How to Fit Winder Stair Treads

Find out what the local building codes are for residential staircases, including standard treads and winder treads. Most codes require a winder tread to be at least 6 inches wide at its narrow end, and 9 or 10 inches wide along its walk line, an imaginary line located 12 inches in from the tread’s narrow end.

Use building code standards and the dimensions of your space, including wall length and landing height, to calculate the unit run of the bottom section of stairs. The codes will specify the minimum width and depth of each tread and the height of each riser, allowing you to calculate how many stairs you’ll need to reach the landing.

Make a large-scale plan view drawing of the entire staircase. Draw the outside lines of the case first to render its basic shape. A staircase that turns on a 90-degree angle will be L-shaped, while a staircase that turns on two 90-degree angles will be U-shaped. If your staircase turns on an acute angle, the plan view will resemble a more open L-shape.

Draw lines representing each tread of the first section of stairs, starting at the bottom of the case. Straight staircases are comprised of uniform treads, so your lines should be evenly spaced. The line dividing the last straight tread from the first winder tread should intersect the line of the stringer below its angled turn.

Use the minimum measurements required by your local building codes to lay out the winder. Most winder staircases turn a 90-degree angle and have three evenly spaced winder treads. Stairs that turn on an acute angle typically have two evenly spaced winder treads.

Mark the inside stringer line with dots to indicate the narrow end of each tread. Most codes indicate that these sides should be at least 6 inches long. Ensure your measurements are done to scale for complete planning accuracy.

Set the point of your compass at the inside corner of the staircase to mark out the winder’s walk line. Because the walk line is 12 inches in from the narrow end of the treads, a full-scale drawing would require you to swing a 12-inch arc to connect the walk lines of the lower and upper cases.

Divide the walk line into the necessary number of winders, using code-specified measurements. A full-scale plan where building code specifications state that a winder walk line must be 10 inches wide, for example, requires you to mark the walk line every 10 inches.

Use a yardstick or framing square to connect each inside marking with its opposing marking on the walk line. Carry each line through to the opposite stringer line to mark out the full tread. Stairs turning a right angle should only have three winder steps, and the line dividing the top winder tread from the first tread of the upper section should run parallel to the rest of the upper treads.

Lay out the upper portion of stairs to the top.