How To Correctly And Easily Measure A Roof Pitch

A diagram demonstrating how to measure a roof pitch accurately.

Why do you want to know your roof pitch?

There are a number of reasons you might want to find out how to work out the pitch of your home’s roof. For example, you might be installing a new addition, adding more square footage to the roof. In addition, Local zoning laws may require the new roof to meet certain angles, and depending upon which roof pitch you have, certain roof products may not be weather appropriate.

As a consequence, finding out how to determine your roof pitch in can be very important.

The old fashioned way

Traditional carpenters and died in the wool technophobes like to use the old fashioned way. This involves the use of three tools, a level, a metal t-square ( you can also use a tape measure) and perhaps a grease marker.

Most people, noting that it is infinitely safer (particularly in snowy, icy or rainy weather) like to measure in the attic of the house. You may need to move some insulation around but find a bare roof rafter. Then, using your level (an 18 or 24-inch level is best) first place the end of the level against the bottom of the rafter. Make sure it is level, as indicated by the bubble, then move 12 inches down the level and mark it with a grease pencil. (Many levels have inches clearly marked, so it’s not then necessary to use the grease pencil.)

Finally, from the 12-inch point, use your tape measure to extend to vertically, straight across till it reaches the triangular shape of the rafter sloping down. This measurement will give you the slope of the roof. For example, a roof that rises

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An easy guide on how to measure roof pitch accurately.

6 inches for every foot vertically, has a slope of 6 to 12.

Low pitched roofs, particularly in warmer places like Nevada and Arizona, have a pitch of between 2 and 12 and five in 12. The lower the pitch, the more energy-efficient the building will be. And in addition, the cost of the roof construction is less.

Higher pitched roofs, those that have a pitch of 6 to 12, up to the steepest, 12 by 12, are ideal for places that get a lot of snow, ice and rain. The steeper pitch helps the ice, snow and rain drain off better, and also stops extremely heavy snow from accumulating on top of the roof and collapsing from the weight.

For those more daring, the pitch of the roof can be determined by climbing up on a ladder, measuring from the bottom of the roof, or actually climbing from the ladder to the roof itself, particularly if there are uneven surfaces in some of the tiles.

The technique is usually the same, a level, a t-square if measuring from the bottom of the roof, a tape measure, or a couple of long yardsticks taped together.

You may have to measure twice to be sure, but the pitch can generally be determined fairly accurately because in the U.S. at least, there are no half pitches. Even the difference between a 2-inch pitch, which slopes upwards at 9.5 degrees is readily discernible from a 3-inch pitch which slopes at 14 degrees.

Pitch measuring tools

For as little as $7, it’s possible to buy a simple pitch measuring tool. Simply set it on the roof, and it will calculate the pitch with decent accuracy. For continued pitch determination, there are pitch levels that will beep when you have the level ready, and display the pitch with easy to read, blue-dyed read scales. Generally, depending upon the size and the level of accuracy, they run from as little as $25 to around $60.

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The apps

Do you have a smartphone? For a few dollars, you can download a free application to your smartphone, and snap a photo of your roof. Within minutes, using sophisticated

match algorithms, they will send you back a calculation giving you the pitch of your roof.

Satellite roof measuring

In Nashville TN, in 2019 at the International Roofing Expo, was introduced the latest and greatest in measuring pitch as well as other factors that quickly helped a contractor determine exactly how much roofing materials to order and how long it would take to complete the construction. The system uses satellite roof measuring.

The use of satellite measurements contrasted with existing and expensive software which roofers were purchasing or leasing from other companies at up to $2,000 per year.  

Not only does satellite systems work with satellite images which can be obtained for example, from Google, but simple drone images work too, flying a drone overhead of a customers roof, and snapping a few photos is infinitely quicker, cheaper, and more safe than having an inspector climb up on a client’s roof.

In fact, one great advantage of satellite roofing estimates is that if a satellite image exists, a contractor can completely avoid spending up to $100 or more merely to do an onsite inspection of the property.

And if no useful satellite image is available, sending a junior contractor or assistant making $12 an hour and flying a company owned drone over the house, is much cheaper than sending a trained estimator over to the home to get all the details.

Particularly when photo drones that cost a mere $50 and take photos that are sufficient for most satellite imagery estimators to work with, makes this a wise investment, even if they have to pay for satellite roofing reports.

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Why roof pitch is so important

There are four reasons why roof pitch is so important:

  1. Your contractor needs to choose the right materials.  You don’t want heavy snow or wet water to pool on your roof and cause a potential disaster.

  2. Some materials are just not made for the environment you live in.

  3. Local building codes may demand it.  Some cities or even states demand a higher-pitched roof as part of their building codes.

  4. The higher the pitch the more the cost.  Your contractor may pay up to 1.4 times more for a higher-pitched roof, which naturally affects what they charge you. So the better they can estimate what you need, the better for you.
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