Home Improvement

How to Compute the Pitch of a Roof

The pitch of a roof is not hard to calculate. It is, however, an important number to your house. The pitch of the roof affects the appearance of the structure. Generally, the steeper roofline of a 6/12 roof is considered more attractive than the 3/12 roof that does not seem to rise much beyond a flat roof. Some consider a steeper roof to be more durable when shingled. In spite of this, many homes have a roof that is pitched at about 4/12 because it is safer to work on and makes the house seem slightly wider from the outside. Since all these facts can be a little hard to remember and if you are not that familiar with how all this works it is recommended that you get in touch with professionals like www.rooferinct.net, instead of attempting this on your own. However, if you have some experience here is how you can proceed with this. 

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Get a ladder, a level, a ruler, pencil, and paper to determine the pitch of your roof.

Finding the pitch of your roof does not require any math skills beyond being able to read a ruler and write down the number. If your roof is easily accessible with a lightweight ladder, this is a task that only requires one person and about 5 minutes once the ladder is in place. For higher roofs, get some help to handle the ladder to avoid a nasty fall. The ambulance drivers will not care what the pitch of your roof is.

Secure the ladder and head up to the roof.

With the ladder on solid footing, take the level (at least a 12-inch level) and other items up to the roof. Unless you have a really unusual roof, you should not have to exit the ladder to the roof surface. All of the work can be done from the ladder. The ladder does not have to extend beyond the level of the eaves, but it should reach them.

Pick a relatively clean looking spot to take your measurement.

Mark the level at the 12-inch point from one end. You can do this before going up if you prefer. The level may already be calibrated for use as a ruler. If so, you are good to go. Put the end of the level that is 12 inches from your mark against the vertical center of a shingle or on any point of the roof’s surface for other roofing materials. If you have really strange roofing material, you may need to take the measurement at some other place other than the roof.

Hold the level in the horizontally level position with the bubble centered in the glass.

With the level exactly on the level, use the ruler and measure from the 12-inch mark the distance from the bottom of the level to the roof’s surface. This will be a number between 3 and 12 on most roofs. The majority will measure between 3 and 6 inches. With this number in hand, you can exit the roof. If you do not do much measuring, you might want to take this measurement twice using a different place each time. If the numbers do not agree, go for 2 out of 3 or 3 out of 5 to be sure.

The roof pitch is the vertical rise over the horizontal run.

Since you used 12 inches for your horizontal measurement, determining the pitch will be simple. Whatever number that you measured from the level to the roof is the top number in the pitch. If it was 4 inches, then your pitch is 4/12 and so forth.

Irregular surface roofs may require the measurement to be made in a different spot.

For irregular surface roofs, you can measure from rafters that are exposed beneath the eaves if there are any. You would do the reverse of the roof. Find the level and measure upward instead of downward. You may need to enter your attic and measure from the rafters inside the house. Either way that you get the measure it will still be the distance from the level to the surface over 12.

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