Is There a Minimum Standard for Deck Railing Slats?

Standard Railing Slats

• Deck railing slats are the vertical posts that fill the space between the handrail and the bottom horizontal timber of the railing. The slats can be custom designed or purchased in standard sizes as part of a deck railing system. The size depends on the style of the railing and the deck design, and can vary from a delicate 1 1/2-inch-diameter spindle to a wide plank of 5 inches. The styles, sizes and available finishes of deck railing slats vary greatly.

Railing Standards

• The standard followed by most local building codes in the U.S. requires deck and porch railing slats to be close enough together that a 4-inch sphere cannot fit between the slats. However, it is not enough to know about this standard. When building a deck railing, it is important to verify local building code requirements and inquire about obtaining a building permit. Most U.S. cities require a building permit before beginning construction on a remodeling project or an addition, which may include a new or replacement deck. To be sure you are within the safety standard, you may wish to plan 3 1/2-inch openings between your slats.

Verify Building Code

• Cities use a building code, permit process and follow up inspections to ensure a structure meets safety standards. A city or county building and permit department manages the process. Contact the building department for details about deck railing requirements and permits, or visit the department's website to find the information. In areas where a permit is not needed, the four-inch standard should be followed. When a permit is required to build a deck, the lack of a permit can trigger a fine and a demand from the city or county to end construction.

Other Deck Railing Standards

• The four-inch standard applies to the space between the railing slats as well as the space between the deck floor and the lower, horizontal timber that holds the slats in place. The rule is in place to reduce the chances a pet or person, especially a small child, could push his head or body through the railing system and fall or become stuck. Additional requirements found in most building codes require any deck or similar structure, such as a porch, sitting 30 inches or higher above the ground to include a railing system. Railings are usually required to be between 36 and 44 inches high, depending upon the location and the type of structure. Building codes also include requirements for stairs and stair railings for porches and decks.