What are the different terms used in roof slope calculations?

 Let us understand the terms used in roofing slope calculations with the below-given drawing.

1. Rafter:

 The distance between the ridge of the roof to the external edge of the wall surface.

2. Span: 

The horizontal distance between the roof supports up to the bottom end of the roof rafter.

3. Rise: 

The vertical distance between the top end of the wall or roof supports & the ridge of the roof.

4. Run: 

The horizontal distance between the ridge of the roof & the external edge of the top plate of the wall or roof supports.

In other words, the run is half of the total span.

Run = span /2.

5. Pitch: 

The vertical rise over the horizontal run is said as a pitch of the roof. the pitch of the roof is calculated in the number of units it rises vertically for every 12 units of horizontal extension.

For eg., a roof that rises 4 units for every 12 units of a horizontal run has a pitch of 4 / 12.

6. Overhang: 

The extra length of the roof rafter extends beyond the external edge of the wall or roof support.

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