Estimating the substructure: earthwork, sand filling, soling and lean concrete

The substructure items come first in every BOQ and set the rhythm of the whole estimate.

1. Earthwork in excavation

Measure the pit or trench size including working space — commonly 150–300 mm beyond the footing on each side, more for deep pits — multiplied by depth from existing ground level.

Volume = length × breadth × depth (cum or cft)

Note the soil type and depth band in the description; deep or wet excavation and dewatering are separate items.

2. Sand filling in foundation trenches

Sand (fineness modulus around 0.8–1.2) is filled in layers and compacted under footings and in plinth areas. Measure the compacted volume. If sand is bought loose, allow for compaction: loose volume is roughly 1.2–1.25 × compacted.

3. Brick flat soling

One layer of bricks laid flat over compacted sand, joints filled with sand, measured by area (sqm or sft) under the footings and floors.

4. Lean concrete (CC 1:3:6)

Blinding concrete, usually 75 mm (3") thick, over the soling, measured by volume. It gives a clean, level surface for the footing reinforcement. Material quantities follow the concrete dry-volume method.

5. Polythene sheet

Where specified, a polythene sheet between soling and concrete is measured by area.

6. Then the footing

Reinforcement, formwork and RCC in the footing follow, then the column stumps and grade beams, damp-proof course and plinth filling.

Sequence in EstiMatrix

Add earthwork in excavation and EstiMatrix suggests sand filling, then brick flat soling, then CC 1:3:6, then footing reinforcement and RCC footing — one click each, from the PWD SoR for your zone.

Back-filling

Excavated earth returned around foundations is measured separately (earth filling in plinth or around foundations), and surplus earth carried away if required.