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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.

Footings for ground-level decks need to be at least 12 inches deep, and some areas require them to be even deeper. A standard range for deck footings is anywhere from 12 to 48 inches. The minimum footing depth is determined by an area’s frost line and soil conditions. If you’re unsure how deep to install deck footings, check local building codes to find the minimum footing depth in your area. 

Building codes for deck railings can vary by location, so it's important to consult your local regulations before construction. Generally, a guardrail is required for any deck that is more than 30 inches above the ground.

For residential properties, the standard minimum height for a deck railing is 36 inches. However, some states and municipalities have stricter requirements; for example, California and Washington mandate railings that are at least 42 inches high. Therefore, a 42-inch railing is not considered too high and may be required in your area or chosen voluntarily for additional safety.

In addition to height requirements, codes also specify other safety features, such as the maximum spacing between balusters to ensure they are close enough to prevent a child from squeezing through.

In most cases, there should be a small gap between the house and the deck, usually no more than ½ to ¾ of an inch. This space allows water and moisture to flow through instead of pooling against the side of your house. It also lets flashing protect your siding from runoff, which is one of the most common issues with decks.