It may seem simple, but the modern roof is actually a marvel of engineering and the culmination of centuries of technological innovation. The roof, after all, is the first line of defense a building has against the elements. It must keep out rain, snow, cold air, hot air, and ultraviolet radiation. It must be resistant to the buildup of sticks, leaves, and other detritus that might otherwise compromise the roof and lead to leakage. It must also be aesthetically pleasing, as this can have an important impact on the value of a building.
One of the most important elements of a successfully designed roof is its pitch. But what is the pitch of a roof? How is it determined? Why is it so different for each roof? Read on to find out.
Parts of a Roof
The overall structure of the roof begins with layers of plywood known as decking. The decking is what gives the roof its shape, although it’s not, in and of itself, particularly strong. It must have a lot of other materials attached to it to be a proper roof.
The next layer is referred to as underlayment, which is a felt material that acts as an extra line of defense, protecting the roof from further intrusion from the elements. Shingles are placed on top of this material. The shingles may be made from any number of different materials. The most common are asphalt shingles, which are inexpensive and lightweight. However, wooden and composite shingles are also common. Somewhat less common are slate shingles, which are heavier and more expensive, although they can certainly boost the curb appeal of a home that features them.
The Pitch: One of the Most Important Design Elements
While the standard parts of the roof may not differ much from roof to roof, one aspect of design that can vary greatly is the pitch. What is the pitch of a roof, though? In simplest terms, it’s the angle of the roof. It is expressed as a rise over run equation, with the rise corresponding to 12 inches of run, or depth, on the roof.
The pitches vary quite widely, and there are several reasons for this. The local climate is a major factor. Areas with heavy rain and snowfall are likely to have very steep roofs, as this allows the water and snow to roll off the rooftop easily. Areas of low rainfall and lots of sun are likely to have flatter roofs, as these are more efficient if there isn’t a lot of inclement weather to defend against. Flatter roofs are also more efficient in high-wind areas. Otherwise, the wind may carry shingles away and necessitate costly repairs.
Why Do You Need to Know the Pitch?
Knowing the pitch of your roof is important for several reasons. Chief among them is the fact that the pitch has an important effect on the drainage of water from the roof. The slope of the roof also influences what materials you will use in the construction of the roof. Steeper roofs make use of asphalt shingles, while flatter roofs may simply make use of an additional layer of underlayment to protect from the elements.
The roof pitch also has an effect on the overall durability of the roof. Generally, roofs will last for many years, but this will depend on how they are constructed, as well as how they are maintained.
How To Determine the Pitch of Your Roof
It is possible to determine the roof pitch of your own home with just a handful of common tools: a level, a pencil, and a tape measure. You’ll be measuring the rise over the run, which you can do from within the attic. You simply need to enter the attic and hold the level against a roof rafter. From there, measure straight up from the 12-inch mark on the level.
By making a measurement at the 12-inch mark, you can determine how much rise there is for each horizontal foot of distance. Once you have determined this, you can mark the slope, or pitch, down. It should be written as the number of inches in the rise over 12. For example, 4:12 is a common pitch. This ratio means the roof rises 4 inches for every 12 inches across.
Is It Possible for a Building to Have No Slope?
Some buildings, of course, have nearly flat rooftops. Apartment buildings and commercial buildings are among the most obvious of these. However, even these buildings do not have entirely flat rooftops. They still need to be able to drain away water, which means they usually have a pitch of anywhere from 1/2:12 to about 3:12.
If a roof was completely flat, water would pool on top of it, ultimately allowing the water to seep through and cause water damage inside of the building. That said, there are many dead flat roofs in the Portland/Vancouver Metro area. In these cases, slope can be created by use of tapered insulation during the reroofing process. Even a small amount of slope can help to prevent this.
Importance of Maintaining Pitch
Regular maintenance and repair are important for any roof, particularly one that is regularly subject to wind and weather. A roof with a higher slope may be more vulnerable to wind, but if the shingles of the roof are carried away by any wind, the bare patch may then allow rain and snow to enter the home.
Yearly maintenance and repair will help to prevent the loss of shingles as a result of heavy weather. Contact a roofing contractor such as Interstate Roofing and request a quote for a maintenance visit.
