Accurate estimating is the backbone of a successful construction project. Whether you’re a small contractor or a large building firm, one simple oversight in the early stages can lead to costly delays, budget overruns, or even the loss of a client’s trust. As a building estimating consulting firm in South Africa, we've seen firsthand how certain recurring mistakes can have major consequences.

In this article, we’ll explore 5 common estimating mistakes that could be hurting your business—and how to avoid them.

1. Underestimating Labour Costs

Labour often represents one of the most significant portions of any construction budget. Yet many contractors still rely on outdated rates, guesswork, or generic hourly figures without considering:

• Regional variations (e.g. Johannesburg vs. Durban)

• Skill level of workers required

• Overtime, weekends, or downtime

• Labour productivity based on job complexity

  
  

Solution: Use real-world, updated data. Track productivity on past projects and adjust future estimates accordingly. Outsourcing your estimating to professionals can also ensure labour is calculated based on current, local conditions.

2. Inaccurate Quantities in Take-Offs

A miscalculation in quantities can snowball into major cost overruns. For example, underestimating concrete volume or overestimating roof sheeting can result in wasted materials or site delays.

Common causes:

• Rushing the take-off process

• Relying on incomplete drawings

• Lack of familiarity with certain materials or construction methods

  
  

Solution: Use digital take-off software or consult experienced estimators to ensure quantities are precise. Accuracy at this stage prevents costly variations later on.

3. Ignoring Market Fluctuations in Material Prices

With global and local supply chains under pressure, South African material prices have seen rapid changes. Steel, timber, and cement prices can fluctuate monthly.

Mistake: Using outdated price lists or assuming stable costs over long project timelines.

Solution: Always request updated quotes from suppliers and allow for price escalation clauses in your estimates or contracts. Regularly monitor industry trends or partner with an estimating firm that does.

4. Excluding Preliminaries and Overheads

Contractors often focus only on the direct costs—materials and labour—while neglecting preliminaries like:

• Site setup

• Health and safety compliance

• Temporary fencing or toilets

• Transport, fuel, and security

  
  

Add to that fixed overheads like admin staff, insurances, and office costs, and you could be short-changing yourself significantly.

Solution: Build a standard checklist of preliminaries and overheads to include in every estimate. Better yet, get an expert to prepare or review your BOQ to ensure nothing is overlooked.

5. Failing to Allow for Risk and Contingency

No project goes exactly as planned. Weather delays, client changes, delivery issues, and unexpected ground conditions can all affect your bottom line.

Mistake: Not adding a contingency percentage or risk allowance in the estimate.

Solution: Depending on the project’s complexity, a 5–15% contingency is advisable. This gives you breathing room without having to renegotiate pricing mid-project.

🔧 How We Can Help

At Intellibuild, we specialise in accurate, reliable building estimates for contractors, developers, and project managers across South Africa. Our detailed take-offs and professional BOQs ensure that you quote confidently and competitively—without leaving money on the table.

If you’re tired of guesswork or losing out on tenders, get in touch with our consultation team.

🏗️ Final Thoughts

Estimating is more than just numbers—it's about strategy, foresight, and understanding the local market. By avoiding these 5 common mistakes, you protect your margins, win more work, and build stronger client relationships.

Let’s make every quote count.