Building Construction Handbook, Eighth Edition

To check whether the design for winder flights will comply with

recommended dimensions, measurements can be taken from scale

drawings or calculations may be applied.

Calculations ~

Gc = 2Rc (sin ...2)

where,Rc=÷++([W 2 ] E)^22 (V)

Eg. W = 770 mm

E = 150 mm

V=16mm

Rc ([=÷++ 770 2 ] 150 )^22 () 16

Rc=++()385^2150256

Rc (=+ 535 )^2 256

Rc=+== 286225 256 286481 m 535 m

Gc=× 2 535 (sin ) 30 ̊÷ 2

where, sin 30°= 0.5

Gc=×== 1070 (0 5. 2 ) 267 mm

In most applications the winder flight will turn through a 90°angle

on plan. Therefore, the angle subtended by each of three treads

will be 30°, ie. = turn angle...N, where N = the number of winders.

For four winders, =90°...4 = 22.5°.

If the turn angle is other than 90°then = (180 † turn angle)...N.

Eg. Turn angle of 120°with two winders, = (180 † 120)...2=30°.

Refs. BS 585-1: Wood stairs. Specification for stairs with closed

risers for domestic use, including straight and winder flights

and quarter or half landings.

BS 5395-1: Stairs, ladders and walkways. Code of practice for

the design, construction and maintenance of straight stairs

and winders.

Tapered Treads and Winder Flights--2