How much does it cost to build?

A granular sub-base is a dense-graded crushed-rock layer laid onto a prepared formation and compacted in layers to form the load-bearing foundation beneath paving, slabs or a bound surface. In the UK this material is often referred to as Type 1. This rate is the supply, placement and compaction of that granular layer only, measured per m³ of compacted material in place. The material grade is the choice that moves the rate most:

1. Recycled aggregate — crushed concrete or rubble graded to a Type 1 / dense-graded grading; the cheapest option, subject to grading and acceptance
2. Virgin aggregate — primary crushed limestone or granite to UK Clause 803; the standard specification

The rate assumes a trimmed, prepared formation is already in place. Excavation to formation, disposal of arisings, any separation membrane and the surfacing above are all separate activities and are excluded.

Net rate per m³ placed & compacted, national average, excluding overhead and profit. Within each band the low end is a large machine-laid open area and the high end is small or hand-laid work. Assumes ~2.1 t/m³ compacted with a 5% overfill allowance.

Budget rate generator — choose the material grade and how it is placed

• Excavation to formation level
• Disposal and haulage of excavated material (arisings)
• Capping layer beneath the sub-base
• Formation / subgrade trimming, regulating and proof-rolling
• Lime or cement stabilisation of the subgrade
• Geotextile separation or stabilisation membrane
• Compaction testing — CBR, plate-load or nuclear-density-gauge
• Sub-base regulating / blinding to surfacing tolerance
• Edgings, kerbs and channels to contain the layer
• Prime coat to the finished sub-base
• Surfacing — bound courses, slabs or block paving above
• Very small quantities under ~10 m³ — minimum loads and gang call-out push the per-m³ cost above this calculator's range
• Heavy-duty / high-CBR specifications requiring additional compaction passes or thicker construction
• Contaminated or unsuitable material assessment and specialist disposal
• Setting out and survey
• Night, weekend or phased-working premiums
• Road-opening permits and licences
• Traffic management and temporary works
• Preliminaries, overhead and profit
• VAT

Blockwork is the building of walls from precast concrete blocks bedded in mortar — the workhorse walling material for commercial and industrial structures. This is the main-contractor budget rate to supply and lay one m² of single-skin wall — the trade’s cost plus subcontractor and main-contractor overhead & profit. It depends mostly on the block:

1. 100mm lightweight — partition and inner-leaf blocks, cheap and quick to lay
2. 140mm standard — medium-dense load-bearing aggregate blocks
3. 215mm dense — heavy blocks for solid, load-bearing and party walls

The rate covers blocks, mortar, the laying gang, site supervision and overhead & profit. DPC, lintels, wall ties, cavity insulation, any applied finish, scaffold, lifting equipment (provided by the main contractor) and preliminaries are measured separately.

Main-contractor budget rate per m² of wall, supply and lay, national average, including subcontractor and main-contractor overhead & profit but excluding preliminaries, lifting equipment (main contractor), scaffold and VAT. Within each band the low end is a simple wall and the high end is complex detailing. London & SE typically adds 15–25% on labour and supervision.

Budget rate generator

• Damp-proof courses (DPC) and cavity trays
• Lintels and padstones over openings
• Cavity wall ties and partial-fill insulation
• Cavity fill / full-fill insulation
• Movement joints and sealants
• Bed-joint reinforcement beyond the sundry allowance
• Fair-faced or painted finish and separate pointing
• Plastering, rendering or dry-lining
• Scaffold supply (usually in preliminaries)
• Lifting equipment — telehandler / forklift and hoist (provided by the main contractor)
• Very small quantities — minimum delivery loads and mobilisation can dominate the rate
• Preliminaries — main-contractor site set-up, management & welfare
• VAT