How to Read Stairs on a Floor Plan
Learn how stairs are drawn on a floor plan: the break line, arrows, and riser marks, so you can read any staircase symbol with confidence.
A staircase on a floor plan is drawn as a series of parallel lines running between two floor levels, with a diagonal or curved break line cutting across them and an arrow labeled "UP" or "DN" showing which way you're headed. Each of those parallel lines is one step, or riser, and once you know that, a set of stairs stops looking like a confusing tangle of lines and starts looking like exactly what it is: a path from one floor to another.
This guide walks through every part of that symbol, the different stair shapes you'll run into, and how stairs are handled when a plan covers more than one story. If you haven't read a floor plan at all yet, it's worth starting with what a floor plan actually is before diving into a feature as three-dimensional as a staircase.
What a Staircase Symbol Actually Shows
Because a floor plan is a flat, top-down slice through a building, it can only show what's happening at one specific height. A staircase is a problem for that kind of drawing because it physically occupies several different heights at once as it climbs from one floor to the next. Drafters solve this with a few conventions that show up on almost every plan:
- Parallel lines (the treads). Each line across the width of the stair represents one step. Count them and you're counting risers.
- A break line. Partway up the run, you'll see a diagonal line, a zigzag, or a wavy line cutting across the stair. This marks the point where the stair rises above the "cut plane" of the floor plan, meaning the drawing can no longer show what's physically there because it would be above your head at that point. Everything below the break line is the visible stair; everything above it is implied.
- An arrow with UP or DN (or DOWN). The arrow tells you whether that run of stairs takes you to the floor above (UP) or the floor below (DN). On some plans you'll see both labels near the same stairwell if it serves both directions.
- A note or label, such as "STAIR 1" or "MAIN STAIR," especially in larger buildings with more than one staircase.
For more on plan symbols in general, see the guide to reading a floor plan.
Reading the Arrow and the Break Line Together
The arrow and the break line work as a pair, and reading them together tells you the story of the stairs.
Picture a straight staircase drawn on the ground-floor plan of a house. The bottom of the run starts at floor level, where you'd actually be standing. As the lines climb up the page, they represent you climbing higher. At some point, usually near the middle of the run, the stair passes above the height where the plan's imaginary horizontal cut is made. That's where the break line appears. Above it, the plan can no longer show the stair as it physically exists, so the drafter draws it lighter, dashed, or simply stops the tread lines and continues the arrow to its destination.
The arrow tells you which direction is "forward" along that run. An arrow labeled UP means walking that direction takes you to the next floor up. An arrow labeled DN means the stair drops down to the level below.
A simple check: stand at the bottom of the stair in your mind, follow the treads toward the break line, and read the label at the arrowhead. That's your destination.
Common Stair Shapes and How They're Drawn
Not every staircase runs in one straight line, and the plan view changes shape along with the stair itself. Here's how the most common layouts appear from above.
| Stair type | How it looks on the plan | What to notice |
|---|---|---|
| Straight run | One continuous set of parallel lines from bottom to top | Simplest to read; break line usually falls near the middle |
| L-shaped (quarter turn) | Two straight runs meeting at a right angle, often with a small square landing at the corner | The landing is drawn as an open rectangle with no tread lines inside it |
| U-shaped (half turn) | Two parallel runs that double back on each other, connected by a landing | Follow the tread lines carefully; two runs can look like one wide stair if you're not paying attention |
| Winder stairs | A run where the treads narrow and fan out at a turn instead of using a flat landing | The treads look pie-shaped or wedge-shaped at the turning point |
| Spiral stairs | A tight circle or curve, usually shown as a fan of thin wedge-shaped treads around a small central circle (the center post) | Common in small spaces; check the plan notes for the direction of the spiral |
Landings
A landing is a flat resting spot partway up a stair, drawn as a plain rectangle or square with no tread lines running through it. If you see the parallel lines stop, an open shape appear, and then the tread lines pick up again at a different angle, that open shape is a landing, not a mistake in the drawing.
Handrails and Guards
Many plans also show a thin line running alongside the stair, offset a short distance from the tread lines. That's the handrail or guard along the open side. It's a useful cue for figuring out which side of the staircase is open to the room below and which side sits against a wall.
Stairs That Connect More Than One Floor
On a set of plans for a multi-story building, stairs get more interesting because the same physical staircase appears on more than one sheet. The ground-floor plan shows the bottom of the stair with an UP arrow, and the second-floor plan, drawn on its own separate sheet, shows the top of that same stair with a DN arrow in roughly the same location.
A few things worth checking when you compare stairs across floors:
- Do the arrows point the right way relative to each other? The floor below should show UP; the floor above should show DN, at the same footprint.
- Does the stairwell line up in the same spot on both plans? A stair opening has to sit in the same horizontal position on every level it passes through, so compare dimensions from a fixed wall to confirm they match.
- Is there a second staircase? Larger homes and most commercial buildings have more than one, often labeled to keep them straight, so don't assume every UP arrow belongs to the same stair as the DN arrow on the level above.
Basements and attics get the same treatment: a basement plan usually shows a DN arrow leading up out of it, and an attic or loft plan shows the stair arriving from below with no further run above.
Quick Checklist for Reading Stairs on Any Plan
- Find the parallel lines. Each one is a step, so count them if you want to know the number of risers.
- Locate the break line. It marks where the stair rises out of the plan's view.
- Read the arrow and its label (UP or DN) to know the direction of travel.
- Look for an open rectangle mid-run. That's a landing, not a gap in the drawing.
- Watch for narrowing, wedge-shaped treads. That's a winder or a spiral, not an error.
- Check the same stairwell location on the plan above or below to confirm the run continues where you expect.
- Note any labels ("STAIR 1," "MAIN STAIR") if the building has more than one staircase.
Once stairs make sense, it's worth reviewing door and window symbols next, since those elements together make up most of what you'll be decoding on a typical floor plan.
Frequently Asked Questions
Why do stairs have a diagonal line cutting across them on the plan?
That diagonal (or zigzag, or wavy) line is the break line. A floor plan is a horizontal slice through the building at a set height, and a staircase rises up past that height as it climbs. The break line marks where the stair goes above the level the plan can show, so everything past it is implied rather than drawn in full.
How do I know if stairs go up or down from a plan?
Look for the arrow drawn along the run of the stair. It will be labeled UP or DN (sometimes DOWN). The label tells you where that run takes you relative to the floor you're looking at, so the same physical staircase can show UP on the lower floor's plan and DN on the upper floor's plan.
How can I tell how many steps a staircase has from the plan?
Count the parallel lines drawn across the width of the stair run, including any dashed or lighter lines past the break line. Each line represents one riser. Some plans also include a note with the total riser count, which is worth checking against your own count.
What's the difference between a landing and a gap in the stair drawing?
A landing is drawn as a plain, open rectangle or square with no tread lines inside it, usually where a stair turns a corner or takes a short breather partway up. It isn't a missing piece of the drawing; it's an actual flat platform you'd walk across. If the tread lines resume on the other side at a different angle, you're looking at a landing connecting two runs.
Are stair dimensions on a floor plan enough to build from?
No. A floor plan gives you the general shape, direction, and footprint of a staircase, but exact riser height, tread depth, headroom, and railing requirements are governed by local building code and usually detailed further in sections elsewhere in the drawing set. Confirm the specifics with your local building department, and have a licensed architect or engineer review any plans you intend to build from.