Definition
What it means.
- Winder turn
- Where a stair changes direction without room for a square landing, builders use winders, triangular treads that fan around the turn. They save space but cramp a move: the inside of the bend offers almost no foothold, and a long rigid item must pivot over treads that are themselves changing width. ItemFits treats a winder turn as a tighter, more constrained bend than a landing turn.
- IRC winder minimum tread depth at the narrow end
- 6 in Source: IRC R311.7.5.2.1 (Winders)
- IRC winder tread depth at the walk line
- 10 in Source: IRC R311.7.5.2.1 (Winders)
In depth
The fuller picture.
Why a winder pinches the carry
A winder replaces a square landing with wedge-shaped treads that fan around the turn, so the tread depth changes across its width. The code (IRC R311.7.5.2.1) keeps the depth at 10 inches where you actually walk, measured at the walk line 12 inches in from the narrow side, but allows it to taper to as little as 6 inches at the inside of the bend. That inside corner is almost no foothold, and it is exactly where a mover wants to plant a foot to pivot.
For a long rigid item the problem is worse than for a person. A landing gives a flat, fixed platform to swing the piece around; a winder gives a sloping, shrinking set of treads with no straight pivot point, so the item has to rotate over ground that is itself changing shape. ItemFits treats a winder as a tighter, more constrained turn than a landing turn of the same nominal width.
Measure it
How to measure.
In practice
How it shows up.
A long sofa that would round a flat-landing turn can bind on a winder, where the pie-shaped treads leave no straight pivot point, the case ItemFits flags as a winder turn.
Go deeper
Related terms and tools.
Frequently asked
Questions we keep getting.
Are winder turns harder than landing turns?
Generally yes, the wedge-shaped treads give no flat pivot, so a long rigid item has less room to swing around the bend.
01How shallow can a winder tread get?
Residential code requires 10 inches of depth at the walk line (12 inches from the narrow side) but lets the tread pinch to as little as 6 inches at the inside of the turn.
02Where does a long item bind on a winder?
On the inside of the bend, where the treads are shallowest and there is no flat platform to pivot a rigid piece around.
03