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Most building codes require that railing spindles (also known as balusters) on decks or stairs be spaced no more than four inches apart. This safety standard is often called the '4-inch sphere rule,' which means a sphere with a 4-inch diameter should not be able to pass through the opening between balusters. This rule is in place to prevent small children and pets from slipping through the railing. For the same reason, the space between the bottom rail and the deck or floor surface should also be no more than four inches. As a general guideline, professionals often install three balusters per foot of railing. However, since specific requirements can vary by location, it is essential to check your local building codes to ensure compliance before starting your project.

The proper and most comfortable height for a deck stair riser, also called a step, is between four and seven inches. A height of seven inches is often considered ideal for a strain-free step that minimizes the risk of trips and falls. While it is possible to have risers up to 12 inches, this height can be challenging for children, pets, or individuals with mobility issues. For optimal safety and comfort, pair a seven-inch riser with a tread depth (or run) of at least 10 to 12 inches. Always check your local building codes, as they may have specific requirements that differ from these general recommendations.

You typically don’t need a railing and handrails on a deck that’s less than 30 inches from the ground. However, consider adding them regardless. Railings provide additional safety for you and your guests who use your deck—plus, railings give the deck a more finished look than it would have without them.

Deck stairs should have at least three stringers rather than two. The recommended minimum width for stairs is 36 inches, and the International Association of Certified Home Inspectors recommends at least three cut stringers to provide sufficient support on wood decking stairs of this width. Generally, stringers should be a maximum of 16 inches apart for wood decking and 12 inches apart for more flexible composite decking.