5 Preliminaries Mistakes That Quietly Inflate Nigerian Building Budgets

Preliminaries mistakes are rarely dramatic — no single event, just a series of small underestimates that compound quietly across a project's full duration until the gap between budgeted and actual cost becomes obvious only at completion. This guide covers five common mistakes, using the framework behind our free Preliminaries Calculator.

Mistake 1: Ignoring the Relationship Between Duration and Cost

Budgeting preliminaries as a single fixed figure without explicitly tying it to a realistic project duration is the root cause behind most preliminaries overruns. When the project inevitably takes longer than the optimistic original schedule — a near-universal experience in construction — duration-linked preliminaries costs (site management, facility hire) rise with it, but the original fixed budget line does not automatically adjust to reflect this, quietly eating into project profitability or client contingency.

Mistake 2: Underinvesting in Site Security

Site security guard costs are sometimes trimmed to save money, particularly once a project appears to be progressing smoothly with no incidents — but this is precisely the point at which complacency creates risk. Material theft from an unsecured or under-secured site, particularly of high-value items like cement, steel and fittings once they arrive on site, can represent a real and entirely avoidable cost that dwarfs the modest saving from reduced security presence.

Mistake 3: Combining Preliminaries and Mobilisation Without a Clear Boundary

Where a project's costing does not clearly distinguish preliminaries from mobilisation, it becomes easy to either double-count certain items across both sections or, in the opposite failure mode, to assume an item is covered by the other section when it is not budgeted anywhere at all. Establish a clear, explicit boundary between the two — even if using a single combined heading in the final BOQ — so nothing falls into the gap between them.

Mistake 4: Not Planning for End-of-Project Costs Early

Waste removal, final site clean-up and demobilising remaining personnel are costs incurred at the very end of a project, and are easy to deprioritise in early budgeting when the focus is naturally on getting construction started. By the time these end-of-project costs are due, project funds are often already stretched from cost overruns elsewhere, making a previously "minor" line item a genuine problem to fund at exactly the wrong moment.

Mistake 5: Treating Safety Compliance as a Box-Ticking Exercise

Safety induction, permit holder registration and ongoing compliance documentation are sometimes budgeted at the bare legal minimum, or worse, only partially implemented in practice even where budgeted, treating them as a formality rather than a genuine risk-reduction investment. Beyond the direct human cost of an accident, an under-resourced safety programme can lead to work stoppages, regulatory penalties, or contractual disputes that carry their own significant cost — a poor trade against the modest saving from underinvesting here.

Getting Preliminaries Right

• Tie the preliminaries budget explicitly to a realistic, not optimistic, project duration.
• Maintain adequate site security throughout, not just during the highest-risk delivery periods.
• Draw a clear, explicit boundary between preliminaries and mobilisation to avoid gaps or double-counting.
• Budget and reserve funds for end-of-project costs from the start, not as an afterthought.
• Resource safety compliance as a genuine investment, not a minimum-compliance formality.

A Practical Preliminaries Review Checklist

Before finalising any project's preliminaries figure, whether preparing it as a contractor or reviewing it as a client, a short structured review can catch most of the mistakes covered in this guide. Confirm the figure is built up from the project's realistic expected duration, not an optimistic best case, and that duration-linked items (management time, facility hire) are calculated against that realistic timeline. Check that site security provision is maintained consistently for the full project duration, not scaled back once initial risk feels lower.

Verify there is a clear, explicit boundary between what preliminaries covers and what mobilisation covers, with no item missing from both or duplicated across both. Confirm end-of-project costs — waste removal, final clean-up, demobilising remaining personnel — are included in the budget from the start rather than added as an afterthought once the project nears completion. Finally, check that safety compliance items are resourced as a genuine, adequate investment rather than priced at the bare minimum to make the overall figure look smaller.

Running through this checklist takes only a few minutes but catches the specific failure patterns responsible for most preliminaries-related budget overruns on Nigerian construction projects, making it a worthwhile discipline for any project regardless of scale.

Frequently Asked Questions

How can I tell if my preliminaries budget is realistic?

Build it up from the specific factors that drive cost — realistic project duration, actual workforce size, site-specific security and access needs — rather than applying a generic percentage, and cross-check the resulting figure against the typical percentage range for a sanity check.

What is the biggest single preliminaries cost driver on most projects?

Ongoing site management and supervision time is typically the largest single component on a project of meaningful duration, since it accrues continuously for as long as the project runs, unlike one-time items like initial safety induction or first-aid provisioning.

Should safety compliance costs ever be reduced to save budget?

No — safety compliance costs should be treated as a fixed, non-negotiable requirement rather than a variable to trim under budget pressure, given the disproportionate risk and potential cost of an incident relative to the modest saving from cutting corners here.

Who should carry out the preliminaries review checklist on a typical residential project?

For a self-build or small residential project, the homeowner or their appointed project manager can work through this checklist directly with the contractor; for a larger or more formal project, an independent quantity surveyor reviewing the preliminaries section as part of a wider cost check adds an extra layer of assurance beyond what the contracting parties alone might catch.

How often should preliminaries assumptions be revisited during a long project?

At minimum, whenever the project schedule is formally reviewed or revised, since preliminaries cost is so closely tied to duration — treating the original preliminaries figure as fixed and unchangeable throughout a project that has already visibly slipped its schedule is one of the quieter ways a budget overrun goes unnoticed until project completion.

What is the biggest single takeaway for a first-time client reviewing preliminaries?

Ask for an itemised breakdown built from realistic project-specific assumptions rather than accepting a single unexplained figure, and revisit that figure if the project's actual duration or scope changes materially — this single habit addresses the root cause behind most of the mistakes covered throughout this guide.

Does this guide's advice apply equally to commercial and residential Nigerian projects?

The underlying principles apply to both, though commercial projects typically involve larger, more formally documented preliminaries sections given their scale and the greater likelihood of institutional financing requiring detailed cost breakdowns — residential self-builders can still apply the same review discipline at a proportionally smaller, less formal scale.

What should I do if a contractor refuses to itemise preliminaries at all?

Treat this as a genuine warning sign and, where possible, seek a competing quote from a contractor willing to provide the detail — a persistent refusal to itemise a cost this significant is reasonable grounds to question the contractor's transparency more broadly, not just on this specific line item.

How does this guide relate to the mobilisation-focused guides published elsewhere on this site?

Preliminaries and mobilisation are closely related but distinct budget sections, and reading both together — this guide alongside our Mobilisation Calculator guides — gives a fuller picture of the full range of site-running costs that sit outside the direct measured construction works on a Nigerian building project.

Is there a simple rule of thumb to sanity-check a preliminaries figure quickly?

Comparing the quoted figure against the 3–8% of total construction cost range mentioned earlier in this guide is a reasonable quick sanity check, though it should never replace building the figure up from actual project-specific factors when time allows for a proper review.

What is the single most common regret clients express about preliminaries after a project finishes?

Not asking for an itemised breakdown at the outset is the most frequently cited regret, since clients who accepted a single lump-sum figure without question often later wonder, once the project is complete, whether it was fair — a question that a proper breakdown at the start would have answered proactively rather than leaving it as a lingering uncertainty.