What should cover the space between adjacent treads in deck stairs?

The correct answer, which specifies using a 4-inch diameter sphere to cover the space between adjacent treads in deck stairs, stems from the safety and code compliance aspects associated with stair design. This measurement is intended to prevent small children from slipping through the gaps that could exist between treads, which could lead to dangerous falls.

Using a 4-inch diameter sphere ensures that the openings between the treads are not large enough for a child to pass through, thereby promoting safety in residential and commercial settings. Building codes often stipulate these measurements to help maintain uniformity in stair design, ensuring that all structures provide a certain level of safety for users.

This standard of using a 4-inch diameter sphere helps ensure that the gaps are neither excessively large nor small, adhering to safety regulations while considering practical use in everyday scenarios.