This measurement is best done on a bare roof because curled up roofing shingles will impair your measurement.
1 2 inch slope roof.
If a roof slope rises say 4 inches when measured 12 inches along the bottom of a horizontal roof truss.
The table below shows common roof pitches and the equivalent grade degrees and radians for each.
The most common rafter spacing is 24 inches and 5 8 inch plywood is recommended for that.
Flat 0 in 12 to 2 in 12.
Slope conversion tables 1 4 1 2 3 4 1 1 1 4 1 1 2 1 3 4 2 2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 0 25 0 50 0 75 1 00 1 25 1 50 1 75 2 00 2 25 3 4 5 6 7 8 9 10.
Most roof s have a pitch in the 4 12 to 9 12 range.
We can divide roofs into the following categories.
Low pitched roofs are generally difficult to maintain and you need special materials to prevent leaks.
A pitch over 9 12 is considered a steep slope roof between 2 12 and 4 12 is considered a low slope roof and less than 2 12 is considered a flat roof.
The triangle diagram will be re drawn to scale with all dimensions marked.
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Roof slopes slope rise run in inches conventional slope 4 in 12 and up.
What exactly is roof slope.
Flat roofs are not perfectly flat in reality they need a small slope for water runoff.
A 2 12 roof slope means your roof has 2 inches of vertical drop for every 12 inches of horizontal distance.
These roofs have a pitch less than 4 12.
The picture below shows the pitch of a 7 12 roof slope meaning that for 12 of horizontal measurement roof run the vertical measurement roof rise is 7.
For rafters spaced 20 or more inches apart 1 2 or 5 8 inch plywood is recommended.
The slope ratio represents a certain amount of vertical rise for every 12 inches of horizontal run.
If the rise is 6 inches for every 12 inches of run then the roof slope is 6 in 12 the slope can be expressed numerically as a ratio.
A roof that rises 4 inches for every 1 foot or 12 inches of run is said to have a 4 in 12 slope.
Low slope 2 in 12 to 4 in 12.
Enter run the flat level length then click pitch angle or rise to select then enter other known dimension angle or pitch.
Generally these roofs have a pitch from 1 2 12 to 2 12 from 4 2 to 16 7.
Flat roofs which aren t perfectly flat require a small slope to allow for water runoff.
Generally such roofs have a pitch ranging from 1 2 12 to 2 12.
That means the roof doesn t shed water as easily as steeper roofs which is why choosing the right type of roofing material is so important.