What Is a Roof Pitch & 2 Ways to Calculate It

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beautiful rustic homes with steep roofs

Whether you’re building a house and want to decide on how the roof is going to look like, or you’re interested in finding out more about the characteristics of a roof, knowing what a roof pitch is and how you can calculate it is extremely important. There are many types of roofs out there, according to the roof pitch, and we want to help you identify them by simply calculating this pitch. Which is why we made today’s guide all about the characteristics of a roof pitch and the two main ways in which you can determine it.

What Is a Roof Pitch?

A roof pitch is the numerical measure of a roof’s steepness. This term is used in building construction, and it can also be called slope (a term borrowed from stair construction). The way to calculate it is to divide the vertical rise of the roof by its horizontal span. This element is what makes roofs range from flat to pitched.

The interesting thing is that flat roofs aren’t actually entirely flat. They’re still a little bit sloped so that water can drain from them. Roofs which have a low slope require special building techniques and materials. That’s because you have to make sure you avoid leaks. At the same time, roofs with a steep slope may need additional fasteners.

If you want to find out what the best kind of roof for a house in your area is, you’ll have to consider the amount of rainfall and snow that gets there. That’s because the main purpose of a roof pitch is to redirect snow and water. Which is why if you live in a place where it rains and snows a lot, you’re going to need a home with a steep roof pitch. The roof pitch also determines the kind of materials you’re going to use to build the roof. Furthermore, it regulates how easily you can walk on it, and how the proportions of your house are going to look like.

What Is the Difference Between a Roof Pitch and a Roof Slope?

Before we get into the two ways in which you can calculate a roof pitch (or is it slope?), we thought it crucial to share a couple of details about the difference between a pitch and a slope. Most people, including carpenters and builders, use these two terms interchangeably. However, technically, what you’re measuring using the two methods below is the slope. This is basically the ratio of vertical distance to horizontal one.

If you want to find out the pitch, you should calculate the ratio of the total vertical height of the roof to the total horizontal one. Still, this is not something you practically need, so just finding out the slope is more than enough. Moreover, feel free to use the term roof pitch when you’re calculating the roof slope. Just make sure that if you hire someone to work on your roof, you have the same understanding of this term.

2 Ways to Calculate a Roof Pitch

a roof diagram showing the way it can be calculated

1. Measure the Slope from the Surface of the Roof

The first thing you have to do before calculating the roof pitch of your home is make sure you can safely walk on the roof. If the roof is extremely steep, damaged, wet, or covered in ice, you shouldn’t attempt this. Also, check the roofing material to ensure it’s not too loose, gritty, or slippery.

Keep in mind that if the roof contains curled shingles or isn’t entirely flat, your calculations won’t be as accurate. In order to avoid this, measure starting from the rake board that you can find at the roof’s edge. In terms of tools, you’re going to need a carpenter’s level, a marker, a tape measure, and some paper.

First, take the carpenter’s level and measure 12 inches on it, highlighting it with the marker. Then, position one of the level’s ends against the roof. Don’t forget to make sure the bubble of the horizontal vial stands exactly between its two lines. Using the tape measure that you place with the 0 mark against the roof, measure the distance from the level to the roof. Keep in mind that the tape has to be perpendicular to the level. Moreover, it has to meet it at the 12-inch mark you made earlier. Finally, mark the tape with the vertical distance.

In order to actually calculate the roof pitch, you have to figure out the ratio of the rise over the run (basically vertical over horizontal). So, if you have a 12-inch run and a 6-inch rise, the roof pitch will be 6:12.

2. Measure the Slope from the Rafters

This is one of the most accurate methods through which you can calculate a roof pitch. Moreover, measuring the roof’s underside is not at all difficult either. What you have to do is take a carpenter’s level and position one of its ends against the rafter’s underside. Adjust it until the bubble is positioned in the middle of the two lines. Then, measure 12 inches on it and mark it.

With the tape measure, you’re going to check the vertical distance between the level and the rafter. First, place it perpendicular to the level. Then, find out what the distance between the mark you just made and the rafter’s underside is. Finally, take that distance and calculate the roof pitch using the same method we mentioned above. So, if you get a rise of 4 inches, your roof pitch is 4:12.

Finding out the pitch (or slope) of your roof is important when choosing the roofing materials, when making sure how well the roof will perform, and when deciding on the aesthetics of your home. We hope today’s guide to two of the best ways in which you can calculate a roof pitch managed to prove that this process is not a difficult one. As long as you take all the safety precautions, you have to, and you keep in mind the tips we provided you with, you’re going to be able to find out the pitch of your roof in no time.

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