Before You Start

A few quick things to know before laying out your railing:

• Use 25" balusters for a 36" rail

• Use 31" balusters for a 42" rail

• Installation is simple: screw down the bases, snap in the balusters, and lock the collars

• Use a variable-speed driver at low to medium torque

• Do not use an impact driver to install the connectors

• Keep stain, paint, solvents, and other chemicals away from the polycarbonate connectors

• The level-rail measurements below do not apply to stairs — stair spacing is covered later in this guide

Standard 4', 6' and 8' Railing Spans

For standard level railing sections, Snap’n Lock Round Balusters are laid out at 4-1/2" on center.

That leaves approximately 3-3/4" of clear space between balusters.

The span is measured as the clear opening between your posts, which is also the length your rail should be cut to.

For these common spans, the Snap’n Lock installation template makes layout fast and simple.

How the Baluster Count Works

The standard layout starts at the center of the rail and works outward.

For an even number of balusters, such as 10 or 16, there is no baluster directly on the center line. Instead, the first marks are positioned 2-1/4" on either side of center.

For an odd number, such as 21 balusters on an 8' section, one baluster sits directly on the center line.

From there, continue marking every 4-1/2" on center until the rail is filled.

The goal is to keep the opening between the final baluster and each post at 4" or less.

Want More Even Gaps at the Posts?

Centering the layout works well, but on longer spans it can leave a smaller gap between the outside balusters and the posts.

For example:

• A 6' rail has approximately 1-7/8" between the post and first baluster

  
  

• An 8' rail has approximately 2-5/8"

  
  

• The gaps between the balusters themselves remain approximately 3-3/4"

If you prefer a more evenly spaced appearance, you can spread the same number of balusters evenly across the full span.

Use this formula:

Spacing on center = (span in inches + 0.75) ÷ (number of balusters + 1)

The number of balusters stays the same, but the gaps at the posts become more visually balanced.

Because the resulting spacing will usually be slightly less than 4-1/2" on center, the standard Snap’n Lock template will no longer match. Instead, measure from one post using a tape measure or spacer block.

How Many Balusters Do I Need for a Custom Span?

If your railing falls somewhere between the standard 4', 6', or 8' sizes, you can calculate the required number of balusters with this formula:

Balusters = (clear span in inches - 4.25) ÷ 4.5

Then round the answer up to the next whole baluster.

Example: 5' 3" Railing Section

A 5' 3" clear opening is 63 inches.

(63 - 4.25) ÷ 4.5 = 13.06

Round up, and you will need:

14 balusters

Always measure the clear opening between the inside faces of the posts.

If you measured from post center to post center instead, subtract the width of the posts first:

• 3-1/2" for a nominal 4x4

• 5-1/2" for a nominal 6x6

What About Stairs?

Stair railings use a different layout.

Snap’n Lock stair installations use 25" balusters with stair adapters, and the rail is marked every 5-1/2" on center.

One important difference: that measurement is taken along the slope of the stair rail, not horizontally.

The installation guide shows a minimum rail height of 34", but always confirm the requirements in your local building code.

To calculate the baluster count for a stair rail, use:

Balusters = (sloped rail length in inches - 4.75) ÷ 5.5

Then round up to the next whole number.

Example: 10' Stair Rail

A 10' sloped railing section measures 120 inches.

(120 - 4.75) ÷ 5.5 = 20.95

Round up, and you will need:

21 balusters

The opening between the post and first baluster should remain no larger than the approximately 4-3/4" gap between the stair balusters.

Always confirm allowable stair openings with your local building authority before installation.