Flat Roof Fall Ratio Calculator

Most roof s have a pitch in the 4 12 to 9 12 range.

Flat roof fall ratio calculator.

Generally such roofs have a pitch ranging from 1 2 12 to 2 12. There are 4 different ways of that are used to specify the slope. The correct minimum fall of a flat roof should be 1 60 by design to acheive 1 80 with deflection ie sagging over time but with flat roofs with a gutter and no internal outlets to worry about over whelming the greater the fall the better. Common roof pitches and equivalent grade degree and radian angles.

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. Fall gradient x distance for example calculate the fall in a 50 metre section of foul water pipework if the gradient is to be 1 in 80. Or 12 drains required. 6m 60 100mm difference between top and bottom.

This applies to general roof areas along with any internal gutters. Learn more about finding the angle of a line using our slope calculator. You can divide roofs into these categories. Drag sliders to animate the results and diagram.

50 000 4 400 11 36. This is because steeper looks tend to fit more with the golden ratio which all architects work by. A gradient of 1 in 80 is converted to a number instead of a. The result is the number of drains needed.

Flat roofs are not perfectly flat in reality they need a small slope for water runoff. A ratio of 1 1 62 is known as the golden ratio and therefore the vast majority of roof pitch in degrees charts you see will be working to this ratio at the very least. Roof pitch is often expressed as a ratio between rise and run in the form of x 12. Flat roof design guide.

For example a pitch 1 12 means that per every twelve yards of building length the rise will be equal to one yard. We can divide roofs into the following categories. The angle of inclination percentage per mille and it can also be expressed as a ratio. The triangle diagram will be re drawn to scale with all dimensions marked.

The ratio is determined to be 1 in n which is different to the mathematical 1 n. According to bs 6229 bs 8217 flat roofs should be designed with minimum falls of 1 40 to ensure a finished fall of 1 80 can be achieved allowing for any inaccuracies in the construction. Often you express roof pitch as the ratio between the rise and the run in the form of x 12. Take the roof s total square footage and divide by the total square footage handled by one drain.