 degrees
  • ————————————
  • 8/12 pitch = 33.75 degrees
  • ————————————
  • 9/12 pitch = 37.00 degrees
  • ————————————
  • 10/12 pitch = 40.00 degrees
  • ————————————-
  • 11/12 pitch = 42.50 degrees
  • ————————————-
  • 12/12 pitch = 45.00 degrees
  • ————————————-
  • 13/12 pitch = 47.25 degrees
  • ————————————–
  • 14/12 pitch = 49.50 degrees
  • ————————————–
  • 15/12 pitch = 51.50 degrees
  • ————————————–
  • 16/12 pitch= 53.25 degrees
  • ————————————–
  • 17/12 pitch = 54.75 degrees
  • ————————————–
  • 18/12 pitch = 56.25 degrees
  • ————————————–
  • 19/12 pitch = 57.75 degrees
  • ————————————–
  • 20/12 pitch = 59.00 degrees
  • ————————————–

This chart may also be on your speed square depending on the brand.

Be sure and measure even with the bottom of the gable to the peak and not from the ground to the peak. Your lawn will not be level enough to get an accurate measurement.

To find your place to measure from on the gable you can stretch a string across the front of the house. Make sure your string is even with the bottom of your rafter on each end of the house.

Tool for Finding the Pitch

You can also buy a tool that will help you calculate the degrees or pitch of the roof. You can get it online, at Home Depot, or your local hardware store.

Another Way To Find The Roof Pitch.

Setting up a string can be a little annoying. If you don’t want to measure from the peak of the house to the string there’s an alternative. Get a level and a tape measure. Make a one-foot mark on your level and climb up to your roof. Hold your level with one end on the roof and pull the other end up till it’s level. Now check the measurement from the roof up to your level. That will give you your roof pitch.

Calculating Rafter or Metal Measurements

There are tools you can use to calculate the length of your rafter or your metal. However, it’s not a bad idea to learn how to do this on your own without anything more than a calculator.

Step One

First, we need to figure out what pitch your roof is. I won’t explain that again since I already talked about it above.

Now that you’ve calculated your pitch it’s time to calculate the rise. This is very easy, divide the with of the entire building and multiply it times the pitch. For example, your building is twenty feet wide and your roof is a 4/12 pitch. Divide twenty by two equals ten. Now multiply ten times four. You have forty inches of rising.

When you figure this measurement be sure and add on for the overhang. For example, if you have a foot overhang, your measurement to the center would be eleven feet.

Step Two

Now that you have your rise figured out you should convert it to feet instead of inches. Forty inches equals three feet four inches. Multiply this number times itself. Your number should come out to 11.108889. Don’t skip this step without converting to feet your end result wouldn’t be correct.

Step Three

After your done with the above measurement it’s time for the next step. Multiply the measurement of half the width of the building times itself. Remember we said that number is ten. Ten times ten equals one hundred.

Add your first measurement to your second measurement (100 + 11.108889 = 111.108889.) You should come out with (111.108889.)

Step Four

You’ve added these two numbers together now find the square root.  The square root of 111.108889 is 10.5408201294.

Answer

So your metal or rafter length for a twenty-foot building is a little over (10 feet 6 inches). 

Note we didn’t add overhang on this building. If your building has an overhang be sure and add that on to your measurement.

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