Figuring out the slope and pitch of a roof is an important task. Pitch adds to the overall aesthetic of your house, determines how likely your roof is to collect leaves and other debris and even impacts how much moisture your shingles hold. The steepness also can influence the life of your roofthe steepness.
The terms “slope” and “pitch” are often used interchangeably, but there are slight differences between the two:
For the homeowner’s or do-it-yourselfer’s purposes, it’s likely okay to use the terms interchangeably unless you’re installing the roof yourself and specifically need the exact measurement of slope and pitch for some reason.
There are several things you must consider when determining the pitch of the roof — it’s about far more than just the pitch. You also must consider style, materials and many other factors.
Contractors determine the roof pitch by measuring the vertical rise for every 12 inches of the roof. Slopes range from low — about 2/12 slope — to severe slope, about 12/12 slope. The pitch determines what type of roofing materials you can use safely, how well rain runs off the roof and the estimated lifespan of your roofing system.
You should know the pitch of your roof when seeking a quote from a contractor. Of course, they can measure the pitch for you, but if you already know the pitch, it also shows that you’re savvy. This could prevent the few untrustworthy contractors out there from trying to fleece you out of a few extra dollars.
There are several different techniques to measure pitch. The simplest method involves buying a tool called a pitch finder. Place the device on top of a roof or under a rafter in the attic, and it calculates the pitch for you. The tool is fairly inexpensive, and you can find it at hardware stores as well as online.
If you wish to double-check the tool’s accuracy — or you don’t have a pitch finder on hand — you can also manually measure and calculate roof slope. Use a speed square and go inside the attic. Mark a plumb line on one of the common rafters with a level and a pencil. Place the speed square on the plumb line and read the pitch on the square. Measure in several spots to be sure your measurements are accurate.
Most roofing systems come with some type of warranty. Whether you’re using metal roofing or asphalt shingles, each manufacturer has specific requirements, or you risk voiding the warranty. For example, some types of roofing are not compatible with some slopes. Manufacturer warranties clearly spell this out, so make sure you aren’t inadvertently voiding your warranty by using the wrong materials with the wrong slope.
Using the right materials for your roof slope also ensures the roofing lasts as long as possible. A flat roof won’t do well with inexpensive asphalt shingles, for example. Fortunately, most residential homes have a moderate roof pitch.
If you’re measuring to get quotes from contractors for a possible addition to your house, some basic information that might come in handy is knowing how to describe the pitch in general terms. The three diverse types of pitch include:
If you’re adding an addition to your home or attaching a garage, you’ll want to match pitch as closely as possible.
Even if you’re not the one installing a new roof or addition on your home, it’s important to understand the accurate slope and pitch descriptions of your roof. This ensures your contractor uses a product built for your slope of the roof, and thus the replacement lasts longer than if you use a product not meant for that slope.