What is the funnel method for stairs?
The funnel method is a tread-balancing technique used for winder and spiral staircases. It is a geometric construction method for dividing the width of the treads so that the stair remains comfortable and safe to walk, even around the bend.
How does the funnel method work?
On a straight flight, all treads are the same width. In a turn, however, the treads rotate, becoming narrow at the newel side and wide on the outside. Without correction, the treads along the walking line would be uneven, which is unsafe to use. The funnel method solves this:
- Along the walking line (the imaginary path of travel on the stair), the tread (going) is divided so that the tread width changes gradually.
- The division is constructed geometrically using a funnel-shaped auxiliary figure, hence the name.
- This makes the turn blend smoothly into the straight parts of the stair.
The result is a staircase where every step has a natural, even pace length.
Application
The funnel method is used when designing and setting out spiral stairs, winder stairs, and quarter- or half-turn staircases. The treads must meet the applicable building regulations for minimum going and safe dimensions. By applying the funnel method, the stair remains pleasant and safe to walk even through the turn, without treads that are too narrow or too wide.
Related terms
- Winder staircase
- Going (tread depth)
- Riser
- Walking line
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