5 Surprising Truths About Construction That Go Deeper Than a Foundation

Introduction: The Hidden Risks of Building

Starting a construction project, whether a home extension or a new development, often comes with a significant fear of the unknown. The most common anxieties revolve around unexpected costs and unforeseen delays that can derail even the most carefully planned budgets and timelines. Homeowners and developers alike worry about what might go wrong, but the reality is that the most critical factors for a project's success are often invisible.

The greatest risks aren't always visible in the architect's drawings or the builder's day rate. Instead, they are hidden underground in unpredictable soil, buried in the dense legal language of a contract, or simply assumed in conversations where clarity was never established. Professional construction is a discipline of proactive risk management, not reactive problem-solving.

This article reveals five of the most impactful truths from the construction industry. By understanding what happens beneath the surface—both literally and figuratively—you can learn to identify these hidden risks, ask the right questions, and adopt the professional risk-mitigation strategies that are essential to building smarter.

1. The Ground Is a Gamble, and the Contract Decides Who Pays for a Losing Hand

It's a common assumption that if a builder hits unexpected rock or contaminated soil, the client is automatically responsible for the extra cost. However, the legal reality is often the complete opposite. Under many standard UK construction contracts, such as the JCT forms, the default position at common law places the risk of encountering unforeseen ground conditions squarely on the contractor. This legal precedent strategically forces the party with the most expertise—the contractor—to perform due diligence, protecting the less-informed client from risks the contractor is best positioned to foresee.

In this context, "unforeseeable" has a specific legal meaning. It doesn't just mean something the client didn't expect; it means a condition that an experienced contractor could not have reasonably predicted based on the information provided to them at the tender stage. This contractual principle underscores why contractors must conduct their own due diligence rather than relying on blind confidence.

Because the contractor carries this significant risk, preliminary site and soil investigations are not optional extras but essential investments for everyone involved. A typical investigation costing around £700–£1,300 is a mandatory risk-mitigation step that can save thousands in potential disputes and delays. It provides the data needed for contractors to price the job accurately and for clients to have confidence in the budget.

“…if the contractor ought, prudently and properly, to have full information of the nature of the work he is preparing to undertake, and the advice of a skilful person is necessary to enable him to understand the specification, is it any reason for not employing such a person that it would add to the expense of the contractor before making his tender? It is also said that it is the usage of contractors to rely on the specification, and not to go examine it particularly for themselves. If so, it is an usage of blind confidence of the most unreasonable description…”

2. Your Postcode and Soil Type Can Drive Costs More Than Your Builder's Rate

While clients often focus on negotiating a builder's daily rate, the two non-negotiable, site-specific realities that form the baseline cost of a project before a single builder is hired are geology and geography.

Geography: Where you build has a dramatic impact on the final budget. Construction costs in London and the South East are typically 15% to 30% higher than in other UK regions like the Midlands or the North. This regional premium affects everything from material transport to labour wages, directly influencing the total project expenditure.

Geology: The ground beneath your feet can be an even more significant cost factor. In Essex, for example, the predominant "London Clay" soil has a high shrinkage potential. Building control authorities there often specify a minimum foundation depth of 1 metre, compared to the national average of 750mm. This single geological factor can increase excavation and concrete costs by 30-40% before any other work begins. Similarly, a site with restricted access can force a reliance on manual labour or specialized mini-excavators, potentially increasing labour costs by 25-40%.

3. A 15% Contingency Fund Isn't a Sign of Failure—It's a Mark of Professionalism

Many view a contingency fund as a budget line for when things go wrong. In groundworks, however, it's a mandatory budgeting tool for managing the inherent uncertainty that comes with working below the surface. The simple truth is that no one can know with 100% certainty what lies underground across an entire site.

Industry best practice is to allocate a dedicated contingency of 10% to 15% of the groundworks budget specifically to cover unforeseen conditions. For a typical extension with a groundworks package of £10,000-£15,000, this means professionally setting aside £1,000-£2,250 from the outset. This isn't padding the budget; it's a crucial financial buffer against the unknown.

A transparent, professional contractor will discuss this contingency requirement upfront. It gives both the client and the construction team peace of mind, ensuring that if an unexpected issue arises—such as hitting an old foundation or dealing with a high water table—there is a pre-agreed financial plan to address it without causing project delays or stressful, unexpected cash calls. Clients are often thankful later that this buffer was planned from the start.

4. Great Communication Isn't a Soft Skill; It's a Hard System

In construction, poor communication is a leading cause of project failure, creating disputes, delays, and budget overruns. Effective client-contractor communication is not about casual chats or occasional phone calls; it's a structured, systematic process designed to produce clarity and build trust. This system has three key components:

1. Describe the Process: A professional contractor educates the client on how their company works. They should walk the client through every key stage, from how the initial estimate is developed to the major milestones of the production phase and how information moves through the chain of command.

2. Define the Terms: The construction world is filled with jargon that can be confusing to clients. A great contractor takes the time to clearly define key contractual terms so both parties understand their rights and obligations. Common terms that require clear definition include:

   • Allowance: Is the allowance included in the price quote or is it in addition to the price? Does the allowance include tax? Does it also include installation labor? What happens if I choose something above/below the allowance?

   • Change Order: What is a Change Order? When will I know a Change Order is happening? How much are Change Orders? When do I pay for the Change Order? What happens if I don’t approve a Change Order?

   • Substantial Completion: What does substantial completion mean? How much or what kind of work remains at substantial completion? Is there a payment due upon substantial completion?

   • Punch List: What is a punch list? Why do you need to do a punch list? Who is responsible for creating the punch list?

3. Designate the Methods: A formal process for communication and transactions is essential. This includes designating a single point of contact, establishing the best way to communicate (email, phone), and agreeing on a format for updates, such as weekly one-page progress reports with photos. This systematic approach ensures information is consistent, documented, and clear.

Do not assume clarity. Produce it.

5. The Real Pros Carry Proof: Why a CSCS Card Matters

The stereotype of the casual, unregulated builder is increasingly outdated. Today's professional construction industry is focused on verifiable standards, safety, and competence. One of the clearest indicators of this professionalism is the CSCS (Construction Skills Certification Scheme) card.

A CSCS card is not just an ID; it is evidence that the individual holding it is professionally trained and qualified for their specific role on a construction site. It proves they have the required skills and have passed a health, safety, and environment test. Leading firms demonstrate a deeper commitment by ensuring the right certification for the right role. Mackoy Ltd, a major groundworks contractor, is a prime example: every single one of its over 300 operatives is CSCS (for general skills) or CPCS (for plant operators) verified and must present their card simply to gain entry to the worksite each morning.

Beyond certifications, other signs of a professional operation are non-negotiable legal requirements. Any contractor with employees must, by law, have Employers Liability insurance with a minimum coverage of £5 million. Asking for proof of these credentials is not being difficult; it's a basic due diligence step that separates the true professionals from the rest.

Conclusion: Building on a Foundation of Knowledge

Successful construction projects are rarely the result of luck. They are built not just on concrete and steel, but on a solid foundation of diligence, systematic communication, and a clear-eyed understanding of risk. The most critical work happens long before the first trench is dug—in site investigations, in contract negotiations, and in establishing transparent processes.

These five truths are not just industry trivia; they are the essential components of a professional risk-mitigation strategy. They empower you to move beyond common assumptions and take control of your project's destiny. The quality of a building starts with the ground it stands on, but the success of the entire project starts with the quality of the questions you ask.

Now that you know what's really involved, are you asking the right questions to ensure your project is built on solid ground?