Calculating Stair Sizes Including string length

1. Calculating Stair SizesIncluding string length Click mouse to bring each point or item in, to work through this example M . S. Martin Randwick TAFE Revised Feb - 2008

2. Calc’s Exercise – Worked ExampleYou may choose to write this down for reference as you work through next slide Specification: • Calculate the quantity of timber required for the open riser stair with following spec: • Rise of flight 850mm • Going of flight 1.100m • String material 250mm x 38mm sawn H/W • Treads 45mm thick sawn H/W • Width of stair 1.200m • Assume rise 160mm

3. Answer – note: this symbol √ below means square root • No. of Risers = .850 .160 = 5.312 say 5 risers • Height of riser = .850 = 170mm 5 • No. of Goings = 4 • Width of going = 1.100 4 = 275mm • Check 2R + G = 550 to 700 =(2 x 170) + 275 = 615 OK • Length of string √(rise of flight)² + (going of flight + one going of step)² √ .850² + (1.100 + .275)² √ .850² + 1.375² √ .723 + 1.891 √ 2.614 = 1.617 • Order 1.8m lengths • String 250 x 38 H/W 1 @ 3.6 • Treads 275 x 45 H/W 1 @ 4.8 (this size is simply to suit going requirement) • You don’t have to show all the working, but for this example it shows you the full answer