As you may have noticed, in the United States, roof slope is usually expressed as x:12. The slope should always be noted in elevation and section views; it is optional to note it in plan view. In plan view, it is a simple open arrow indicating the slope's direction. The angle of the arrow is proportional to the degree of slope.
In this article, we will discuss how to show roof slope on a building plan or other plan view drawing.
First, find the highest point on the roof. Usually, this is either at the peak of the roof or in the middle between the peaks. You can use any horizontal line as a reference for the height of the building. Now draw a vertical line from one end of the building to the other. This will form two angles with the ground. If you were to connect each corner of the building to its corresponding corner on the vertical line, these lines would form a diamond pattern. Each angle of the diamond is 90 degrees. They intersect at the highest point on the roof.
Now that you know where to find the highest point on the roof, you can indicate the slope of the roof by using an angled arrow. The longer the arrow, the steeper the slope. Use a meter stick or ruler to ensure that you create an accurate representation of the roof slope.
You can also express the slope of the roof in degrees.
Slope: the angle of inclination of a roof surface, expressed as a ratio of the rise (in inches) to the run (in feet). The word "slope" is also used to describe the horizontal distance between two points on a land surface. The degree of slope is called its pitch.
There are three types of slopes: level, rising and falling. A level slope begins at one end of the building and continues to the other without any change in height or grade. A rising slope gets steeper as it goes up. A falling slope gets flatter as it goes down.
The amount of slope a roof takes is called its pitch. Slopes are usually described by their rise over their run. For example, a four-inch rise over twenty-four inches of run results in a 1:12 slope. This means that if you were to draw a line from one end of the roof to the other, the top of that line would be raised 1 inch for every 12 inches of run length. Some people call this a steep slope because it takes more effort to climb than a flat one. Other names for different pitches are ladder, mild, moderate and steep.
The type of material used to build the roof affects how it will hold water. Flat roofs are made of asphalt or concrete.
Roofs with a low slope
| Roof Gradient | Degrees | Percent |
|---|---|---|
| 1/2 : 12 | 2.39° | 4.17% |
| 1 : 12 | 4.76° | 8.3% |
| 2 : 12 | 9.46° | 16.67% |
| 3 : 12 | 14.04° | 25% |
A low-slope roof is one with a slope of less than 3:12, or 25%. A steep-slope roof is one with a pitch of 25% or higher. Sloped roof coverings are classified into three types: thatch, shingles, and architectural sheet metal. The type of covering on your roof determines how it will affect your home's energy efficiency and appearance.
The grade of your roof directly affects how water moves off of it. The steeper the roof, the faster water drops away from its surface. This means that more water can be removed from your house using the roof's air space instead of leaking inside. Steep roofs are also easier to clean because any dirt or debris that gets on them can be swept off rather than being trapped under lower-sloping surfaces.
Low-slope roofs are the most common type of roof in North America. They're easy to install and maintain and come in a wide variety of shapes and styles. The main disadvantage of low-slope roofs is their appearance - they look like flat surfaces when they're actually sloped at up to 3 inches for every 10 feet. If you want your roof to look like its supposed to (i.e., be sloped) but still provide adequate protection from the elements, choose a low-slope material option.
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 with a pitch greater than 9/12 are referred to as steep slope roofs. They're more common on commercial buildings and other structures where water resistance is important.
Slope roofs are named for their resemblance to the blades of a snowmobile. The number after the decimal point indicates the ratio of vertical height to horizontal width of the roof. So, a 4/12 slope means that there are four units per foot of roof height and twelve feet wide. A 1/4 slope is twice as much material needed for the same amount of surface area (since the total area under a curve is constant). A 3/8 slope is about three times as much material as a 4/12 slope. A steeper slope requires less material overall while still providing adequate coverage.
The choice of roof pitch affects how much material you need and how fast it will drain. If you live in an area that gets a lot of rain, or if you plan to keep any livestock on the property, a shallower pitch may be better for your wallet and the environment. Otherwise, a steeper pitch will make your roof last longer and require fewer repairs over time.
As long as you choose your roof pitch wisely, it shouldn't be a problem.
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