When should wet screeds be used?

Wet screeds are typically used when the concrete is still in a plastic state, which aligns with the option that specifies the condition under which wet screeds are appropriate. Using wet screeds helps to ensure a smoother finish and better consolidation of the concrete when finished properly.

The Floor Flatness (FF) number metric helps measure the flatness of a concrete surface, and values above 20 indicate a higher flatness requirement. When higher FF numbers are specified, employing a wet screed is advantageous as it assists in achieving a flatter and more level surface as excess moisture in the mix allows for more workable material, which can contribute to the desired finish.

Other scenarios, such as ambient temperatures exceeding 80°F or slab thicknesses less than 4 inches, are considerations that do not necessarily dictate the use of wet screeds. Instead, they may influence drying times or finishing techniques but do not align as closely with the designated conditions for optimal use of wet screeds, thereby rendering them less relevant to this specific context.