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| The height at the top of the 2nd floor requires that a person must be elevated 11 feet within one 360° turn. | |
| The circular stairwell was divided into 4 quadrants.
The steps start in Quadrant 1. Working up and around the staircase, Quadrant 4 is
located just before the 2nd floor landing.
The first 2 steps in Quadrant 1 are regular rectangular steps; then the circular arc of steps run the rest of the way to the 2nd floor. |
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| To reach the height of 11 feet in exactly 18 steps, a step rise of 7.334 inches is required. |
18 x 7.334" = 132" = 11 ft. |
| The next consideration is headroom. When a circular staircase turns around on itself, the 2nd floor lies over the top of the lower steps. There must be enough headroom so a person doesn't hit his head on the lower decking of the 2nd floor while climbing or descending the lower steps. | |
| Fortunately, the distance between the height of
the 3rd step and the bottom of the 2nd floor decking, turned out
to be a very acceptable 8 ft., 2 inches. ( 7.334" x 3) + 12" = 34.002" then 132" - 34.002" = 98" = 8 feet 2 inches |
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| Next I had to figure the actual lay of the 18 steps.
Steps #1 and #2 are in Quadrant 1 - so is step #18, which is
the 2nd floor.
Quadrants 2 thru 4 form 3/4 of a circle or 270°. Steps #3 thru #17 (i.e., a total of 15 steps) are located in these 3 quadrants. |
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| Thus 15 steps have to be positioned within 270° of a circle. Doing the division shows that each step occupies 18° arc. |
270° / 15 = 18° arc depth for each step. |
| The width of a step from the center of the center pole to the inside of the banister is 3.66 feet (assuming the banister is 4 inches wide). Using the formula for the circumference of a circle, it can be figured that each step will be 1.1498 feet (or 1 ft, 1.8 inch) deep at the outside banister - a reasonable depth for a circular staircase step. (Pi = P = 3.1415) (Radius = R = 3.66 ft.) |
C = 2PR = 22.9958 ft.
(3/4)C = 17.2468 ft. 17.25 / 15 = 1.1498 ft. |
| This is the staircase when drawn (approximately) to the above scale. You see it this way when entering the stairs from the hall to go upstairs. | |
| This is the way it appears when descending from the 2nd floor. | |
| And last, but not least ... the space beneath the steps, in quadrant 4, becomes the hall coat closet by the front door. |