Spindles on a deck may also be called balusters or pickets. While not as important to the structural support of the deck as the rail posts, they play a critical role in ensuring the deck is safe to use by closing in large gaps in the railing. For this reason, balusters must be no more than 4 inches away from one another.

Most building codes require that spindles or balusters on deck and stair railings be spaced no more than four inches apart. This safety standard, often called the '4-inch sphere rule,' is designed to prevent small children or pets from slipping through the railing. A good way to visualize this is that a 4-inch sphere should not be able to pass between two spindles. For the same safety reason, the space between the bottom rail and the deck floor 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 crucial to check your local building codes to ensure compliance before starting your project.

Composite decking requires a solid foundation or substructure for support. This base is typically a frame composed of posts, beams, joists, and footings. The frame can be built from various materials, such as composite, plastic, timber, or metal, depending on your budget, deck type, and environmental conditions. For maximum stability, a professional deck builder may recommend installing this frame on top of a solid concrete base. It is best to discuss the most suitable substructure design and materials for your specific project with a professional.

A deck that isn’t attached to a house is called a floating or freestanding deck. These standalone decks are built near ground level, so they usually don’t need deck stairs. Some don’t even require permits. Generally speaking, building a floating deck is faster and more DIY-friendly than constructing one that’s connected to your home.