Stair Layout With Landings and Winders

A straight run between two bare subfloors is simple math. Real stairs are not bare. Tile goes on at the bottom, hardwood goes on at the top, drywall narrows the width, and the plan turns a corner halfway up. A stair that is 1/2 inch off at the bottom riser is a trip hazard, and it can fail inspection after the finishes are in, when it is costly to fix.

You can already figure rise and run, cut a stringer and drop it for the tread. This guide adds what a lead has to think through before the first cut: finish thickness, the opening, landings, winders and guards. The numbers here come from the model residential code, the International Residential Code (IRC). Secondary copies of recent editions were used, and states and cities change them. Check your adopted edition. The plans and the engineer of record decide how a stair and its landing are supported.

What You Will Be Able to Do

• Figure risers from finished floor to finished floor.
• Set the drop at the bottom and the height at the top for real finishes.
• Work out how long a stair opening has to be for headroom.
• Split a flight around a landing and find its height.
• Check a winder layout at the walkline and at the narrow end.

Start From the Finished Floors

Before you touch a square, find out what finish goes on each floor. Ask, and write it down. This one question prevents most bad stairs.

Worked example. Subfloor to subfloor measures 108-3/4 inches. The lower floor gets 1/2 inch of tile and backer. The upper floor gets 3/4 inch of hardwood.

1. Finished rise: 108.75 + 0.75 - 0.50 = 109 inches.
2. Try 14 risers: 109 / 14 = 7.79 inches. That is over the 7-3/4-inch limit.
3. Try 15 risers: 109 / 15 = 7.27 inches. That works.
4. Treads: 14, because the upper floor is the last tread. At a 10-inch run, the total run is 140 inches, or 11 feet 8 inches.

Bottom and Top of the Stringer

Bottom. The stringer sits on the subfloor, but the finished rise starts on the tile. So the drop is not the full tread thickness.

Drop = tread thickness - lower floor finish

With 1-inch treads: 1 - 0.5 = 1/2 inch.

Top. The difference shows up here too. The top cut of the stringer works out to:

Top rise on the stringer = unit rise + tread thickness - upper floor finish

7.27 + 1 - 0.75 = 7.52 inches, from the last tread cut to the upper subfloor.

Why it matters. Model codes limit the difference between the tallest and shortest riser in a flight to 3/8 inch. If you drop this stringer the full 1 inch and ignore the tile, the bottom riser finishes at 7.27 - 0.5 = 6.77 inches. That is a 1/2-inch difference, which fails.

After the stringers are up, test them before you build anything else. Hold a block the thickness of each finish on the subfloors, and a tread on the cuts, and measure every rise.

Sizing the Opening

The stair opening has to be long enough that a person going down does not hit the header. Headroom is measured plumb from the line of the nosings. The model code asks for 6 feet 8 inches, or 80 inches.

Opening length = (headroom + floor depth) x unit run / unit rise

Floor depth is the distance from the finished upper floor down to the bottom of whatever is at the edge of the opening, including drywall.

Worked example. The upper floor is 3/4-inch hardwood, 3/4-inch subfloor, 11-7/8-inch joists and 1/2-inch drywall.

1. Floor depth: 0.75 + 0.75 + 11.875 + 0.5 = 13.875 inches.
2. Opening: (80 + 13.875) x 10 / 7.27 = 129.1 inches, or about 10 feet 9-1/8 inches.

This is measured level from the top riser line. If a plan shows a shorter opening, the stair may not have the headroom it needs. Work that out before the floor is framed. Moving a header afterward means going back to the people who designed the floor, because the joists around an opening carry extra load.

Warning: A framed stair opening is a fall hazard from the moment the joists go in. Guard it or cover it the same day, and mark any cover. Do not use a stringer as a ladder for material.

Stairs With a Landing

A landing lets a stair turn, and it breaks up a long climb. The model code limits a single flight to a 151-inch rise between floors or landings.

The rise stays the same through the landing. A landing is just a very deep tread in the same stack of risers.

Worked example. Use the same stair: 15 risers at 7.27 inches, with an L-shaped turn after riser 8.

1. Landing height: 109 x 8 / 15 = 58.13 inches above the finished lower floor.
2. Lower flight: 8 risers and 7 treads, so 70 inches of run to the landing.
3. Upper flight: 7 risers and 6 treads, so 60 inches of run.
4. Landing: 36 by 36 inches.
5. Footprint: one leg is 70 + 36 = 106 inches. The other is 36 + 60 = 96 inches.

Work from the full rise, not a rounded riser. An eyeballed 58 puts the error into the risers on each side of the landing. Set the top of the landing framing lower by the landing's finish.

Framing a landing. A landing is a small floor that holds up a stair. The upper flight bears on it, which is a real load on a platform that may not touch a bearing wall. Frame it the way the plans show. If the plans do not show how it is supported, ask. Do not just hang it from wall studs with what is on the truck.

Winders

Winders are wedge-shaped treads that turn a stair without a landing. They save floor space, and they are the easiest stairs to get wrong.

Every winder in a flight is measured at the walkline, so that part of the stair walks evenly. Local rules vary, and some local codes use a different depth.

Why One Pivot Point Fails

The simplest idea is to run all the nosings to one inside corner. It does not work.

Worked example. Three equal wedges turn 90 degrees around a single point. The walkline is an arc with a 12-inch radius.

1. Arc length: 3.14 x 12 / 2 = 18.8 inches.
2. Depth per winder: 18.8 / 3 = 6.3 inches at the walkline.

That is well short of 10 inches, and the narrow end is a point, not the 6 inches required.

A Layout That Can Work

The inside of the turn has to be opened up so each tread keeps 6 inches at its narrow end. Here is a quick estimate for a 36-inch stair and three winders.

1. Inside path: 3 x 6 = 18 inches. That means an inside offset of about 9 inches each way around a newel or a framed block.
2. Outside path: 36 + 36 = 72 inches, so 72 / 3 = 24 inches at each wide end.
3. Depth at the walkline: the walkline is one-third of the way across, so 6 + (24 - 6) / 3 = 12 inches.

That passes, on paper. A straight-line estimate like this only tells you whether the idea fits. Treads are measured square to the nosing, so draw the turn full size on the subfloor. Snap the walkline 12 inches from the narrow side. Mark each nosing and measure each tread at the walkline and at the narrow end. Change the drawing, not the code, until it passes.

Rises do not change on winders. Every rise in the flight stays inside the same 3/8 inch.

Other Limits Worth Checking

Most of these are checked at final inspection, when a change is expensive.

Guard heights on the stair itself vary by edition, so check how yours treats a guard that also serves as the handrail. Plan the blocking for rails and newels before the drywall goes on. A guard post has to resist a real push, so anchor it the way the plan or the rail maker requires. A post lagged into a thin rim or a single stud may not hold.

Finishes eat width. A 36-inch rough opening with 1/2-inch drywall on both sides is already 35 inches. Add a skirt board and it is less. Frame the rough width from the finished width, plus all the layers.

Check the Stringers

Stringers are the beams of a stair. Their span, material and support are not a matter of what fits.

• A cut stringer is only as strong as the wood left behind the cuts. Keep the cuts clean, and do not overcut the corners.
• Use the stringer count the plans show. Treads have limits on how far they can span between stringers.
• Land stringers on solid bearing, and fasten them as detailed. Hangers need to be rated for that use.
• Do not cut a stringer to get around a pipe. Ask.

Common Mistakes

Check Your Understanding

1. Stringers are already set with 7-1/4-inch rises for a bare concrete basement. The owner then adds 3/4-inch hardwood upstairs only. What happens at the top?

The top riser finishes 3/4 inch taller, at 8 inches. That breaks the 7-3/4-inch limit and the 3/8-inch limit on variation, so the stair has to be refigured from the new finished floors.

2. A stringer will sit on tile that is already installed, not on the subfloor. Does the rule change?

Yes. There is no finish left to subtract, so you take off the full tread thickness.

3. A plan shows a 9-foot opening, and your math calls for 10 feet 9 inches. When should that come up, and who hears about it?

Before the floor is framed, and it goes to the people who designed the floor. A short opening may mean the stair lacks headroom, and moving a header changes the load on the joists around it.

4. A landing was framed 1/2 inch low, and both flights are already cut. Which risers does that affect?

The last riser up to the landing shrinks by 1/2 inch, and the first riser above it grows by 1/2 inch. That puts a full inch between them, which fails the 3/8-inch limit. Raise the landing.

5. A winder measures 10-1/4 inches at the walkline and 4-1/2 inches at the narrow end. Does it pass?

No. It meets the walkline depth but fails the 6-inch minimum at the narrow end.

Key Takeaways

• Figure every stair from finished floor to finished floor.
• The drop is tread thickness minus the lower floor finish.
• Work out the opening before the floor is framed.
• A landing is a deep tread in the same run of risers, and it needs real support.
• Measure winders at the walkline and at the narrow end. One pivot point will not work.
• Support and sizing come from the plans and the engineer, not from what fits.