🇱🇨 Saint Lucia · SMM7 · Work section
Substructure & foundations in a Saint Lucia bill of quantities
In Saint Lucia, the substructure section of a Bill of Quantities (BoQ) is measured to SMM7 — Standard Method of Measurement (Commonwealth practice). It covers 7 principal groups of work — site clearance and removal of topsoil through to ground floor slab and any thickenings — and is headed in the bill as "ELEMENT NO. 03 — SUBSTRUCTURE & FOUNDATIONS".
Substructure & foundations is one of the sections every Bill of Quantities (BoQ) in Saint Lucia is built from. This page sets out what belongs in it, the unit each item is measured in under SMM7 — Standard Method of Measurement (Commonwealth practice), the local conventions that change the quantities here, and a worked example for a 150 m² house — plus the errors in this section that actually cost money on site.
What this section covers
- Site clearance and removal of topsoil
- Excavation to reduce levels and to foundation trenches
- Earthwork support and keeping excavations free of water
- Disposal of excavated material, on site or off
- Mass or reinforced concrete footings
- Hardcore filling, blinding and damp-proof membrane
- Ground floor slab and any thickenings
How each item is measured
| Item | Unit | Measurement rule |
|---|---|---|
| Excavation | m³ | Measured net from existing ground level to the underside of the concrete. Working space is a separate item, not an addition to the volume. |
| Disposal | m³ | Bulk excavated volume, with an allowance for bulking — spoil occupies more once dug than it did in the ground. |
| Concrete in footings | m³ | Measured net; no deduction for reinforcement or for voids under about 0.05 m³. |
| Hardcore filling | m³ or m² | Measured to the compacted thickness. Loose delivered volume is materially greater. |
| Damp-proof membrane | m² | Net area covered; laps and turn-ups are deemed included in the rate. |
| Ground floor slab | m³ or m² | Measured on the net area, stating the thickness. |
Local conventions in Saint Lucia
- —Foundations here are conventionally strip type, taken 0.6 m deep and 400 mm wide.
- —Footing concrete is normally a 1:2:4 mix, with 50 mm blinding beneath and 150 mm of hardcore under the slab.
- —A damp-proof course and membrane are standard practice and must be measured — leaving them out is the most expensive omission in this section.
Worked example — 150 m² house in Saint Lucia
Quantities for this section on a representative single-storey house, computed from Saint Lucia construction conventions. Rates are deliberately not shown: they move constantly and are priced against your own drawings.
| Description | Qty | Unit |
|---|---|---|
Trench excavation 50 m perimeter × 0.4 m wide × 0.6 m deep | 12 | m³ |
Mass concrete footings 225 mm thick strip footing, mix 1:2:4 | 4.5 | m³ |
Hardcore filling 150 mm bed under the ground slab | 22.5 | m³ |
Blinding concrete 50 mm blinding over hardcore | 7.5 | m³ |
Ground floor slab concrete 100 mm slab over 150 m² | 15 | m³ |
Damp-proof course / membrane Slab area plus 10% laps | 165 | m² |
What goes wrong in this section
- —Substructure is the section most often priced from the drawing rather than from the ground. A trial pit that finds soft material below founding level re-prices the whole section.
- —Trench depth and concrete thickness are different numbers. Measuring concrete to the full trench depth over-orders by a third or more.
- —Disposal is routinely forgotten. On a constrained urban site, carting spoil away can cost more than digging it.
Get every section measured, not just this one
Upload your dimensioned drawings and get a complete bill of quantities (boq) in the SMM7 format, priced in XCD ($), with every rate source-cited.
Generate my Saint Lucia BoQSubstructure & foundations — frequently asked
What goes into the substructure section of a bill of quantities in Saint Lucia?
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Site clearance and removal of topsoil; Excavation to reduce levels and to foundation trenches; Earthwork support and keeping excavations free of water; Disposal of excavated material, on site or off; and 3 further groups of work. Under SMM7 each is described, measured in its own unit, and priced separately so the total is auditable line by line.
What units is substructure & foundations measured in?
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Excavation in m³, Disposal in m³, Concrete in footings in m³, Hardcore filling in m³ or m². Getting the unit right matters more than getting the quantity precisely right — a contractor can adjust a quantity, but cannot price an item measured in the wrong unit at all.
How is substructure & foundations different in Saint Lucia from elsewhere?
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Foundations here are conventionally strip type, taken 0.6 m deep and 400 mm wide.
What is the most common costly mistake in this section?
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Substructure is the section most often priced from the drawing rather than from the ground. A trial pit that finds soft material below founding level re-prices the whole section.
How do I get this section measured for my own project?
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Upload your dimensioned drawings to Enormous Buildings. The bill is produced in the SMM7 format, grouped by section with substructure & foundations priced in XCD ($), and every unit rate carries a source so a Saint Lucia quantity surveyor can check it.