Which term refers to a horizontal wood-framing member used in floor and ceiling constructions?

The term that refers to a horizontal wood-framing member used in floor and ceiling constructions is "joist." Joists are structural elements that support the weight of floors and ceilings, running parallel to one another. They provide a framework for the flooring material, allowing for the distribution of loads across the space.

Joists are essential in creating a strong and stable structure, and they often span between beams or walls. The spacing and size of joists depend on factors like the load they need to carry and the materials being used. In residential construction, timber or engineered wood products are commonly used for joists, ensuring both strength and efficiency.

The other terms mentioned play different roles in construction. Beams are typically larger horizontal members that support loads from joists and carry them to vertical supports. Rafters are inclined framing members used in roofs that support roof sheathing and roofing materials. Purlins are similar to rafters but are usually found in roof systems to provide additional support to the roof sheathing. Each of these components serves a unique purpose, but when it comes specifically to horizontal framing members in floors and ceilings, joists are the correct term.