How to calculate spiral staircase balustrading
In the UK most spiral staircase kits use vertical spindles in their guard rail designs. It is important to ensure you use the correct spacings between spindles so that the railing can be used safely. The building regulations state that there should not be a gap greater than 100mm between spindles. To make calculating the number of spindles straightforward, and to comply with the regulations, we use a gap of 99mm maximum for our examples below.
1. Firstly, measure the length of the gap that you wish to fill with your guard rail or balustrade.
2. Next, deduct 99mm from your total measurement. Then divide the result by the width of a spindle plus the maximum spacing allowed. For example, if your balustrade is 1250mm long, and spindle spacing is a maximum 99mm, and spindle width is 22mm, the formula would be (1250 - 99) divided by 121mm (which is your 22mm spindle plus 99mm spacing) = 9.5 spindles. This is then rounded up to the next whole number, 10. So in summary you need 10 spindles to fill a balustrade length of 1250mm.
3. To give the best aesthetic results you should space the spindles equally in the run of balustrade - they don't need to have the same spacing as on the spiral staircase, by the way. Simply multiply the width of each spindle by the number of spindles in the run, in our example this is 10 no. Subtract the result from the total length of the run of balustrade.
10 x 22mm diameter = 220mm, where 10 is the number of spindles and 22mm the width of each spindle
1200mm minus 220mm = 980mm, the total space left.