For most home styles, roof pitches fall into a range of 4/12 (a moderate) slope up to 8/12 (fairly steep). Examples of extreme slopes range from 1/4 (almost flat) to 12/12 (sloping down at a perfect 45-degree angle). Most roofs are between these two extremes, with an average grade of 6 or 7.
The best way to determine the angle of your roof is with a protractor. First, measure up from the middle of the house to the highest point on the roof. Multiply that number by 0.5. That will give you the slope of the roof in degrees. For example, if your measurement is 100 feet and it takes half as much distance to go around the house than up the side, then the slope is 30 degrees.
There are several types of roofs: flat, gable, hipped, mansard, shed, and tile. Each type has its advantages and disadvantages. It's best to work with a professional when choosing a roof for your home. He can help you decide which type of roof is right for your situation and design preferences.
Flat roofs are usually made out of asphalt or concrete. They are easy to maintain and durable. The main disadvantage of this type of roof is that they are not visible from the street. You will need to add other forms of decoration to make the roof appear attractive.
A "steep roof" is defined by OSHA as any roof with a rise/run ratio greater than 4:12. (18.43 degrees). While most standard-pitched house roofs seldom surpass a 12:12 pitch (45 degrees), the landscape is occasionally distinguished by a design that harkens back to a time when far higher roof pitches were more popular. Such roofs are generally called "steep" or "high-pitched."
The maximum allowable slope of a roof is determined by the height of its peak above ground level. The National Electrical Code requires that all roofs be no more than 10 percent slope, but many builders and architects choose to have their roofs be slightly steeper than this, especially if they are made of metal. A roof that is too steep causes water to run off quickly, which can cause erosion and damage to nearby property.
The term "slope" refers to the angle between the horizon and the roofline. If you look at a map, you'll see that some places have hills, while others are flat. The amount of hill or drop off from one side of the road to the other determines how steep or flat an area is. If you drive up a driveway on a hill and there's nothing to indicate what type of surface it has, you might want to wait until you get inside to find out if it's paved or not.
Roofs are usually described by the number of inches per foot (IPF) that they rise from front to back.
On residential roofs, conventional slope roofs are the most popular. On most properties, this implies the slope has a pitch of 4/12 to 9/12. Roofs having a pitch greater than 9/12 are referred to as steep slope roofs. They're more common on commercial buildings and other large structures where they provide better insulation and coverage for other features such as solar panels or other forms of renewable energy technology.
The next most common type of roof is called a hip roof. Hip roofs are flat except at the ends where they have a slight slope to allow water to run off. Hip roofs are used when there is no need for the building's sides to face upward like on a traditional shingle style roof.
A gambrel roof is similar to a hip roof but with two differences. First, the end walls are never flat but always angled slightly downward. Second, the middle wall is not flat but instead has an inwardly curved top section followed by two straight sections. The purpose of the curved part is to create more space inside the roof for warmer air to flow up from below through vents in the ceiling into the attic area.
A shed roof is only one floor high; it usually has a gable end on at least one side. The roof is flat except for a small peak that may be shaped like a half-cylinder, a triangle, or another simple design.
Depending on the roofing material, low-slope roofs generally have a minimum slope of one-fourth inch vertical to twelve inches horizontal (or 1/4:12 or 2%). Roofs with a 3:12 pitch are termed low-slope. Traditionally, low-slope roofs were erected using an asphalt built-up roof covering. Today, they can be made from many materials including steel, aluminum, and plastic.
The typical residential low-slope shingle has a slope of approximately five degrees. This means that for every 100 feet of height, the roof will extend about 50 feet horizontally. Low-pitched roofs are usually between 7 and 10 years old when replaced. Older or newer roofs may not provide as much protection against heat and rain as does a well-designed low-pitched roof.
Modern building codes require low-slope roofs to prevent water from flowing off the roof into interior rooms or walkways. This prevents damage to furniture, floors, and other items as well as creating a safety hazard if it flows onto pedestrian areas or into driveways. The National Roofing Association reports that half of all sloped roofs are low-pitched.
Low-pitched roofs are used in many different applications including houses, schools, churches, clinics, hospitals, commercial buildings, and factories. They are also used on military bases and government facilities. These roofs are commonly designed with a metal deck attached to walls with openings for windows or doors.