How Do I Space Stair Banisters?

Spacing balusters is something you’d like to check before starting – and before buying in order to determine the quantities needed. Well: stair banisters have been around for centuries and the rules for spacing them when have not changed much over the years. 

In the past there were not as many rules and regulations as we have today, but common sense prevailed to what would look good and be safe for the users of staircases. 

Today, there are building codes to follow, but when it comes to spacing stair banisters; they have not deviated much from what we learnt from our forefathers, even those from the ancient world. 

Stair Banister Spacing Calculations

Stair banisters are the supports for the handrail of a staircase.  Besides adding to the beauty of a staircase they are also there for safety since they close the gap between the treads and the handrail. According to the International Residential Code (ICR) standard building codes, the gaps in stair banisters cannot be bigger than 4 inches. 

It is vital to have even spacing of the stair banisters across the whole staircase and this is easy to work out.

1. Measuring for a balcony: The distance from wall to wall, newel post to newel post, or newel post to wall is the balcony distance. The total foot measurement is then multiplied by three to get the total amount of balusters needed for a balcony. 
2. Measuring for a staircase

This is a simple method and the number of steps are counted and multiplied by three (the number of balusters needed per step for treads that are the same size). If the staircase is steeper, each step might only have 2 balusters, with some also having 2 on one side and three on the other. In any event the balusters must conform to the 4 inch rule. When calculating the amount of balusters, opening on the other side must also be considered. 

General rule: Typically, there are 3 balusters per foot. When they are placed, it’s best that one baluster is placed every 4 inches on center, to ensure that there are no bigger gaps. If there is an uneven measurement, the design can be adjusted until the spacing is even on both ends, as long as the 4 inch rule is adhered to. The overhang also has to be taken into consideration.  

1. Measure the depth of each tread to work out baluster spacing 

Residential stair treads are typically 10 to 11 inches each. The minimum required by the IRC is 10, but some states do allow 9 inches. 

There are three methods that can be used to measure. 

• Method 1:

 Either the whole tread can be measured, from the back of the riser all the way to the front of the overhang. Subtract from this measurement the length of the overhang from the riser below to get the proper length of the area where stair banisters can be placed. 

• Method 2:

If the riser is not concealed behind a kneewall, the tread can be measured from riser to riser.  This is done by butting the tape measure to the back riser at the edge of the stair and “eyeballing” the riser below.

• Method 3:

A square can also be used to measure from nosing to nosing and if the overhangs are the same on all the stairs, this is the same as measuring from riser to riser. The square is place on the tread with the vertical arm touching the tread nosing above. A small mark can be made on the lower tread or the tape measure can be hooked on the back of the square and the distance to the front of the nosing can be measured. 

1. Measure the baluster width

This is done by measuring the base. 

1. Calculate the baluster center to center spacing layouts

This is calculated by dividing the tread run by the number of balusters to be placed per stair.

Working out placing of two balusters per tread spacing: 

1^st baluster placing: Subtract the center to center spacing from half of the base measurement. The sum is the position where the first baluster must be centrally placed on the tread, measuring from the back riser. 

2^nd baluster placing: To work out the placing of the second baluster add the center to center spacing and the measurement of the first balustrade placing and this will be the measurement of where the second balustrade must be centrally positioned 

The same process is used for three baluster spacing. 

The StairNation Design Center has been developed to help with baluster choices and counts for any staircase project.