Low Slope Roof Ratio

Slope is conveyed as a ratio and it stands for an amount of vertical rise for every 12 inches of a horizontal run which is again expressed as 3 12 or 3 in 12.

Low slope roof ratio.

Take the measurement of the vertical. Most low slope roofs have a slope of less than 3 in 12 which means that a roof that rises 3 inches for every foot of run will be defined as one that has a 3 in 12 slope. A 4 12 is a roof slope that rises by 4 inches for every 12 inches across. In either case find a professional roofing contractor experienced with low slope roofs and these specific products.

Coffman p e secb and thomas g. Design solutions for building code permitted low slope applications that cause ponding water. Slope is calculated by rise over run thus a low sloped roof is a roof where for every 12 units inches feet or meters measured horizontally run the roof does not increase or decrease by more than 4 units vertically rise. More commonly roll on membranes such that use heat to bond seams together is used as a roofing material.

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. The basic ranges of pitch are not uniformly defined but range from flat which are not perfectly flat but sloped to drain water up to 1 2 12 to 2 12 1 in 24 to 1 in 6. Take a measurement of 12 inches using a level. As in all construction work paying attention to the little details can make all the difference between a long lasting trouble free project and one that results in callbacks and early failure never a good option with a new england roof.

Minimum roof slope of 0 5 12 for lapped nonsoldered seam metal roofs with lap sealant applied minimum roof slope of 0 25 12 for standing seam roof systems modified bitumen roofing should be installed on roof slopes 0 25 12 or greater 2015 irc r905 11 1. Many roofing shingles do not allow applications onto roofs at this pitch. A low pitched roof is anything that is any roof with a pitch of 3 12 or less. Chapter 15 in the 2015 2018 international building code ibc contains installation guidelines that permit a design slope of 1 4 in 12 for certain types of roof covers.

What is the minimum slope for an asphalt shingle roof. Check the surface of the. Conventional from 4 12 1 in 3 to 9 12 3 in 4. The short simple answer is 2 12 has traditionally been considered the absolute minimum acceptable roof slope suitable for asphalt shingles.

Asphalt shingles continue to be the most widely installed roof covering option in north america. Specifically the code text typically reads. A low sloped roof is defined as a slope equal or less than a ratio of 4 to 12. Position your level against the roof until the bubble of the vial sits between two lines.