Excavation and muck-away
Excavation volume: rectangular pit, slab dig or trench
- where
- excavated (bank) volume (m³)
- number of identical digs
- length (m)
- width (m)
- depth (m)
Explain this equation
This gives the solid volume of a straight-sided dig: a footing trench, a drainage trench, a pad pit or a slab reduce-dig. It is the starting point for spoil, muck-away and concrete quantities.
L, W and D are the length, width and depth of one dig, measured from existing ground down to formation. N is how many identical digs there are, such as a row of pad foundations.
A box is length times width times depth, so the volume is simply their product, multiplied by the number of boxes.
Sense check: a 10 m run of 600 mm wide trench, 1 m deep, is 6 m³ in the ground. Double the depth and the volume doubles.
Watch out: this is the in-ground (bank) volume. Once dug it bulks up, so convert it before booking skips or lorries.
Works out the solid (bank) volume of a vertical-sided dig: a strip foundation trench, a drainage trench, a pad pit or a reduced-level slab dig.
Enter your values to see the result.
Good to know
This is the volume as it lies in the ground. Once dug, soil bulks up, so use the bulked-volume calculator before booking skips or lorries. For a strip footing round a building, use the centre-line length of the trench so corners are not counted twice. Measure depth from existing ground to formation level.
Common mistake
Ordering skips from the in-ground volume. Dug clay takes up about a fifth more space than it did in the ground.
Limits
Vertical sides and a level base only. For battered or stepped sides use the battered excavation calculator.
Sources
Results are calculations from the published methods and figures shown, and depend on the data you enter. Follow BS 8500, BS EN 206, BS EN 752, Building Regulations Part H, manufacturers’ data and your engineer’s design. Structural concrete and foundations need a competent designer.