The minimum roof slope allowed by code for any type of roof is ⅛-in-12, applicable only to coal tar pitch roof systems. All other flat roof materials require a minimum slope of ¼-in-12, which is why flat roofs are properly known as “low-slope” roofs.
What is the minimum allowable roof slope?
The smallest pitch of a roof is 1/4:12, which translates to 1/4 inch rise to 12 inches of run. Such a small pitch can only work with built-up roofing or specialized synthetic roofing. Covered porches that are near trees or in areas with heavy rains should not be covered with a low-slope roof.
What is the code for roof slope?
For steep-slope roof systems, IBC 2018 provides for a 1:12 minimum roof slope for mineral-surfaced roof roll roofing; 2:12 minimum roof slope for asphalt shingles, photovoltaic (PV) shingles and building-integrated PV; 2 1/2:12 minimum roof slope for clay and concrete tile; 3:12 minimum roof slope for metal roof panels …
What defines a low-slope roof?
A low-slope roof is one that has a slope of less than 3-in-12. This means that for every horizontal foot, the roof level goes up less than 3 inches vertically.
What is the most common roof pitch angle?
The most commonly used roof pitches fall in a range between 4/12 and 9/12. Pitches lower than 4/12 have a slight angle, and they are defined as low-slope roofs. Pitches of less than 2/12 are considered flat roofs, even though they may be very slightly angled.
What is a 4/12 pitch?
A roof that rises 4 inches for every 1 foot or 12 inches of run is said to have a “4 in 12” slope. … The slope ratio represents a certain amount of vertical rise for every 12 inches of horizontal run. For example, a “4 in 12” slope can be expressed as the ratio of 4:12. A “6 in 12” slope is expressed as 6:12.
Which roof pitch is best?
Conventional slope roofs, with a pitch between 4/12 and 9/12, are the most common in residential work. Roofs with a pitch exceeding 9/12 (37 degrees) are termed steep slope roofs. In commercial work, low-slope roofs (with a pitch between 2/12 and 4/12) are most common.
What does a 4/12 roof pitch look like?
A 4/12 is a roof slope that rises by 4 inches for every 12 inches across. This forms an angle of 18.5° between the horizontal section and the roof, and creates a gentle incline that is seen as a midpoint between a low-pitch and medium-pitch roof.
What should a low slope roof include?
That’s why the most common option for low slope roofs are membrane roof systems. Membrane roof systems are sheets, either 5 foot, 10 foot, 20 foot wide sheets of rolled synthetic, water repellent membrane. There are 3 types of membrane roof systems: EPDM, PVC, and TPO.
What should I use for a low slope roof?
Metal roofing systems are popular because of their longevity and durability. Rubber roofs are a top choice for flat or low pitched roofing as it adheres to the roofing materials below it and, when installed correctly, provides a watertight seal to the elements.
What is a disadvantage of low slope roofs?
Disadvantage: Limited Materials
Low slope roofs change how water flows off of the structure. High pitched roofs don’t let water sit, so asphalt shingles and other materials that overlap work well. On a roof with a lower pitch, standing water soaks between these materials.
What roof pitch is 25 degrees?
Roof Slope in Degrees to Standard Roof Pitch Conversion Tables
|Convert Roof Slope from Degrees to Rise-in-Run|
|Roof Angle in Degrees||Roof Slope as Rise-in-Run (X-in-12)|
|25°||5.596 in 12|
|26°||5.853 in 12|
|27°||6.114 in 12|
What roof pitch is 30 degrees?
What roof pitch is 30 degrees? A 30° roof pitch is roughly the same as a 7/12 roof pitch. To convert from degrees to the American ratio: Find the tangent of the angle, tan(angle).