Commonly used roof pitches were given names such as greek.
													
																	Pitched on roof. 
									
	
		
	
																	The ridge height is 2 9ths to 1 3 the span an angle of 24 to 34. 
																	The pitch of your roof is determined by the measurement of the vertical rise by the horizontal run. 
																	So let s say a roof rises 6 inches for every 12 inches in depth towards the peak. 
																	The ridge height is 1 9 to 1 7th the span an angle of 12 5 to 16. 
															
													
									
	
		
	
																	For every 12 horizontal feet the roof changes 5 feet in vertical height. 
																	The 45 degree roofs seen on a frame houses are 12 in 12 but roofs can be even steeper consider the mansard roofs introduced by french second empire architects in the middle of the 1800s. 
																	A pitched roof is a roof that slopes downwards typically in two parts at an angle from a central ridge but sometimes in one part from one edge to another. 
																	One method to find the pitch is to climb on the roof and measure the rise for a 12. 
															
													
									
	
		
	
																	The rafters equal the span. 
																	The pitch of a roof is nothing more than a ratio that indicates how much rise there is in the roof over a 12 unit horizontal distance. 
																	Another method to find the roof pitch is to go into the attic and measure the rise. 
																	Mansard roofs with nearly vertical faces can boast a pitch of 20 in 12. 
															
													
									
	
		
	
																	Measure from the roof. 
																	Measure from the attic. 
																	The rafter length is 3 4 the span about 48. 
																	The pitch of a roof is its vertical rise divided by its horizontal span and is a measure of its steepness.