An excavator is digging a trench for a footing. The grade stake indicates 'Top of Footing 101.500 m FFE'. The FFE (Finished Floor Elevation) is set at 102.200 m. The footing is to be 0.400 m thick, and the concrete slab is 0.100 m thick, resting on top of the footing. What is the required depth of excavation from the actual ground elevation of 102.000 m, to the bottom of the footing?

Question: An excavator is digging a trench for a footing. The grade stake indicates 'Top of Footing 101.500 m FFE'. The FFE (Finished Floor Elevation) is set at 102.200 m. The footing is to be 0.400 m thick, and the concrete slab is 0.100 m thick, resting on top of the footing. What is the required depth of excavation from the actual ground elevation of 102.000 m, to the bottom of the footing?

Answer options: ✅ 1.000 m

• 0.900 m
• 0.700 m
• 1.100 m

Correct answer: 1.000 m

Explanation: The wording 'Top of Footing 101.500 m FFE' is ambiguous. Assuming 'Top of Footing' is the target elevation and FFE is just a reference. Let's re-evaluate based on common construction practices: If the FFE is 102.200 m, and the slab is 0.100 m thick, the top of the slab is the FFE. Assuming the footing is below the slab, and the 101.500 m stake is the bottom of the footing for excavation purposes. If Top of Footing is 101.500m, and the footing is 0.400m thick, then the Bottom of Footing is 101.500m - 0.400m = 101.100m. The current ground is 102.000m. So, excavation depth = 102.000m (Ground) - 101.100m (Bottom of Footing) = 0.900m. This makes more sense.