Planning and Dimensional
Information

7 Ft. - 0 In. Diameter, Three Quarter Turn Series, Spiral Stair

Stock Number: USS70-12-3QT
Stair Diameter: 7' - 0" (213.36cm)
Minimum Opening: 88" x 88" (220.98cm x 220.98cm)
Outside Radius: 42" (106.68cm)
Inside Radius: 6" (15.24cm)
Stringer Width, Outer: 11 - 1/4" (28.58cm)
Stringer Width, Inner: 5" (12.7cm)
Stringer Thickness: 1 -1/2" (38.1mm)
Tread Width at Outer Stringer: 16 - 1/2" (41.91cm)
Tread Width at Inner Stringer: 4 - 3/4" (12.07cm)
Tread Thickness: 1 - 1/2" (38.1mm)
Tread Passageway: 33" (83.82cm)
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   Riser   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
>98" 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.
728 / 390 Stair Capacity
lbs. / kgs.
@ 114" Ht.
2570 / 1160

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