Something to think about!
(Per AlcoLite Ladder)
Smoke is billowing from the second floor window as an elderly woman leans out screaming for help. Two firefighters in full gear start up the ladder. How much weight will the ladder support?

A ladder in good condition at an angle of 75.5° will support 750 pounds. For a building twenty feet tall, the foot of the ladder should be about five feet from the building to achieve the 75.5° angle. 

If the angle of the ladder decreases to 65°, possibly necessitated by the need to clear an overhang, the ladder will now only support 450 pounds. This would be the angle of the ladder if the foot of the ladder was away from a building 20 feet tall by a little less than half the building height. 

If the angle of the ladder decreases to 60°, possibly necessitated by the need to clear a small tree, the ladder will now only support 375 pounds. This would be the angle of the ladder if the foot of the ladder was away from a building 20 feet tall by a little more than half the building height. 
Rule of Thumb
20 ft. wall.......75.5 degrees.......out 5.17 ft.
20 ft. wall.......65.0 degrees.......out 9.32 ft.
20 ft. wall.......60.0 degrees.......out 11.54 ft.
If you are out half the distance of the height, your ladder strngth is near half.