the underside of a stair

outer projecting edge of a tread

a sloping member which supports the steps in a stair

a vertical member between two treads

balusters

newal posts

balustrades

railings

10

12

15

no limit

2

3

5

no limit

300 to 350 mm

400 to 450 mm

500 to 550 mm

600 to 650 mm