5 reasons for budget overruns and how to avoid them

Many overruns originate well before construction begins. They result from site conditions that haven't been fully investigated, compliance requirements that haven't been accounted for, changes to the design or estimates based on incomplete information.

Understanding these risks early allows businesses to make more informed decisions and establish a realistic budget before committing capital.

Here are five common causes of commercial building budget overruns, and how to manage them.

5 reasons behind budget overruns

1. Compliance and Resource Conditions

The site you choose has a significant influence on what your development will cost.

Zoning, access requirements, traffic movements, stormwater management and local council regulations can all introduce additional work and expense. These requirements may not be immediately obvious when assessing a property's suitability.

For example, one Attika client was required to construct a pull-off bay from a state highway to provide access to their property. This introduced an unexpected cost during the early planning stages.

On another workshop project, two protected trees needed to be removed to accommodate the proposed building. Resource consent conditions subsequently required a substantial number of replacement trees to be planted, adding to the development cost.

Firefighting water supply, stormwater infrastructure and other compliance requirements can also have significant financial implications.

How to manage the risk

Assess the planning and compliance requirements before finalising the site purchase or development budget.

This means involving the appropriate planning, civil engineering and design expertise early enough to identify potential constraints and understand their cost implications.

Where additional approvals or infrastructure may be required, those costs need to be reflected in the financial assessment of the development.

2. UNEXPECTED Ground Conditions

Ground conditions are among the most significant sources of financial uncertainty in commercial construction.

Uncompacted fill, buried rubbish, contaminated land and poor ground-bearing capacity can require additional engineering, foundation work or remediation.

These costs can be substantial, particularly where the site has previously been used for activities associated with contamination under the Hazardous Activities and Industries List (HAIL).

A geotechnical report is an important part of assessing these risks, but the level of investigation matters.

In one New Zealand project, an initial geotechnical report prepared for a property purchase indicated good ground-bearing capacity. However, that investigation was not sufficiently detailed for construction.

A subsequent investigation identified ground issues outside the scope of the original report, resulting in more than $100,000 in remediation costs.

The initial findings were not necessarily incorrect. The problem was relying on a limited investigation to provide a level of certainty it was never intended to deliver.

How to manage the risk

Establish what level of geotechnical investigation is required for the proposed building, rather than relying solely on a preliminary property assessment.

The geotechnical, structural and civil engineering teams should work together to understand how ground conditions affect foundations, earthworks, drainage and the overall construction cost.

Where uncertainty remains, it should be identified and accounted for in the project budget.

3. Finished Floor Level and Site Works

The finished floor level (FFL) of a commercial building affects far more than the height of the floor.

Flood risk, stormwater requirements, earthworks restrictions, vehicle access and the surrounding site levels can all influence where the building needs to sit.

Council requirements may also change during a project's development. If flood levels or other planning requirements are revised, the design may need to be adjusted, potentially increasing costs.

A site that appears straightforward can become more complex once drainage, accessways, hardstands and earthworks are considered together.

For example, lowering the finished floor level might reduce the amount of fill required beneath the building. However, that decision can create additional costs elsewhere if there is insufficient fall for stormwater drainage or if surrounding hardstands require redesign.

A saving in one part of the project can become an expense in another.

How to manage the risk

Consider the entire site when making decisions about building levels and earthworks.

Civil engineers, structural engineers, designers and cost managers need to assess how changes affect drainage, access, foundations and external works.

The objective should be to establish the most commercially effective solution for the complete development, rather than reducing the cost of an individual component.

4. Design Scope Creep

Scope creep occurs when the requirements or specifications of a project change after the initial budget has been established.

These changes may involve additional floor area, higher specifications, extra building services, changes to the office layout or new operational requirements.

Individually, the additions may appear manageable. Collectively, they can materially increase the total investment.

Some changes are worthwhile. Higher-quality cladding, for example, may improve the building's appearance, durability and long-term value.

However, more expensive materials or architectural details do not automatically deliver a corresponding commercial benefit.

A premium wall or roof cladding specification may add considerable cost without meaningfully improving the building's performance, appearance or value.

Similarly, decisions about racking, floor loading, mezzanines, fire protection or equipment can affect several parts of the building at once.

The challenge is understanding the full cost of each decision before it becomes part of the design.

How to manage the risk

Establish a clear project brief that defines the building's operational requirements, performance expectations and investment parameters.

Design decisions should then be assessed against those objectives, with cost information available throughout the process.

Where changes are proposed, consider their effect on the overall development, including engineering, compliance, procurement and programme.

This allows businesses to make deliberate investment decisions rather than discovering their financial impact after the design has progressed.

5. Inaccurate project estimates

A project budget can only be relied upon if it reflects the actual scope, site conditions and construction requirements.

Early estimates are useful for assessing feasibility, but they are not the same as a fully developed construction price.

Costs vary according to location, ground conditions, building specifications, materials, labour availability and the complexity of the project.

An estimate based on general square-metre rates may not adequately account for these variables.

The programme also matters. Unrealistic construction schedules, late procurement decisions or insufficient time to obtain competitive pricing can introduce additional cost.

For a business making a significant capital investment, the distinction between an indicative estimate and a well-substantiated price is important.

A figure may appear affordable at the feasibility stage but become considerably less attractive once the full scope has been established.

How to manage the risk

Develop the budget alongside the design, using current market information and input from people who understand the practical requirements of construction.

Quantity surveyors, professional estimators, engineers, suppliers and contractors all have a role in establishing reliable cost information.

As the design progresses, the estimate should be reviewed against the developing scope, with assumptions, exclusions and outstanding decisions clearly identified.

The objective is to progressively reduce uncertainty until the business has a reliable understanding of the total investment required.

Strategies to Avoid Budget Blowouts

The five risks above share a common theme: decisions made in isolation, or without sufficient information, can create costs elsewhere in the project.

Managing those risks requires a coordinated approach to planning, design, engineering and construction.

For business owners and developers, the following measures are particularly important:

• Investigate the site early. Understand ground conditions, planning constraints, infrastructure requirements and potential contamination before committing significant capital.
• Define the operational brief. Establish how the building needs to function, including equipment, vehicle movements, storage, staff facilities and future expansion.
• Develop design and cost together. Test design options against realistic construction costs rather than waiting until the drawings are complete.
• Understand the full scope. Identify exclusions, provisional allowances, assumptions and any work that sits outside the proposed construction price.
• Assess the wider implications of changes. A decision affecting one part of the building may also influence engineering, compliance, site works or programme.
• Allow for genuine uncertainty. Where risks cannot yet be resolved, establish appropriate contingencies and a clear process for managing them.
• Maintain clear accountability. Ensure responsibility for coordinating consultants, design decisions, cost information and construction delivery is clearly established.

These measures help protect the financial assumptions on which the development is based.

Why a fixed price alone may not prevent budget overruns

A fixed-price construction contract can provide valuable cost certainty, but that certainty depends on the scope and conditions behind the agreed figure.

If ground conditions remain unknown, specifications are incomplete or substantial work has been excluded, the total development cost may still change.

Variations can also arise when the client changes the scope or when circumstances trigger additional payment under the contract.

This is why understanding the assumptions, exclusions and unresolved risks is as important as understanding the headline price.

For a commercial building project, the objective should be to establish a reliable total investment figure, supported by a clearly defined scope and a transparent approach to managing any remaining risks.

How Attika approaches cost certainty

At Attika, we bring planning, design, engineering, cost management and construction expertise together to establish a clearer understanding of the project before major capital commitments are made.

Our integrated approach allows site constraints, compliance requirements, structural options and operational needs to be assessed alongside construction costs.

Rather than developing a design in isolation and pricing it at the end, we consider buildability, commercial implications and the overall investment throughout the process.

This forms the foundation of Attika's Total Maximum Investment (TMI) approach, which is designed to give clients greater clarity over the capital required to deliver their project.

With one coordinated team responsible for the development process, clients benefit from clearer accountability and better-informed decisions at each stage.

The bottom line

Budget overruns can have consequences well beyond the construction site. They can affect financing, cashflow, operational readiness and the long-term performance of the asset.

The most effective way to manage that exposure is to identify and resolve the major cost variables before committing to construction.

For businesses investing in a new commercial or industrial facility, the quality of the planning, design and cost information behind the price is fundamental to protecting the investment.

Planning a commercial or industrial development?

Talk to Attika about establishing a realistic project budget and understanding the risks that could affect your investment.