Groundworks Programme: How Long Should a Commercial Groundworks Package Take?

For project managers, contracts managers, and commercial teams, the groundworks programme is often the critical path on a construction schedule. The duration of this phase determines when the superstructure starts, when follow-on trades mobilise, and ultimately when the project completes.

But groundworks programmes are notoriously difficult to estimate with precision. The same foundation package on two different sites can take weeks longer on one than the other, driven entirely by ground conditions, access constraints, or design coordination issues that were not apparent at tender stage.

This article breaks down the typical phases of a groundworks programme, what drives the duration of each, and what procurement teams can do to build realistic programmes that account for the variables. For package scope context, see Planning a Groundworks Package for a Commercial Development.

Every commercial groundworks package follows a broadly similar sequence, though the weight and duration of each phase varies significantly by project type, scale, and site conditions.

Mobilisation is often the phase most underestimated in programme planning. It includes delivering plant to site, setting up site accommodation, installing welfare facilities, and establishing site access — often overlapping with enabling works.

What drives the duration:

• Distance from the contractor’s plant yard to site
• Access constraints affecting delivery routes
• Scale of welfare and site accommodation required
• Time required to install haul roads or working platforms before plant can move

Mobilisation also includes pre-start compliance activities. Method statements for excavation, subgrade preparation, and drainage must be submitted and approved before work can commence. These approvals have lead times that are not entirely within the contractor’s control.

Realistic expectation. Even on a straightforward project, mobilisation and site setup cannot be compressed into a single day. On larger phased developments, mobilisation might run in parallel with ongoing enabling works, with the groundworks contractor mobilising into one zone while enabling works complete in another.

Earthworks establish the formation levels and platforms for the building and site infrastructure. This phase includes reduced-level excavation, cut and fill operations, and subgrade preparation — core excavation contractor activity on many commercial packages.

What drives the duration:

• Volume of material to be moved — calculated from topographical survey and design levels. The volume “in the ground” differs from the volume “as dug” (swell factor), which affects haulage volumes.
• Ground conditions — excavating through rock or waterlogged clay takes longer than dry, stable ground.
• Plant availability and access — the number of excavators and dumpers the site can accommodate affects the rate of material movement.
• Spreading and compaction — where material is reused on site, compaction testing is required, which adds time and requires weather windows.

Earthworks programmes should be based on achievable production rates for the specific ground conditions. Survey accuracy matters too — variations in ground levels found during excavation are a common cause of extended programmes.

Drainage is often the most complex and programme-critical element of a groundworks package. Deep drainage runs are typically the first permanent works to go in, and they must be completed before foundations can proceed across large areas of the site. See commercial drainage.

What drives the duration:

• Depth of drainage runs — deeper trenches take longer to excavate and require more careful shoring and dewatering.
• Ground conditions — waterlogged ground requires pumping; rock requires breaking; unstable ground requires trench support systems.
• Complexity of the network — the number of manholes, changes of direction, and connections to existing systems.
• Testing requirements — air or water tests before backfilling are hold points until the inspector signs off.
• Phasing — on large sites, drainage is often installed in phases, with each phase requiring connection to the existing system.

What this means in practice. Drainage generally cannot be completed while other works are underway in the same area. It needs a clear run. If the drainage layout changes after installation begins, the programme impact is immediate and significant.

Foundations form the permanent substructure. This phase typically includes excavation to foundation level, concrete blinding, reinforcement installation, and concrete pouring. Method choice sits with foundation contractors and, where relevant, piled solutions.

What drives the duration:

• Foundation type — strip or trench-fill foundations are relatively fast. Piled foundations need specialist plant. Rafts involve significant reinforcement and concrete volumes.
• Number and size of foundations — multiple column pads and lift pits take longer than a residential strip package.
• Inspection hold points — reinforcement must be inspected and signed off before concrete is poured.
• Concrete logistics — if concrete cannot be delivered on time, the team stands idle.
• Weather — concrete pours can be affected by rain or freezing conditions.

Phasing considerations: on larger schemes, foundations are often sequenced in phases. The groundworks contractor completes foundations in one area while drainage or earthworks continue in another. This introduces interface risk — if drainage in Phase 2 is delayed, the foundations team either sits idle or moves to another area.

Once foundations are complete and the superstructure has progressed, the groundworks contractor typically returns to complete the site-wide external works.

• Area of hardstanding, paving, and roads
• Depths of sub-base and binder courses (determined by design loads)
• Phasing — external works are often sequenced to avoid conflict with other trades, especially around scaffold and delivery routes
• Coordination with services — utility connections to plots or building entrances need coordinating with the groundworks programme

Adoption requirements. If roads and sewers are to be adopted, additional inspection and testing apply. Section 38 or Section 104 processes run on a schedule defined by the adopting authority, not the contractor — and must be factored into the programme.

The final phase involves site clearance, final inspections, and handover documentation. QA sign-off from the structural engineer, Building Control, and any adopting authorities is required before the site can be signed off.

• Inspection availability — if the inspector is not available to sign off, the programme is delayed
• Testing and validation — retaining walls, drainage systems, and pavement construction require specific tests and records
• Rectification of defects — issues identified during inspection must be corrected before handover

Groundworks programme slippage typically comes from one of several sources. Understanding these helps procurement teams build realistic programmes and assess the risks.

Ground conditions drive programme duration. If ground conditions prove more difficult than anticipated—waterlogged ground, rock, contaminated material—the programme extends immediately. Without proper investigation before tender, the programme is built on assumptions. See ground investigation services.

If the groundworks contractor does not receive complete drawings, drainage design, or structural information before mobilising, the programme is compromised. Late design changes are a common cause of delay. On housing schemes, if drainage invert levels or foundation details change after excavation has started, rework is required. Use the groundworks tender checklist before going to market.

If plant or materials cannot access the site as expected, the programme is delayed. Access constraints—narrow lanes, weight limits, limited turning areas—extend haulage times and reduce production rates.

Groundworks are weather-sensitive. Excavation, drainage installation, and concrete pours are all affected by rain, frost, and excessive heat. A wet winter can add weeks to a groundworks programme. Realistic programmes allow for weather downtime.

Service diversions, planning condition discharge, and Section 38 or 104 approvals have lead times that are not within the contractor’s control. If utility diversion is on the critical path, the programme is at the mercy of the utility provider’s schedule.

A recent TCC case (Grain Communications v Shepherd Groundworks [2024]) highlighted the commercial risks of programme uncertainty — the court allowed postponement of works indefinitely where the contract had a broad variation clause.

On projects where enabling works and groundworks are procured separately, the handover between packages is a programme pinch point. If enabling works overrun or the site is not left in the condition the groundworks contractor expected, the programme is impacted immediately. See Enabling Works Before Construction.

Plant breakdown is a manageable risk if the contractor has access to backup plant. Labour availability, particularly for specialist groundworkers with plant operator cards, is a constraint on some projects. If the contractor cannot resource the programme, it slips.

The quality of the tender information directly determines the programme’s reliability. A contractor cannot programme accurately without:

On larger developments, groundworks are often phased. This reduces the overall programme duration by allowing the contractor to move from one zone to the next.

For a housing development, for example:

• Enabling works in Phase 1 complete
• Groundworks start in Phase 1 (drainage, foundations, plots)
• Phase 2 enabling works run in parallel
• Groundworks move to Phase 2
• Phase 1 roads and external works run as plots are completed

This phased approach is efficient but introduces interface risk. If Phase 2 enabling works are delayed, the groundworks team sits idle or relocates, and both options cost money.

Where phasing is planned, the interface between phases must be managed. The contractor needs to know the phase boundaries, the sequence, and the handover conditions for each zone.

Programme duration has a direct commercial impact — also reflected in the drivers covered in Groundworks Cost Breakdown:

• Preliminaries — site accommodation, welfare, and site management are time-related costs
• Plant hire — plant is often hired by the week; programme extensions add hire costs
• Overheads — the contractor’s overhead recovery is based on programme duration
• Liquidated damages — delayed completion exposes the contractor to LADs, which they will price into the tender if the programme is unrealistic

For procurement professionals, realistic groundworks programmes are built on complete information and a clear understanding of the variables. Incomplete ground investigation, unclear drainage design, and optimistic assumptions about access and weather are the main causes of programme slippage. The time invested in preparing a complete tender package with accurate programme constraints pays back when the groundworks package completes on schedule and the superstructure phase begins as planned.

If you are planning a groundworks package and need commercial input on programme and sequencing, Mainline Groundworks can review the available information and discuss how the programme should be structured to manage risk and meet project milestones. Contact the team to talk it through.