Category: Structure & materials
Prepared by Eng. Ahmed Fathy, Projects Manager ·
Definition
Excavation removes soil down to the foundation level set by the structural drawings and soil report, either bulk excavation for a basement or local excavation for footings and ground beams, with the spoil carted away or stockpiled for backfill.
Why it matters on a project
Excavations deeper than 1.2 m need safe slopes or shoring depending on the soil. Soil type, sand or rock, changes cost and time a great deal.
Measurement and pricing
In cubic metres from the levels on the drawings, with rock measured separately, and cart away in cubic metres after the bulking factor.
Worked example
A 20 x 15 m basement dug 3.5 m deep: 20 × 15 × 3.5 = 1,050 m³, and with a bulking factor of 1.25 the cart-away volume is 1,050 × 1.25 = 1,312.5 m³.
Common mistake
Pricing cart away on the in-situ volume without the bulking factor, so actual truck trips exceed the estimate.
Frequently asked questions
When does an excavation need shoring?
When it is deeper than about 1.2 m and safe slopes are not possible, or next to existing buildings or roads.
Is excavation in rock more expensive?
Clearly yes, it needs breakers and more time, so it is priced as a separate item.
Related terms
- BackfillRefilling excavations around foundations with suitable soil in compacted layers.
- Soil investigation reportThe borehole study on which the foundations are designed.
- DewateringLowering groundwater so excavation and foundations can be built dry.
- Compaction testA test proving backfill layers are compacted to the required density.
Read next
- Quantity Takeoff for Contractors, Step by Step
- Work out quantities with our free calculators: concrete, tiles, paint and plaster. Open the calculators
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