Why the Pitch of a Roof Matters

May 28, 2023

If we asked you to picture a roof, what would be the first thing that came to mind? Chances are, your brain conjured up the image of a traditional gable roof, as you might see on an old-fashioned cottage or barn. Or perhaps you live in a hotter, drier climate, in which case it’s possible you imagined one of the flatter rooftops you are used to seeing. In either case, what cemented the picture you had in your mind’s eye was the pitch of the roof, that is, its slope or steepness.

The pitch of a roof is actually a critical part of its function, although the exact amount of slope that is needed can vary widely depending on the construction of a given building, as well as its geographic location. This article will help you to understand why the pitch of a roof matters, and why the pitch of your roof is an important part of your daily life.

Rise Over Run

If you happen to remember your middle school math classes, you may be familiar with the concept of rise over run. That is, the ratio of the amount a line rises when compared to its vertical length. On a roof, this ratio is written as the number of inches a roof rises for every 12 inches of depth and is referred to as pitch.

As we’ve mentioned, the pitch of a roof is expressed as a ratio, meaning that a roof that rises 5 inches for every foot would have a pitch of 5:12. A conventional roof pitch is usually between 4:12 and 9:12. Anything more than this is considered a steep roof, and anything below it is considered a flat roof.

Most roofs that appear flat are not actually completely flat. That is, they do not have a slope of 0:12. It’s more likely that they’ll simply have a very gradual incline, perhaps 1:12 or 2:12. The reason for this is that having at least some amount of slope is a very important part of roof construction.

Why Do Roofs Have a Pitch?

You can probably guess the main reason why your roof has to have some amount of pitch: to allow a way for rainwater to roll off of the roof without pooling. We have to emphasize why it’s so important to avoid water pooling on your rooftop: water is actually one of the most corrosive substances there is—just think about the Grand Canyon. If it’s allowed to sit, it can eventually wear away at nearly any material, even if that material has been treated to prevent leaks.

When it comes to roofs, even a small leak can be catastrophic. This is because not only does water tend to destroy anything it comes in contact with, but it also encourages the growth of wood-eating funguses that can eventually wear away holes in the roof and even cause it to collapse completely. Constructing a roof with some amount of slope can help to ensure that water doesn’t pool in a way that is damaging to the rooftop.

Different Slopes for Different Folks

If the pitch of a roof is so important, why do flat roofs exist at all? Surely, the greater the pitch, the better protected the roof is from rainfall, right? Well, it turns out that roof pitch is actually a delicate balancing act and depends greatly on the climate in a given area and the purpose of the building.

A roof that is too flat is vulnerable to rain. However, a roof that is too steep may be vulnerable to heavy winds. These winds may pull the shingles off a roof, rendering it vulnerable to moisture. A flat roof can avoid this problem but at the cost of being more vulnerable to rainfall.

The reasons mentioned above are why you are more likely to see flat roofs in states such as Arizona or New Mexico, where there usually isn’t much rainfall. Conversely, parts of the country such as New England or Oregon may have a lot more yearly rain, meaning the roofs there will need to have steeper pitches.

There are other factors, besides climate, that affect the pitch of a roof, too. You may notice that it’s usually only houses that have very steep roofs. Commercial buildings, including apartment complexes, usually have much flatter roofs. The reason for this is that different types of buildings have different needs. A commercial building, for example, will probably have its air conditioning unit installed on the roof. On the other hand, a residential building will likely have its air conditioner installed elsewhere but may also make use of an attic for storage. A roof with a steep pitch can contain a lot of storage space within.

Choose Your Materials Carefully

We’ve explained how the climate affects the pitch of your roof, but we should also explain how the pitch of your roof affects you. It has an important impact on several key elements of your home, such as insulation and curb appeal. It also affects the materials you will need to use in the construction and maintenance of your roof.

If you have a flat roof, it’s unlikely that you will be covering it in expensive decorative shingles, as few people will be able to see them. Instead, you’ll probably need a highly weather-resistant layer of asphalt to protect your roof from both rain and solar radiation. If you have a traditional-looking gable roof, however, you’ll have to take the aesthetics into consideration. You may, for example, choose to opt for colored shingles to give your roof a truly elegant look.

A steep roof is also likely to have a lot of attic space. While this is excellent for storage, it will also affect the insulation of the home. This is because heat radiates upward, and a lot of it can be lost through an attic that isn’t properly insulated, which can drive up your energy bill.

If you have any questions about the pitch of your roof or about the materials you’ll need to maintain it, contact our experts at Interstate Roofing. We will advise you with these and any other roofing questions you may have.