Staircase Dimensions | stair dimensions

Staircase Dimensions | stair dimensions

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Staircase dimensions are an important part of staircase safety.  This page covers all of the important staircase measurements and a mistake to watch out for!

Stair details refer to the standard requirements governing each of the various components of a flight of stairs. Regulated by building codes, especially in conditions serving emergency public egress, stair details specify the height and depth of risers and treads, the widths of stairs for differing occupancy loads, the placement and dimensions of handrails and guardrails, and typical construction methods for fabricating a flight of stairs.

Responding to the movement of the human body, the sizes and relationships of stair risers and treads are regulated to make vertical motion safe and easy. Steep stairs make climbing more tiring and dangerous, while shallow stairs are awkward and inefficient for our human stride.

The tread size (min 10ins / 25.4cm) is dictated by the average adult foot size, although it is not necessary to be able to fit your entire foot on a tread in order for walking up the stairs to be both comfortable and safe.

The riser height (max 7¾ins / 19.7cm) is limited by the way in which we come down the stairs.  If you think about it, you could climb up far more than 7¾ inches very easily and you could climb down far more than 7¾ inches very easily if you are facing backwards.  The rungs of a ladder are placed at more like 12ins / 30cm apart.  But we go down the stairs facing forwards, and it’s this that limits the riser size to being much smaller.

The maximum dimension between balusters is 6ins / 15.2cm.  I don’t know for certain what this is based on, but I’m thinking the idea is that it shouldn’t be easy to get a foot or arm trapped in between a baluster.  Having said that there are plenty of staircase designs where the outer hand rail has bigger gaps or is absent altogether.

rise-vs-run-graph

rise-vs-run-graph

Stair widths are based on the use and occupancy loads of adjacent spaces and must be serviced with handrails on one or both sides depending on the stair width. In general public spaces a minimum of 44” | 112 cm must be met. Handrails must be placed every 60” | 152 cm.

Stair widths

Stair widths

 

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