Planning and Dimensional
Information

6 Ft. - 6 In. Diameter, Three Quarter Turn Series, Spiral Stair

Stock Number: USS66-12-3QT
Stair Diameter: 6' - 6" (198.12cm)
Minimum Opening: 82" x 82" (205.74cm x 205.74cm)
Outside Radius: 39" (99.06cm)
Inside Radius: 6" (15.24cm)
Stringer Width, Outer: 11 - 1/4" (28.58cm)
Stringer Width, Inner: 5" (12.7cm)
Stringer Thickness: 1 - 1/2" (38.1 mm)
Tread Width at Outer Strin-ger: 14 - 1/2" (36.20cm)
Tread Width at Inner Stringer: 4 - 3/4" (12.07cm)
Tread Thickness: 1 - 1/2" (38.1 mm)
Tread Passageway: 30" (76.2cm)
Handrail Width: 3 - 1/2" (8.89cm) - Opt. 4 - 1/2" (11.43) or 5 -1/2" (13.97cm)
Handrail Thickness: 1 - 1/2" (38.1 mm)
Baluster Spacing: Approx. 6" (15.24cm), - Opt. 4" (10.16cm), or alternating 2", 3", 2"
Turn per inch of Rise: 2.857 Degrees
Rise per Degree of Turn: 0.35" (8.89mm)

Floor to Floor  

Risers

Degrees of Turn

74" to 82" (187.96cm to 208.28cm)

9

188 to 208 Degrees

>82" to 90" (208.28cm to 228.60cm)

10

208 to 231 Degrees

>90" to 98" (228.60cm to 248.92cm)

11

231 to 255 Degrees

>96" to 106" (248.92cm to 269.24cm)

12

255 to 278 Degrees

>106" to 114" (269.24cm to 289.56cm)

13

278 to 301 Degrees

>114" to 122" (289.56cm to 309.88cm)

14

301 to 324 Degrees

>122" to 130" (309.88cm to 330.20cm)

15

324 to 347 Degrees

Tread Capacity
lbs. / kgs.
717 / 325 Stair Capacity
lbs. / kgs.
@ 114" Ht.
1724 / 782

Specifications for heights up to 190" (4.83m) are available upon request.