How to Calculate the Slope of Your Roof

August 14, 2015

At Accord Construction, we want to make the process of repairing or replacing your roof as easy for you as possible.  Knowing the pitch of your roof is useful when designing an addition, installing skylights, or cutting new rake boards. The slope of a roof affects how roof systems are installed and which type of materials can be applied on top of the roof. Roof slope can also determine the effectiveness of water drainage in your home. If there is a problem with water collection on the roof, it is quite possibly related to roof slope. Because of this, understanding how to measure the slope of a roof can be critical for a homeowner. We have created this article to help you calculate the slope of your roof. Call us at (405) 302-5520 to learn more or to arrange a roof inspection.

How to Determine Your Roof Slope

Your roof slope is calculated by the number of inches it rises for every 12 inches it extends horizontally. So a roof that rises 6 inches for every 12 inches of horizontal run has a 6-in-12 pitch. Slope can also be expressed as a percentage. So a roof that rises 1 inch in 12 horizontal inches has a slope of 8.33% otherwise known as 1/12.

If you want to determine your roof slope without going outside or on top of your roof, you can go to your attic. Measure 12 inches from one end of the level and make a mark. Place the end of the level, in the attic, against the bottom of a roof rafter. That measurement is the number of inches your roof rises in 12 inches!

If you plan on determining the roof slope by going on the roof, you will need to place a level across the top ridge with a 12 inch mark that rests right above the center of the ridge. Make sure it’s level and take measurements from the surface of the roof to the bottom of the level. The inches that you get as a reading is your roof pitch. When your tape says 6 inches, then that means the roof pitch/slope is 6/12 (or 50%). If there are other roof layers underneath your surface roof, then you’ll have to determine the pitch in another way. You’ll have to consider the thickness of the layers underneath that protrude above the roof encasing. Add the amount from the thick roof layers to the tape measurement reading. If the roof that protrudes above the roof is 2 inches then add 2 inches to your tape reading. That is, if your tape reading read 8 inches then add 2 inches, giving you a total 10/12. If you need to calculate the area of the roof after this, multiply the square footage with the roof pitch factor and you’ll get the total area of the roof.

Types of Pitched Roofs


Now if you are considering building or remodeling your home to include a pitched roof, you should know about the different types. There are low pitched roofs, medium pitched, and steep pitched. These types are decided by the slope of a roof. The low pitched roofs have slopes below 3 ½ and are easy to build. However, certain types of materials such as asphalt shingles shouldn’t be used for these types of roofs – special roofing materials are needed for roofs with slopes this low.

The medium pitched roofs are in between 3 ½ and 7 ½ and are the most commonly found roofs in the United States because it allows storage space for an attic. This type of roof is also found above sheds and garages.

Steep pitched roofs are ones that go beyond the 7 ½ range. If your roof is of that pitch, you’ll need special gear and equipment in order to walk or work on your roof. These roofs are typically more expensive but will last longer than the other types of roofs.

Accord Construction is available to help you through the roofing process. If you have questions regarding how to calculate roof pitch/slope or about the different types of roof pitches, you can always call our office. We can walk you through the process of calculating it or we can measure the roof pitch if you’d rather not. Accord Construction is fully licensed and certified. Not only that, but we are up to date with all of the latest roofing techniques to make your home safe and dry. We’re the best choice for professional roofing in Oklahoma City. No matter what your needs are, we’re here to help you achieve your dream roof.
Call us at (405) 302-5520 to arrange a consultation.

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