How Far Apart are Spindles/Balusters on a Deck?

When referring to “spindles” on a deck, you’re likely talking about balusters, which are the vertical members used to fill the gap between the handrail and the deck or stair treads. The spacing between these balusters is primarily determined by building codes to ensure safety, especially for children.

In the U.S., the International Residential Code (IRC) stipulates that a 4-inch diameter sphere cannot pass through the spaces between balusters. This is to prevent small children from getting their heads stuck between the balusters. Therefore, the actual space between balusters is often slightly less than 4 inches.

Here’s a simple way to determine the spacing:

  1. Determine Baluster Width: Measure the width of a baluster. Let’s say it’s 1.5 inches.
  2. Determine Maximum Gap: The maximum gap is 4 inches (based on the IRC).
  3. Calculate Combined Width: Add the width of the baluster to the maximum gap. In this example, 1.5 inches + 4 inches = 5.5 inches.
  4. Determine Spacing: Subtract the width of the baluster from the combined width to get the space between each baluster. In this example, 5.5 inches – 1.5 inches = 4 inches.

So, in this example, you’d space the balusters 4 inches apart on center to ensure that the gap between them is less than 4 inches.

Remember, always check with your local building codes and regulations, as they may have additional or different requirements.

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