How to Build Stairs

Building a safe, sturdy, and code-compliant set of stairs looks complicated, but when you break the process down step-by-step, anyone with basic carpentry skills can do it. In this blog, you’ll learn how to build stairs from scratch, including how to calculate your rise and run, how to lay out and cut stringers, how to build a landing, how to verify head clearance, and how to assemble everything securely.

1. Before You Start: The Basics of Stair Building

Before cutting a single board, you need to understand a few essential concepts. These determine how tall each step is, how deep every tread needs to be, and how your stairs will fit into the space.

1.1 Check Your Local Building Codes

Always start by checking building codes in your area. Most regions follow similar rules, but there can be small differences. Common code requirements include:

• Maximum riser height: often around 7¾ inches

• Minimum tread depth (run): often 10 inches

• Minimum headroom: usually 6 feet 8 inches

• Landing size requirements

These rules prevent steep, unsafe, or awkward steps.

1.2 Know Your Finished Flooring Thickness

One of the biggest mistakes people make is forgetting to factor in the flooring thickness at the top and bottom of the stairs. Your rise measurement is taken from finished floor to finished floor — not just raw framing.

For example:

• If you have hardwood (¾ inch): add that thickness.

• If you have tile (½ inch): add that thickness.

• If you’re building in a garage with bare concrete: no adjustment needed.

In the project demonstrated, the floor was concrete below and the subfloor above was already the finished surface. So the measurement could be taken directly.

2. Step One: Measure the Total Rise

The total rise is the vertical measurement from the bottom floor to the top floor.

In the project example, the total rise was:

• 123 inches from concrete to the top finished floor.

This number determines everything else in your stair design.

3. Step Two: Determine Your Stair Run Distance

After knowing how tall the stairs must be, you also need to know how long they can be. This is the horizontal distance your stair stringers will occupy. In the project, the stairs go up to a landing, then turn and rise to the next level (an L-shape). The builder measured from the landing edge to the header above and found that:

• Max stair run allowed = 123 inches

Your space may differ, so measure carefully. Obstacles like walls, doors, or headroom constraints can limit your stair length.

4. Step Three: Calculate the Number of Steps

Now you must figure out how many steps it will take to safely and comfortably climb 123 inches.

4.1 The Math

You calculate this by dividing total rise by a possible number of steps until you hit a riser height that fits code.

Let’s test various step counts:

• 123 ÷ 14 = 8.7 in → Too tall (over max)

• 123 ÷ 15 = 8.2 in → Still too tall

• 123 ÷ 16 = 7.68 in → Within code, but high

• 123 ÷ 17 = 7.23 in → Perfect (safe + comfortable)

So the ideal riser height is:

Final Riser Height:

≈ 7¼ inches per step

This height is comfortable for walking and safely under the maximum code limit.

5. Step Four: Determine Your Tread Depth (Run)

The run is how deep the step is (the part you step on).

In this build, the material used was:

• 2×12 lumber

• Actual width: about 11 inches

To achieve a ¾-inch overhang on each tread:

• Cut stair run at 10¼ inches

Why 10¼"?Because:

• 11" board width

• Minus ¾" overhang

• Leaves 10¼" as the cut line for the stringer

If using riser boards (¾ inch thick), they shift the tread out the same amount, so the overhang still ends up correct.

6. Step Five: Adjust the Run if Space Is Tight

If you have limited space between walls or you must fit the stairs into a measured opening, you can adjust the tread depth downward, but never below the minimum allowed by code (commonly 10 inches).

You divide total available floor space by the number of treads to fine-tune your run.

7. Step Six: Check and Calculate Head Clearance

One crucial code requirement is headroom — the distance from the stair slope line to the ceiling above.

Most areas require at least 6 feet 8 inches of clear space.

To calculate it:

1. Place a straight edge from the nose of the bottom tread to the nose of the top tread (the stair slope line).

2. Measure vertically from the ceiling surface (finished) to this line.

In the project example:

• They achieved 6' 8½" to allow for the drywall thickness not yet installed.

8. Step Seven: Calculate the Landing Height

The landing must also meet the step rise system.

The highest allowable landing height (before cutting into headroom) was:

• 34 inches measured from the floor to the underside of the future ceiling minus drywall thickness.

To keep step spacing consistent at 7¼ inches, they solved:

• 7¼ × 4 = 29 inches

Which means the landing must sit 29 inches above the floor, because that ensures four perfectly even risers.

Then:

• Subtract ¾" for future subfloor thickness → mark framing height.

9. Step Eight: Build the Landing

For a landing measuring 42 inches deep, the minimum requirement is generally 36 inches in the direction of travel, so 42 inches was acceptable.

Key requirements when framing the landing:

• Landing must reach back far enough to fully support the bottom of the upper stringer (at least 13 inches).

• Use proper header supports, studs, posts, or joist hangers.

• Transfer load to the foundation or structural members.

• Install subfloor using construction adhesive + nails/screws to eliminate squeaks.

In the example, the landing was framed with:

• Support boards fastened to the side studs

• Vertical blocks transferring weight to the foundation

• A 2×12 header supported on a 6×6 post

10. Step Nine: Install the Ledger Board for the Stringers

A ledger board is mounted under the landing to support the top of the lower stringers. It provides a secure fastening point.

Once installed, the builder double-checked that:

• The bottom-to-ledger height was exactly 29 inches, matching the stair calculations.

11. Step Ten: Lay Out and Cut the First Stringer

This is the most important—and often the most confusing—part of building stairs. But once you cut one good stringer, the rest become simple because you just copy it.

Tools Needed

• Framing square

• Stair gauges

• Sharp pencil

• Circular saw

• Jigsaw

11.1 Crown the Board First

Every 2×12 has a slight curve (crown). Always install stringers with the crown up, so weight pushes it straight.

11.2 Set Stair Gauge Positions

On the framing square:

• Run side: 10¼ inches

• Rise side: 7¼ inches

Tighten the stair gauges so the square can slide along the lumber edge without shifting.

11.3 Marking the First Stringer

Start at the board's end and mark:

• The step rise

• The step run

• Repeat for the number of treads required

Important Adjustment: Bottom Tread

You must remove 1½ inches from the first rise because the bottom tread sits directly on the floor, not on a riser. This prevents the first step from being too tall.

11.4 Cut Carefully

Use a circular saw for straight cuts, but do not over-cut the corners, or the stringer will weaken. Use a jigsaw to finish the cuts cleanly.

12. Step Eleven: Test Fit the First Stringer

Before cutting the rest, always test the layout of your first stringer.

• Temporarily place it against the ledger and floor.

• Mark 8¾ inches down from the landing (7¼ riser + 1½ tread thickness) to check alignment.

• Use a level on each tread area.

If everything matches your measured rise/run system, your template is correct.

If not—fix it now. Cutting all stringers incorrectly would be a huge waste.

13. Step Twelve: Cut Remaining Stringers Using the Template

Once the test stringer fits:

1. Place it on top of a new 2×12.

2. Align both boards perfectly.

3. Clamp both ends tightly.

4. Trace the outline with a sharp pencil.

5. Cut out the remaining stringers.

This guarantees all stringers match perfectly.

14. Step Thirteen: Prepare the Upper Stringers

The second set of stringers (from landing to upper floor) is laid out the same way, except:

• You do not subtract ¾ inch at the top because this section does get a riser installed.

Mark, adjust, cut, and test-fit them exactly as you did the lower set.

15. Step Fourteen: Install All Stringers

After confirming that:

• All stringers match

• All are level

• All support points align

You can install them onto:

• Ledger boards

• Bottom kick plates

• Headers

• Landing edges

Use structural screws, lag bolts, or approved fasteners. Avoid common nails — they are not strong enough for long-term load.

16. Step Fifteen: Add Skirt Boards

Skirt boards are long boards that run along the wall behind the stringers.

Advantages:

• Cleaner finished look

• No need to notch drywall around every tread

• Hide small gaps between wall and stairs

• Easier to caulk and paint

Skirt boards can be ¾-inch or 1½-inch thick. In the example build, thicker boards were used for added strength and appearance.

Attach skirt boards BEFORE installing treads and risers so the stringers sit neatly against them.

17. Step Sixteen: Install Treads and Risers

Once the structure is complete:

1. Begin installing riser boards (¾ inch thick).

2. Install treads (usually 1½ inches thick).

3. Add construction adhesive to reduce squeaks.

4. Secure using finishing nails or screws depending on material.

Maintain:

• Uniform overhang (around ¾ inch)

• Consistent step height from bottom to top

18. Step Seventeen: Final Checks

Before considering the project complete, verify the following:

Step Height Consistency

Measure every riser from the bottom step to the top.Variation should be less than ⅜ inch, but preferably negligible.

Tread Level

Place a level on each one.They must be perfectly level side-to-side and front-to-back.

Head Clearance

Make sure the final measured clearance is at least 6'8".

Landing Stability

Verify that:

• All joists are secured

• Subfloor is properly fastened

• No bounce or movement exists

Stringer Spacing

For residential stairs:

• No more than 16 inches on center

In the example, four stringers were used, giving about 10 inches spacing—extra strong.

Conclusion: DIY Stair Building Is Completely Achievable

Building a set of stairs may seem like a complex project, but when broken down step by step, it’s extremely manageable. The key is to:

• Follow building codes

• Take exact measurements

• Double-check your math

• Cut one perfect stringer before duplicating it

• Support the landing and stringers properly

• Verify level, rise, and headroom

With patience and precision, you can build safe, durable, and professional-quality stairs that will last for decades.