A carpenter is setting grade stakes for a concrete slab pour that is 150 mm thick, and the finished floor elevation is 22.150 m. The benchmark is at 20.000 m. If the top of the grade stake is 22.000 m (elevation), what instruction should be written on the stake for the concrete finisher?

Question: A carpenter is setting grade stakes for a concrete slab pour that is 150 mm thick, and the finished floor elevation is 22.150 m. The benchmark is at 20.000 m. If the top of the grade stake is 22.000 m (elevation), what instruction should be written on the stake for the concrete finisher?

Answer options:

• ADD 150 mm ✅ FILL 150 mm
• Cut 150 mm
• ADD 300 mm

Correct answer: FILL 150 mm

Explanation: The desired slab soffit elevation is 22.150 m - 0.150 m = 22.000 m. Since the top of the stake is at 22.000 m, and this is the slab soffit elevation, no direct cut/fill for sub-grade preparation is needed. However, if the stake was meant to be for the finished concrete surface, and the stake top is at slab soffit, then 150 mm of fill (concrete) is needed to reach the finished grade. The question implies the instruction for the finisher to reach slab top: 22.150 (F.F.L.) - 22.000 (stake top) = 0.150 m = 150 mm of concrete on top of the stake. So a common instruction would be 'FILL 150 mm' indicating the thickness of concrete above that subgrade point (stake top).