Bulls floats are used when achieving which specific F-number floor flatness?

• A. F-10
• B. F-20
• C. F-30
• D. F-40

Answer: (B)

A bull float is used to bring a plastic concrete surface to a uniform, mid-range plane right after screeding. It smooths ridges and closes the surface enough to be workable, without finishing it to a ultra-smooth state. The F-number scale measures how flat the floor is, with higher numbers meaning flatter surfaces. The bull float stage typically yields a flatness around F-20, which is why this tool is associated with achieving that level. If you aim for rougher finishes (lower flatness), you’d still see ridges or inconsistencies; for very high flatness (F-30 or F-40), you’d continue with finer finishing steps like additional troweling. So the bull float best aligns with reaching F-20 floor flatness.