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How to Install Stair Balusters

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Updating your staircase by replacing the balusters is one of the fastest ways to transform the look of your home, often without needing to rebuild the entire railing system. Whether you’re modernizing an outdated design or mixing wood and iron for a fresh, custom look, knowing what to expect ahead of time will make your project smoother, safer, and more enjoyable.

A baluster is the vertical post installed between the stair tread (or floor) and the handrail. Balusters come in a variety of materials, most commonly wood and  iron, and a wide range of shapes and profiles. This guide will walk you through both installation methods so you can tackle your stair remodel with confidence.

Before you get started, here are the tools and supplies you’ll typically need:

Tools & Materials Checklist

  • Measuring tape

  • Level

  • Pencil or marking tool

  • Chop saw (metal-cutting blade for iron)

  • Drill and bits

  • Wood glue or construction adhesive

  • Epoxy (for iron balusters)

  • Baluster shoes (optional but recommended for iron)

  • Safety glasses and gloves

  • Finish nails and wood putty (for wood balusters)

  • Vacuum or brush for cleanup

  • Hammer

  • 3M Blue Painter's Tape

With the right preparation, installing new balusters becomes a straightforward and rewarding upgrade. Let’s walk through the essentials.

What Is a Baluster on Stairs?

As mentioned before, a baluster is the vertical post that supports the handrail of a staircase. Sometimes called a spindle, it is the vertical post that runs between your stair tread and handrail. 

The  tread is the horizontal part of the stair you step on, and balusters rise up from each tread (or from the floor on a landing) to help support and secure the handrail. Balusters help form the guardrail system and are required for safety, preventing falls through the side of the stairs or landing. They also play a major role in the aesthetic of your staircase.

How Far Apart Should Balusters Be?

Baluster spacing is essential for both safety and appearance.

Building codes across the U.S. generally require that a 4-inch sphere cannot pass through any opening in a stair railing system.

This means:

  • On straight runs, balusters are usually spaced 3 7/8 inches or less apart.

  • Most staircases use two balusters per tread for balusters that are 1.75” wide and 3 per tread for 1.25” wood balusters & iron.

  • Some designs use three per tread (common with more open risers or modern layouts)

  • Spacing is measured between balusters, not including decorative features on the baluster itself

Always check your local building codes, but the 4-inch rule is the industry standard for safe spacing.

How Many Balusters Do I Need?

To estimate the number you’ll need:

  1. Measure the tread depth (total run of your handrail in inches) and count each step.

  2. Plan for2–3 balusters per step, depending on style and required spacing.

  3. For landings or balcony rails, divide the length of the rail (in inches) by 4 inches to find the maximum spacing allowed.

  4. Round up to the next whole number.

  5. Add a small buffer for cuts, mistakes, or pattern matching.

Here’s a simple way to estimate:

For stair treads

  • Standard layout = 2 balusters per tread, see note above

  • For more intricate patterns = 3 per tread

  • Example: 12 treads × 2 balusters = 24 balusters

For balcony or landing railings

  1. Measure the railing distance in inches.

  2. Divide by 4 inches (maximum opening).

  3. Add 1 baluster to account for the starting point.

Example:
A 96-inch balcony > 96 ÷ 4 = 24 balusters > Add 1 > 25 total balusters

If your design uses patterns, such as two or three balusters per tread, calculate for each step individually.

If you need help calculating your exact quantity,just ask!

Installing Stair Balusters

Below you’ll find step-by-step instructions for installing both wood balusters and iron balusters. Installation varies slightly depending on the material and mounting method.

Installing Wood Balusters

Wood balusters remain a timeless choice for traditional and craftsman-style homes. They typically mount using a dowel pin at the bottom and a tenon or pin top that fits into the rail.

1. Prepare the Handrail and Treads/Trim

  • Ensure the handrail is secure and properly aligned.

  • Mark the locations where each baluster will be installed, following your spacing plan.

  • If your stair uses a plow rail, ensure fillet pieces are removed.

2. Trim the Balusters

  • Measure from tread to rail.

  • Add the depth of the dowel or any fitting you’re using.

  • Cut the baluster to length.

3. Drill the Holes

  • On the tread or baseboard, drill a hole sized for the dowel at each baluster location.

  • Ensure holes are centered and vertical.

4. Install the Balusters

  • Apply wood glue to the dowel.

  • Insert the bottom dowel into the tread hole.

  • Pivot the top of the baluster into the rail plow or against the underside of the rail, depending on your system.

  • Secure with finish nails (if applicable) and reinstall fillet pieces between balusters.

5. Finish the Installation

  • Check alignment and spacing.

  • Sand any rough edges.

  • Stain or paint as desired.

Installing Iron Balusters

Iron balusters are popular for their durability and modern or decorative styling. They typically use shoes (also called bases) and connect with epoxy or set screws.

1. Plan Your Layout

  • Mark baluster positions on the tread/landing.

  • Dry-fit balusters if using patterns (e.g., twist + single basket + double basket).

2. Trim the Balusters

  • Measure from tread to rail.

  • Subtract the height of any shoes being used.

  • Cut the baluster using a hacksaw or metal‑cutting blade.

3. Drill Plumb Holes

  • Drill holes in the underside of the handrail (or use existing holes if replacing).

  • Drill matching holes on the tread or base.

4. Install the Shoes

  • Slide the shoe onto the baluster before setting it in place.

  • Do not tighten yet.

5. Install the Baluster

  • Insert the top of the baluster into the rail hole first.

  • Lower the baluster into the base hole.

  • Apply epoxy in the upper hole (if required).

  • Ensure it is perfectly plumb.

6. Secure the Shoes

  • Once plumb and set, tighten the shoe’s set screws.

  • Check spacing and alignment.

For a wide selection of iron styles, finishes, and coordinating railing parts, explore the full collection  here.  

Choosing the Right Balusters

Whether you're leaning toward the warm, traditional feel of wood or the bold, modern look of iron, the right balusters can completely redefine your staircase. For a full selection of styles, patterns, and materials, explore:

Explore all options in the full  baluster collection.

Final Tips for a Successful Installation

  • Always verify compliance with local building codes.

  • Use a level frequently to ensure balusters stand perfectly vertical.

  • Pre-finish wood balusters before installation for a cleaner result.

  • When mixing wood and iron, ensure spacing and patterns remain visually balanced.

If you need help choosing the right balusters or compatible stair parts, the experts at Stair Parts USA can help you find exactly what you need.